JP6880099B2 - Radiation imaging system, image processing device, radiation imaging system control method, and radiation imaging system control program - Google Patents

Description

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

Conventionally, as a radiographic image capturing apparatus for photographing a subject, for example, a radiographic imaging apparatus for performing radiographic imaging for the purpose of medical diagnosis is known. The radiation imaging device captures a radiation image by detecting the radiation emitted from the radiation irradiation device and transmitted through the subject. The radiation imaging apparatus captures a radiation image by collecting and reading out the electric charges generated in response to the irradiated radiation.

There is known a technique for photographing a large subject, for example, a long subject, using a plurality of radiographic image capturing devices. When a plurality of radiographic imaging devices are arranged adjacent to each other, the ends (part) of the radiographic imaging devices are overlapped and overlapped so as not to cause defects in the radiographic image in the adjacent portions. There is.

In the overlapping portion of the captured radiographic image, a step component due to the step at the end of the radiographic image capturing device is generated and appears as a step artifact.

Therefore, for example, in Patent Document 1, the brightness of a radiation image obtained by photographing a subject is corrected by using a correction coefficient obtained from brightness data representing the shading of an image obtained by X-ray photography of a reference subject. Therefore, the description for correcting the decrease in the brightness of the overlapping region of the radiographic imaging apparatus is described.

Further, Patent Document 2 describes a technique for suppressing a brightness fluctuation generated in an overlapping portion and facilitating image processing after imaging by devising an overlapping method (overlapping region) of a radiation imaging apparatus. ing.

Japanese Unexamined Patent Publication No. 2000-278607 Japanese Unexamined Patent Publication No. 2000-292546

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

The present disclosure has been made to solve the above problems, and 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. It is an object of the present invention to provide a radiation imaging system, an image processing device, a control method of the radiation imaging system, and a control program of the radiation imaging system, which can be appropriately performed.

In order to achieve the above object, the radiation imaging system of the present disclosure is generated according to a first conversion layer that converts radiation incident from a radiation irradiation device into light and a light converted by the first conversion layer. A first radiation imaging device that captures a first radiation image including a first substrate on which a plurality of first pixels that accumulate charges are formed, and a side farther from the radiation irradiation device than the first radiation imaging device. , A second conversion layer that is arranged in a state where a part of it is overlapped with respect to the incident direction of the radiation and converts the radiation into light, and a plurality of that accumulates the charge generated according to the light converted by the second conversion layer. A second radiation imaging apparatus for capturing a second radiation image, and a second radiation image capturing apparatus for capturing a second radiation image, and a first radiation image and a second radiation image are obtained with respect to the second radiation image. Of the conversion layer steps indicated by the conversion layer step component caused by the first conversion layer of the first radiation imaging apparatus, the overlap region in which the image information exists in the first radiation image is overlaid on the first radiation image. performs correction for low reducing the conversion layer step by diverting an image of a region corresponding to the overlapped region, also the substrate step indicated substrate stepped component generated due to the first substrate of the first radiation image capturing apparatus, A correction unit that reduces the density difference between the density of the substrate step component and the density of the normal component corresponding to the image in the region other than the conversion layer step component and the substrate step component in the second radiation image. And.

The correction unit of the radiation imaging system of the present disclosure derives a correction amount for smoothly connecting the diverted first radiation image and the conversion layer step in a region different from the overlap region among the conversion layer step components. , The correction may be performed by the derived correction amount.

The correction unit of the radiation imaging system of the present disclosure may correct the step of the conversion layer after correcting the step of the substrate.

Further, the image processing apparatus of the present disclosure includes a first conversion layer that converts radiation incident from a radiation irradiation device into light, and a plurality of first conversion layers that accumulate charges generated in response to the light converted by the first conversion layer. A first radiation image taken by a first radiation imaging apparatus provided with a first substrate on which one pixel is formed, and a side farther from the radiation irradiation apparatus than the first radiation imaging apparatus, in the direction of radiation incident. On the other hand, a second conversion layer that is arranged in a partially overlapped state and converts radiation into light, and a plurality of second pixels that accumulate charges generated in response to the light converted by the second conversion layer are formed. The second radiation image taken by the second radiation imaging apparatus provided with the second substrate is acquired, and the second radiation image is caused by the first conversion layer of the first radiation imaging apparatus. Among the conversion layer steps indicated by the generated conversion layer step components, the conversion layer step is obtained by diverting the image of the region corresponding to the overlap region of the first radiation image for the overlap region in which the image information exists in the first radiation image. The density of the substrate step component, the conversion layer step component in the second radiation image, and the substrate step component indicated by the substrate step component caused by the first substrate of the first radiation imaging apparatus are corrected. It is provided with a correction unit that performs correction by reducing the density difference from the density of the normal component corresponding to the image of the region other than the step component of the substrate.

Further, in the control method of the radiation imaging system of the present disclosure, a first conversion layer that converts radiation incident from a radiation irradiation device into light and a charge generated in response to the light converted by the first conversion layer are accumulated. A first radiation imaging device that captures a first radiation image including a first substrate on which a plurality of first pixels are formed, and a radiation source that is farther from the radiation irradiation device than the first radiation imaging device. A second conversion layer that is arranged in a state of being partially overlapped with respect to the incident direction and converts radiation into light, and a plurality of second conversion layers that accumulate charges generated in response to the light converted by the second conversion layer. A control method for a radiation imaging system including a second substrate on which pixels are formed and a second radiation imaging apparatus for capturing a second radiation image, the first radiation image and the second radiation image. Of the steps shown by the step component of the conversion layer step caused by the first conversion layer of the first radiation imaging apparatus for the second radiation image, the image information is included in the first radiation image. for the overlap area exists, the conversion layer step by diverting an image of an area corresponding to the overlapping region of the first radiation image subjected to correction for low reduction and also to the first substrate of the first radiation image capturing apparatus The concentration of the substrate step component indicated by the resulting substrate step component is the concentration of the substrate step component and the concentration of the normal component corresponding to the image of the region other than the conversion layer step component and the substrate step component in the second radiation image. It includes a step of making a correction that reduces the difference by reducing the difference.

Further, the control program of the radiographic imaging system of the present disclosure is for causing a computer to execute each step of the control method of the present disclosure.

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

It is a schematic block diagram which shows the schematic structure of an example of the radiation 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 including various corrections which concerns on this Embodiment. It is a block diagram which shows an example of the structure of the radiation imaging apparatus which concerns on this embodiment. It is a line sectional view of an example of the pixel of the radiation detector which concerns on 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 shows the state seen from the side. It is explanatory drawing for demonstrating the relationship between the radiation irradiation apparatus and an electronic cassette which concerns on this Embodiment, and shows a radiation imaging apparatus seen from the radiation irradiation apparatus side. It is explanatory drawing for demonstrating the relationship between the radiation irradiation apparatus and an electronic cassette which concerns on this Embodiment, and shows the state which the radiation imaging apparatus moved (moved) in FIG. 5B. It is explanatory drawing for demonstrating the radiation image taken by each radiation image taking apparatus which concerns on this Embodiment. (1) shows a radiation image taken by the upper radiation imaging apparatus. (2) shows a radiation image taken by the lower radiation imaging device. It is explanatory drawing for demonstrating the change of the position of the cinch step component and the glass step component which concerns on this embodiment. (1) shows a case where the angle of the radiation X incident on the imaging region is different. (2) shows the case where the radiographic imaging apparatus moves (moves). It is a flowchart which showed an example of the flow of the image processing which corrects the photographed image photographed by the upper radiation image capturing apparatus which concerns on this embodiment. It is a flowchart which showed an example of the flow of the image processing which corrects the photographed image photographed by the lower radiation image capturing apparatus which concerns on this embodiment. It is a schematic diagram for demonstrating an example of the flow of image processing which corrects the photographed image photographed by the lower radiation image capturing apparatus which concerns on this Embodiment. It is a schematic block diagram for demonstrating an example in which a plurality of electronic cassettes are arranged adjacent to each other. It is a schematic block diagram for demonstrating another example in which a plurality of electronic cassettes are arranged adjacent to each other.

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

First, a schematic configuration of the entire radiation imaging system including the radiation 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 the radiation imaging system of the present embodiment. In the radiation imaging system 10 of the present embodiment, the electronic cassette 12 includes a plurality of radiation imaging devices 14.

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

Further, 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) or a radiographic image interpretation device (not shown) of the console 20 to display a doctor. It has a function to make a radiologist interpret a radiological image. The radiation image reading device (not shown) is a device having a function for the image reader to read the captured radiation image, and is not particularly limited, but is a so-called image interpretation viewer, display, mobile terminal, and tablet. Examples include terminals.

The radiation imaging system 10 of the present 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 a target portion of a subject 18 with radiation X from a tube (not shown) which is a radiation irradiation source under the control of the console 20. The radiation irradiation device 16 includes an operation input unit for the user to manually set radiation X irradiation conditions such as tube voltage, tube current, and irradiation time directly to the radiation irradiation device 16, and set irradiation. A display unit for displaying conditions and the like may be provided. Further, the radiation irradiation device 16 transmits information indicating the manual setting, the set value by the manual setting, and the current status (standby state, ready state, exposure in progress, end of exposure, etc.) 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 that has passed through the subject 18 irradiates the electronic cassette 12. The radiographic imaging apparatus 14 of the electronic cassette 12 has a function of generating electric charges according to the dose of radiation X transmitted through the subject 18 and generating and outputting image information indicating a radiographic image based on the amount of electric charges generated. Have. In the present embodiment, generating and outputting image information is called photographing. The electronic cassette 12 of the present embodiment, in the housing 13, a plurality of radiographic image capturing apparatus 14 ₍₁₄ 1 to 14 ₃₎ (described in detail later).

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

The console 20 of this embodiment is a server computer. FIG. 2 shows an example of a schematic configuration diagram of a 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, and I /. It includes an F unit 44 and a storage unit 50.

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 the ROM in advance. The RAM has a function of temporarily storing various data, and the HDD has a function of storing and holding various data. In addition, the control unit 30 functions as a correction image acquisition unit and a captured image acquisition unit. Further, the control unit 30 has a function of performing image processing including various corrections on various images.

The display unit drive unit 32 has a function of controlling the display of various information on the display unit 34. The display unit 34 of the present embodiment has a function of displaying a photographing menu, a photographed radiation 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 for the user to input a processing operation related to taking a radiation image and image processing of the photographed radiation image. The operation input unit 38 may have the form of a keyboard as an example, or may have the form of a touch panel integrated with the display unit 34. Further, the operation input unit 38 may include a camera and may have a form of inputting various instructions 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 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 information between the radiation imaging device 14 and the radiation irradiation device 16.

The storage unit 50 has a function of storing a photographed image, a gain caliber image, 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 to each other so that information and the like can be exchanged via a bus 46 such as a system bus or a control bus. Has been done.

Next, a schematic configuration of the electronic cassette 12 of the present embodiment will be described. The electronic cassette 12 includes a plurality of radiographic imaging devices 14. In this embodiment, as a specific example, as shown in FIG. 1, there will be described a case where the electronic cassette 12 is provided with three radiographic imaging device 14 (14 1 _{to 14 3),} radiation The number of image capturing devices 14 is not limited to this embodiment. Incidentally, referred to as the radiographic imaging apparatus 14 in the case of when or collectively radiographic apparatus ₁₄ 1, 14 _2, and does not distinguish between 14 _3.

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

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

FIG. 3 shows a configuration diagram showing an example of the configuration of the radiation imaging apparatus 14 according to the present embodiment. In the present embodiment, a case where the present invention is applied to an indirect conversion type radiation imaging apparatus 14 in which radiation such as X-rays is once converted into light and the converted light is converted into electric charges will be described. In FIG. 3, the scintillator 98 (see FIG. 4) that converts radiation into light is omitted.

The radiation imaging device 14 of the present 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 is a sensor unit 103 that receives light to generate an electric charge and accumulates the generated electric charge, and a TFT (Thin Film Transistor) switch 74 that is a switch element for reading out the electric charge accumulated in the sensor unit 103. The pixel 100 is configured to include and. In the present embodiment, the sensor unit 103 generates an electric charge by being irradiated with the 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 an intersecting direction with respect to the gate wiring direction (signal wiring direction in FIG. 3). In FIG. 3, the arrangement of the pixels 100 is shown in a simplified manner. For example, 1024 pixels × 1024 pixels 100 are arranged in the gate wiring direction and the signal wiring direction.

Further, 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 charge accumulated in the sensor unit 103 intersect with each other. Is provided. In the present embodiment, one signal wiring 73 is provided for each pixel row in one direction, and one gate wiring 101 is provided for each pixel row in the intersecting direction. For example, when 1024 x 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. One end and the other end of the common electrode wiring 95 are connected in parallel, and one end is 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. By flowing the control signal through each gate wiring 101 in this way, 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 according to the switching state of the TFT switch 74 of each pixel 100. More specifically, an electric signal corresponding to the amount of electric charge accumulated by turning on the TFT switch 74 of any of the pixels 100 connected to the signal wiring 73 flows through each signal wiring 73.

A signal detection circuit 105 for detecting an electric signal flowing out to each signal wiring 73 is connected to each signal wiring 73. Further, a scan signal control circuit 104 that outputs a control signal for turning on / off the TFT switch 74 is connected to each gate wiring 101. In FIG. 3, the signal detection circuit 105 and the scan signal control circuit 104 are simplified into one, but for example, a plurality of signal detection circuits 105 and scan signal control circuits 104 are provided and a predetermined number (for example, 256) is provided. The signal wiring 73 or the gate wiring 101 is connected every time. For example, when the signal wiring 73 and the gate wiring 101 are provided by 1024 lines each, four scan signal control circuits 104 are provided to connect the gate wiring 101 by 256 lines, and four signal detection circuits 105 are also provided and 256 lines are provided. The signal wiring 73 is connected one by one.

The signal detection circuit 105 includes an amplifier circuit (not shown) that amplifies the input electric signal for each signal wiring 73. In the signal detection circuit 105, the electric signal input from each signal wiring 73 is amplified by an amplifier circuit and converted into a digital signal by an ADC (analog-to-digital converter).

The signal detection circuit 105 and the scan signal control circuit 104 are subjected to predetermined processing such as noise removal on the digital signal converted in the signal detection circuit 105, and the signal detection timing is indicated 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 is connected to the scan signal control circuit 104.

The control unit 106 of the present embodiment is a microcomputer, and includes a non-volatile storage unit including a CPU (central processing unit), ROM and RAM, flash memory, and the like (not shown). The control unit 106 controls for taking a radiation image by executing the program stored in the ROM on 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 on which the gate wiring 101 and the gate electrode 72 are formed (hereinafter, also referred to as “first signal wiring layer”) is formed by 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 of the first signal wiring layer, and a portion located on the gate electrode 72 acts as a gate insulating film in the TFT switch 74. The insulating film 85 is made of, for example, SiNx or the like, and is formed by, for example, a 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.

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

In order to protect the TFT switch 74 and the signal wiring 73, a TFT protective film layer 88 covers almost the entire surface (almost the entire area) of the area on the substrate 71 where the pixels 100 are provided so as to cover the second signal wiring layer. It is formed. The TFT protective film layer 88 is made of, for example, SiNx or the like, and is formed by, for example, CVD film formation.

A coating type interlayer insulating film 82 is formed on the TFT protective film layer 88. The interlayer insulating film 82 is a base polymer composed of a photosensitive organic material having a low dielectric constant (relative permittivity εr = 2 to 4) (for example, a positive photosensitive acrylic resin: a copolymer of methacrylic acid and glycidyl methacrylate). It is formed with a film thickness of 1 to 4 μm by a material mixed with a naphthoquinone diazide-based positive photosensitizer.

In the TFT glass substrate 90 according to the present embodiment, the interlayer insulating film 82 keeps the capacitance between the metals arranged in the upper layer and the lower layer of the interlayer insulating film 82 low. Further, in general, such a material also has a function as a flattening film, and also has an effect of flattening a step in the lower layer. 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. There is. When the semiconductor layer 91, which will be described later, is as thick as about 1 μm, the lower electrode 81 has almost no limitation on the material as long as it has conductivity. Therefore, there is no problem if it is formed by 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), the semiconductor layer 91 does not absorb enough light, so that the leakage current due to light irradiation to the TFT switch 74 is prevented from increasing. It is preferable to use an alloy mainly composed of a light-shielding metal or a laminated film.

A semiconductor layer 91 that functions as a photodiode is formed on the lower electrode 81. In the present embodiment, as the semiconductor layer 91, a PIN structure photodiode in which n + layer, i layer, and p + layer (n + amorphous silicon, amorphous silicon, p + amorphous silicon) are laminated is adopted. The semiconductor layer 91 is formed by laminating n + layer 91A, i layer 91B, and p + layer 91C in this order from the lower layer. The i-layer 91B is irradiated with light to generate electric charges (a pair of free electrons and free holes). The n + layer 91A and the p + layer 91C function as a contact layer, and electrically connect the lower electrode 81, the upper electrode 92 described later, and the i layer 91B.

Upper electrodes 92 are individually formed on each semiconductor layer 91. For the upper electrode 92, a material having high light transmission 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 an upper electrode 92, a semiconductor layer 91, and a lower electrode 81.

A coating-type interlayer insulating film 93 is formed on the interlayer insulating film 82, the semiconductor layer 91, and the upper electrode 92 so as to have an opening 97A in a part corresponding to the upper electrode 92 and to cover each semiconductor layer 91. There is.

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. A contact pad 97 is formed in the vicinity of the opening 97A of the common electrode wiring 95, and the common electrode wiring 95 is electrically connected to the upper electrode 92 via the opening 97A of the interlayer insulating film 93.

A protective film is formed on the TFT glass substrate 90 thus formed with an insulating material having a lower light absorption, if necessary, and radiation conversion is performed on the surface thereof using an adhesive resin having a low light absorption. The scintillator 98, which is a layer, is attached. Alternatively, the scintillator 98 is formed by the vacuum deposition method. As the scintillator 98, a scintillator that generates fluorescence having a relatively wide wavelength region so as to be able to generate light in an absorbable wavelength region is desirable. Examples of such a scintillator 98 include CsI: Na, CaWO _{4 , YTaO 4} : Nb, BaFX: Eu (X is Br or Cl), LaOBr: Tm, GOS and the like. Specifically, when imaging using X-rays as radiation X, those containing cesium iodide (CsI) are preferable, and CsI: Tl (talium 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. The emission peak wavelength of CsI: Tl in the visible light region is 565 nm. When a scintillator containing CsI is used as the scintillator 98, it is preferable to use a scintillator formed as a strip-shaped columnar crystal structure by a vacuum vapor deposition method.

As shown in FIG. 4, the radiation detector 26 is irradiated with the radiation X from the side where the semiconductor layer 91 is formed, and reads the radiation image by the TFT glass substrate 90 provided on the back surface side of the incident surface of the radiation X. In the case of the so-called back surface reading method (PSS (Penetration Side Sampling) method), more intense light is emitted on the upper surface side of the scintillator 98 provided on the semiconductor layer 91 in the same 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 incident surface of the radiation X. In this case, the radiation X transmitted through the TFT glass substrate 90 is incident on the scintillator 98, and the TFT glass substrate 90 side of the scintillator 98 emits more intense light. The sensor unit 103 of each pixel 100 provided on the TFT glass substrate 90 is charged by the light generated by the scintillator 98. Therefore, in the radiation detector 26, the light emitting position of the scintillator 98 with respect to the TFT glass substrate 90 is closer to the TFT glass substrate 90 in the case of the front surface reading method than in the case of the back surface reading method, so that the resolution of the radiation image obtained by photographing is obtained. Is high.

The radiation detector 26 is not limited to the one shown in FIGS. 3 and 4, and can be modified in various ways. For example, in the case of the back surface reading method, since the possibility of radiation X reaching is low, instead of the above-mentioned one, another imaging element such as a CMOS (Complementary Metal-Oxide Semiconductor) image sensor having low resistance to radiation X can be used. It may be combined with a TFT. Further, it may be replaced with a CCD (Charge-Coupled Device) image sensor that transfers charges while shifting them by a shift pulse corresponding to the gate signal of the TFT.

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

Next, the radiographic imaging apparatus 14 in the electronic cassette 12 of the present embodiment will be described. In the following, as a specific example, a case where the ISS type radiation image capturing apparatus 14 is used will be described. 5A to 5C show explanatory views 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 a radiation imaging device 14 seen from the radiation irradiation device 16 side. FIG. 5C shows a state in which the radiation imaging apparatus 14 has moved (moved) in FIG. 5B. Note that in FIGS. 5A to 5C, the description of the housing 13 is omitted.

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

Further, as a specific example, in the radiation imaging apparatus 14 of the present embodiment, the TFT glass substrate 90 is larger than the scintillator 98, as shown in FIG. 5A. More specifically, the area of the TFT glass substrate 90 facing the radiation irradiation device 16 is larger than that of 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, as shown in FIG. 5A, the electronic cassette 12 is adjacent to the end (part) of the imaging region of the radiographic imaging apparatus 14 due to the reasons (1) to (3) below. The end portions of the radiographic imaging apparatus 14 to be used are overlapped and arranged. Specifically, the imaging regions are overlapped so as to overlap with respect to the incident direction of the radiation X.

(1) If there is a gap between the imaging regions of each radiographic imaging apparatus 14, there may be a portion of the subject 18 that is not imaged. In this case, the radiation image capturing apparatus 14 _{1-14 3} long which connect the captured radiographic image in each of the radiographic images (the electronic cassette 12 overall radiographic image), so that the defects.

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

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

(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, each radiographic imaging device 14 is fixed to the housing 13, while the radiographic imaging devices 14 are arranged without being fixed to each other. Since they are not fixed to each other, the radiation imaging device 14 (radiation detector 26) moves (moves, see FIG. 5C).

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

As shown in FIG. 5A, in the radiation imaging system 10 of the present embodiment, the position of the radiation irradiation device 16 can be moved in a direction along the long direction of the electronic cassette 12. Therefore, the position of the irradiation device 16 differs depending on the imaging site of the subject 18 (see FIG. 1) to be imaged, the type of imaging, and the like, and the position of the electronic cassette 12 relative to the long imaging region is displaced. .. Therefore, the angle of the incident radiation X differs in each radiation imaging device 14 depending on the position of the radiation irradiation device 16. 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 obliquely incident (obliquely entered) with respect to the imaging region. Further, as shown in FIG. 5C, when the radiation imaging apparatus 14 moves (moves), the imaging area of the overlapping portion changes.

In consideration of various cases such as these, in the electronic cassette 12 of the present embodiment, the range of the photographing area of the overlapping portion is defined with a margin so that the overlapping of the photographing areas is not eliminated.

In the electronic cassette 12 of the present embodiment, as shown in FIG. 5A, as a specific example, the radiation image capturing apparatus 14 ₁ and 14 ₃ are viewed from above (radiation irradiation device 16 side upper, 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.

If the signal detection circuit 105 is provided so as to be sandwiched between the radiation image capturing devices 14, the signal detection circuit 105 may be reflected in the radiation image, as in the present embodiment. , It is preferable to superimpose the signal detection circuits 105 so as not to be pinched.

Next, the acquisition of a radiation image by the electronic cassette 12 will be described. In the electronic cassette 12 of the present embodiment, a radiation image is taken by the total radiation image capturing apparatus 14 by one irradiation (one shot) of the radiation X. FIG. 6 shows an explanatory diagram for explaining a radiation image taken by each radiation image capturing apparatus 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 radiation image capturing apparatus 14 disposed on the upper side (14 1, _{14 3),} captured radiation image, the radiation that has been taken with a single radiographic image capturing apparatus 14 as shown in FIG. 6 (1) It becomes 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 captured radiation image, a step component will in shadow crowded reflection of the overlapped portion of the upper of the radiographic image capturing apparatus 14 (14 1, _{14 3)} 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 step components are generated due to the step caused by the above. In the following, the component corresponding to the image of the region other than the two types of step components in the radiographic image is referred to as a normal component.

In the present embodiment, the step component caused by the step caused by the scintillator 98 is referred to as a cinch step component, and the step component caused by the step caused by the TFT glass substrate 90 is referred to as a glass step component. When the cinch step component and the glass step component are not distinguished, they are collectively referred to as a step component. Further, an image showing the boundary between the cinch step component and the glass step component is called a cinch step, and an image showing the boundary between the glass step component and the normal component is called a glass step. When the cinch step and the glass step are not distinguished, they are collectively referred to as a step.

Since the thus crowded-through the shadow of the upper radiographic imaging device 14 (14 1, _{14 3),} cinch stepped component, glass stepped component, and the normal component have different concentrations of the corresponding area (image).

FIG. 7 shows 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. 7 (1) 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 are different depending on the incident angle, and the positions of the cinch step and the glass step are different. As shown in FIG. 7 (1), the scintigraphic step and the glass step when the radiation X is irradiated from the position A (see FIG. 5A) and the radiation X when the radiation X is irradiated from the position B (see FIG. 5A). The positions are different between the cinch step and the glass step.

Further, FIG. 7 (2) shows a case where the radiation imaging apparatus 14 moves (moves) as shown in FIG. 5C. When the radiation imaging apparatus 14 moves (moves), the angles of the cinch step component and the glass step component differ depending on the movement (movement), and the cinch step and the glass step become the cinch step and the glass step before the movement. Is non-parallel to. As shown in FIG. 7 (2), the cinch step and glass step when photographed in the state of FIG. 5B (before movement) and the cinch step and glass when photographed in the state of FIG. 5C (after movement). It is not parallel to the step.

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 positions of the cinch step component and the glass step component change. That is, the position shift 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, in the radiographic image capturing system 10 of the present embodiment, correction of the radiographic image captured by each radiographic imaging apparatus 14 of the electronic cassette 12 will be described. The radiation image captured by the radiation image capturing apparatus 14 is subjected to various corrections by image processing.

In the radiographic image capturing system 10 of the present embodiment, the radiographic images taken by each radiographic imaging apparatus 14 of the electronic cassette 12 are output to the console 20 from the control unit 106 of each radiographic imaging apparatus 14. The console 20 functions as each functional unit such as a correction unit that performs image processing including various corrections and correction of misalignment of step components on the radiation image input from each radiation image capturing device 14. The function as the correction unit is not limited to the control unit 30 of the console 20, and may be possessed by other functional units of the console 20, or may be possessed by the electronic cassette 12 or the radiographic image capturing device 14. .. Further, the functional unit for performing the correction may be different 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 radiographic imaging apparatus 14.

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

The method for recognizing whether the radiographic image capturing apparatus 14 that has captured the radiographic image is located on the upper side or the lower side is not limited to the present embodiment. For example, each radiographic image capturing device 14 may add information indicating whether its own device is the upper side or the lower side to the radiographic image and output it to the console 20.

Console 20 in the present embodiment, when performing lower radiographic imaging apparatus 14 (14 ₂₎ radiographic image obtained by imaging a subject 18 (hereinafter, referred to as photographed image) correction for the (level difference correction, described later in detail), Referring to corrected photographic image of the upper of the radiographic image capturing apparatus 14 ₍₁₄ 1, 14 _3). Therefore, first, the correction on the upper side of the radiographic imaging apparatus 14 ₍₁₄ 1, 14 ₃₎ in the images picked up.

Upper radiographic imaging device 14 ₍₁₄ 1, 14 ₃₎ correction for the images picked up will be described. Figure 8 is a flowchart showing an example of the upper radiographic imaging device 14 (14 1, _{14 3)} image processing flow for correcting for image captured by the. In the console 20 of the present embodiment, with respect to the upper of the radiographic image capturing apparatus 14 (14 1, _{14 3)} in the images picked up, offset correction, gain correction, and three types of correction of defect correction performed.

In step S100, the control unit 30 of the console 20 acquires the captured image of the upper radiation image capturing device 14 once stored from the storage unit 50. Specifically, the control unit 30 of the present embodiment acquires the captured image of any _{of the radiographic image capturing devices 14 1} and 14 _3. In the following, as a specific example of the photographed image taken by the radiation image capturing apparatus 14, a photographed image (radiation image) obtained by photographing the subject 18 with the radiation X emitted from the position B (see FIG. 5A) will be described. To do.

In the next step S102, the control unit 30 obtains the acquired photographed image (radiographic image capturing apparatus ₁₄ 1, 14 ₃₎ to the corresponding Geinkyaribu image (described in detail later) from the storage unit 50.

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

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

The gain correction (gain calibration) is to correct the variation in the sensitivity of each pixel 100 on the entire surface of the imaging region of the radiation detector 26. Gain correction is based on a radiation image (hereinafter referred to as a gain caliber image) taken by irradiating the shooting area with radiation X in a state where there is no obstruction in the shooting area or a reference subject is present. , Correct the captured image. The gain components include the intensity distribution of the radiation X emitted from the radiation irradiation device 16, the variation in the sensitivity of each pixel 100 of the radiation detector 26, the variation 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 of the present embodiment acquires a gain caliber image of each radiation image capturing device 14 captured by irradiating radiation X from a position A (see FIG. 5A) in a state where no obstruction exists in the imaging region. Then, it is stored in the storage unit 50 in advance in association with information such as an ID indicating the radiation image capturing device 14. The control unit 30 corrects the gain of the captured image by correcting the variation in the sensitivity of each pixel 100 of the radiation detector 26 based on the gain caliber image stored in the storage unit 50.

In the Geinkyaribu image and the photographed image, but the irradiation position of the radiation X are different, in the upper radiographic imaging device 14 (14 1, _{14 3),} since the stepped component does not occur, performs appropriate gain correction be able to.

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

The captured image obtained by performing 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 performs the correction on image captured by the lower side of the radiographic imaging apparatus 14 (14 _2).

Correction for image captured by the lower side of the radiographic imaging apparatus 14 (14 ₂₎ is described. FIG 9 shows a flow chart showing an example of an image processing flow for correcting for image captured by the lower side of the radiographic imaging apparatus 14 (14 _2).

In the console 20 of the present embodiment, with respect to image captured by the lower side of the radiographic imaging apparatus 14 (14 _2), the aforementioned offset correction, four gain correction, and defect correction in addition to the step correction Is corrected.

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. Further, as a specific example, the position (radiation incident angle) of the radiation irradiation device 16 differs between when the gain caliber image is captured (position A) and when the captured image is captured (position B), and is shown in FIG. 5C. A case where the radiation image capturing apparatus 14 moves (moves) will be described.

Figure 10 is a schematic view for explaining an example of an image processing flow for correcting for image captured by the lower side of the radiographic imaging apparatus 14 (14 _2).

The control unit 30 of the console 20 detects the positions of the cinch step component and the glass step component from the gain caliber image in advance before performing the image processing shown in FIG. The method of detecting the positions of the cinch step component and the glass step component from the gain caliber 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 caliber image after performing the noise removing process. There is. As the processing for removing noise, for example, a main direction median filter processing is performed as a high frequency removal processing. The main direction is a direction that intersects with the sub direction of the electronic cassette 12. The sub-direction is the direction in which the radiation irradiation device 16 moves, and is the long direction of the electronic cassette 12 in the present embodiment. Further, for example, a moving average filtering process may be applied, or another high frequency removing filter may be applied.

As a method of detecting the positions of the cinch step component and the glass step component in the gain caliber image after the noise removal process, for example, by detecting a straight line (an image representing a straight line) from the gain caliber image. , The cinch step and the glass step may be detected, and the positions of the cinch step component and the glass step component may be detected based on the detected cinch step and the glass step. The method for detecting a straight line is not particularly limited, and a general method may be used. For example, a Hough transform or the like may be used.

In step S200 of image processing, similarly to step S100 described above, the control unit 30 of the console 20 acquires the captured image of the lower radiation image capturing device 14 once 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, similarly to step S102 described above, the control unit 30 obtains the Geinkyaribu image corresponding to the acquired photographed image (radiographic image capturing apparatus 14 ₂₎ from the storage unit 50.

In the console 20 of the present embodiment, in order to make it easier to detect the position of the step from the captured image, offset correction and defect correction are performed before detecting the position of the step. Therefore, in the next step S204, the control unit 30 performs offset correction of the captured image in the same manner as in step S104 described above.

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 caliber image (gain caliber image in which nothing is corrected) acquired in step S202.

The gain correction and defect correction methods are not particularly limited. Since the acquired captured image and the gain caliber 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 the gain correction performed by the control unit 30 of the present embodiment will be described, but the gain correction method is not particularly limited. Since the gain correction corrects the variation in sensitivity for each pixel, it is not preferable that the irradiation field is narrowed down 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 may be too large or too small in order to detect the irradiation field diaphragm or to detect the attenuation of the radiation X due to the excessive heel effect. If it is, it is judged as an error. Since the QL value drops significantly in the step component portion, error determination is performed in consideration of this. Since the pixel value drops significantly in the step component portion where the radiation imaging apparatus 14 overlaps, the ratio of the pixel value between the overlapping area and the non-overlapping area 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 values, it is possible to eliminate the influence of radiation absorption in the overlapping region and determine the abnormality of the pixel value. After determining the abnormality of the pixel value in this way, the gain of the offset-corrected captured image is corrected based on the gain-calibrated image.

As described above, the position of the radiation irradiation device 16 (incident angle of radiation) at the time of photographing is different between the gain caliber image and the photographed image. In addition, the radiation imaging device 14 is moving (moving). Therefore, as described above, the position of the step component generated in the gain caliber image and the position of the step component generated in the captured image are different. Since the position of the step component is different between the gain caliber image and the captured image, when the gain correction is performed, the step component of the gain caliber image and the step component of the captured image and the two step components are generated in the corrected image. .. Since the step component of the present embodiment includes the cinch step component and the glass step component, four steps occur in the image after gain correction (see FIGS. 10 and 7 (2)).

Further, a specific example of defect correction performed by the control unit 30 of the present embodiment will be described, but the method of defect correction is not particularly limited. In the control unit 30 of the present embodiment, the captured image that has been offset-corrected is subjected to ambient statistical processing by processing with a median filter in the main direction and the sub direction, a moving average filter, a high frequency filter, and the like. Defect correction is performed by an algorithm that determines the difference between the captured image and the captured image before processing as a threshold. The threshold value is compared for each pixel 100, and it is determined whether or not the pixel is a defective pixel based on the threshold value. As the threshold value, the ratio of the pixel value as a result of performing statistical processing of the surroundings by applying a median filter to the pixel value of the normal component is taken, and the value obtained by 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 coefficient of the reciprocal. In the present embodiment, the reciprocal gain correction is performed as a specific example of the coefficient of the reciprocal. As described above, the captured image to be subjected to the reverse gain correction in this step has four steps.

The control unit 30 of the present embodiment performs reverse gain correction based on a gain caliber image for reverse gain correction acquired in advance. As the gain caliber image for reverse gain correction, a gain caliber image in which noise such as high frequency noise is removed by high frequency removal processing is acquired in advance. The method for removing noise is not particularly limited, and for example, a median filter process having a mask size capable of removing point defects and line defects may be applied in the main direction and the sub direction, or a moving average filter process may be applied. Alternatively, other high frequency rejection filters may be applied.

After that, in the control unit 30 of the present embodiment, as a specific example, the step component (the step component due to the absorption of radiation X by the scintillator 98 and the radiation X by the TFT glass substrate 90) is obtained with respect to the gain caliber image from which noise has been removed. Cut out the step component due to absorption). Actually, the position of the step component is not known exactly, but since the area where the step component occurs can be obtained by design or experiment, by trimming the area including all the obtained areas. 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 caliber 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 caliber image for reverse gain correction. .. The control unit 30 multiplies the gain caliber image for reverse gain correction acquired in advance by the captured image whose defects have been corrected by the process of step S206 to perform reverse gain correction.

The position of the step component of the gain caliber image used for the reverse gain correction is different from that of the captured image, but is the same as that of the gain caliber image used for the gain correction in step S206. Therefore, by performing the reverse gain correction, the step component caused by the gain caliber image is removed, so that the four steps generated in the captured image are returned to the two steps.

Further, by performing the reverse gain correction, the captured image becomes the same as the image before the gain correction for 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 method of detecting the positions 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 cinch step and a glass step by detecting a straight line (an image representing a straight line) from the captured image, and based on the detected cinch step and the glass step. , Cinch step component and glass step component are detected. The method for detecting a straight line is not particularly limited, and a general method may be used. For example, a Hough transform or the like may be used.

When detecting a straight line from the captured image, a process of detecting the 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 estimated position is included in the region. 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 may 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 amount of misalignment of the cinch step component and the glass step component is obtained by design or experiment, and is based on the cinch step, glass step, and misalignment amount detected in advance from the gain caliber image. It may be assumed that there is a cinch step and a glass step within the range. As described above, it is possible to improve the detection accuracy by performing the process of detecting the straight line in the region including the estimated position as compared with the case of performing the process of detecting the straight line in the entire captured image.

Since the difference in the transmittance of radiation X is smaller in the glass step than in the cinch step, the difference in concentration between the glass step component and the normal component is small. 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, by converting the coordinates of the gain caliber image after the defect correction, the position of the step component of the gain caliber image is corrected so as to match the position of the step component of the captured image detected in step S210. In the present embodiment, the coordinates of the image are the coordinates (positions) of the pixels, the y direction is the long direction (secondary direction) in which the irradiation device 16 moves, and the x direction intersects the long direction. The direction (main direction) to do. The method of converting the coordinates is not limited, and examples thereof include a method of translating the step component of the gain caliber image, a method of rotating the coordinate, and a method of deforming the shape of the step component. As a specific example of the method of deforming the shape of the step component, the step component of the gain caliber image is deformed into a parallel quadrilateral shape in the subdirection according to the angular deviation between the detected step of the gain caliber image and the step of the captured image. (See FIG. 10). When the shape is transformed into a parallel quadrilateral shape in this way, it is not necessary to consider the image information of the region protruding from the rectangle when applied to the gain caliber image of the rectangle.

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 device 14 _3. Therefore, the control unit 30 converts the coordinates of both step components of the gain caliber image to correct the position of the step component. If a 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 caliber image for gain correction, it is preferable to perform a process in which the image between the two step components (corresponding to the normal component) and each step component that have undergone coordinate conversion are smoothly connected.

In the next step S214, the control unit 30 performs gain correction of the captured image obtained by reverse gain correction in step S208 based on the gain caliber image in which the position of the step component is corrected by the processing of step S212.

In the gain correction in this step, since the position of the step component of the gain caliber image is aligned with the position of the step component of the captured image, the step component does not become four as in the gain correction performed in step S206. Gain correction can be performed appropriately.

Further, in the console 20 of the present embodiment, the step component generated in the captured image is corrected (step correction). In the present embodiment, the step correction means a correction for reducing the density difference between the concentration of the step component and the concentration of the normal component. By performing the offset correction, the gain correction, and the defective pixel correction in advance, the step correction can be appropriately performed.

Therefore, in the next step S216, the control unit 30 first corrects the step difference 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 (the y coordinate is constant) but diagonal, the step is in the x range where the y coordinate is constant, for example, referring to the technique described in JP-A-2009-285354. Make corrections. Since vertical streaks occur at the x-range boundary where the y-coordinate changes, smoothing the corrected image (calculated by smoothing the difference between the pixel values of the adjacent y-coordinates of the boundary in the main direction) in the x-direction causes vertical streaks. It is possible to prevent the occurrence of streaks.

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

In the next step S218, the control unit 30 corrects the step of the cinch step component. A specific example of 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 divides the cinch step component into two regions and corrects the step.

On the photographed image, for areas where the image information to the captured image of the upper of the radiographic image capturing apparatus 14 ₍₁₄ 1, 14 ₃₎ are present (overlapping region), the upper radiographic imaging device 14 ₍₁₄ 1, 14 ₃ ) Image information is diverted. Therefore, in this embodiment, it is performed first correction for the captured image of the upper of the radiographic image capturing apparatus 14 (14 1, _{14 3).} 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, the inside of each radiation imaging device 14, and the radiation imaging device 14 are obtained. It may be stored in a control unit, a storage unit (not shown), or the like in the electronic cassette 12.

Further, as shown in FIG. 5A, the upper radiographic imaging device 14 ₍₁₄ 1, 14 _3), than the lower of the radiographic image capturing apparatus 14 (14 _2), because the SID is different, the upper diverting It is preferable to match the magnification of the captured image with the captured image on the lower side. As for the magnification, the set value or the value obtained by an experiment or the like is obtained in advance as in the area of the image information to be diverted, and the storage unit 50 of the console 20, each radiation imaging device 14, and the electronic cassette 12 are used. It may be stored in a control unit, a storage unit (not shown), or the like.

Further, in the region other than the overlap region, the correction amount is calculated so as to smoothly connect the overlap region and the cinch step, 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 present image processing. The captured image after this processing (after step correction) is stored in the storage unit 50.

In addition, the portion that was the step component may be an image that has a sense of discomfort with respect to the normal component portion. For example, the graininess of the image may differ between the portion that was the step component and the normal component portion. Therefore, it is preferable to perform various processes on the captured image after this process in order to further improve the image quality.

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

Or the electronic cassette 12 of the present embodiment as described is provided with three radiographic imaging device 14 ₍₁₄ 1 to 14 _3). Radiographic imaging apparatus 14 _1, 14 ₃ are the upper side (the side close to the radiation irradiation device 16), the radiation image capturing apparatus 14 ₂ is arranged in a so-called terrace shape having a (the side far from the radiation irradiation device 16) lower.

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

Control unit 30, based on Geinkyaribu image which has been stored in the storage unit 50 performs gain correction of the captured image of the upper of the radiographic image capturing apparatus 14 (14 1, _{14 3).}

On the other hand, the photographic image of the lower radiographic imaging apparatus 14 (14 ₂₎ is due to the stepped end of the upper radiographic imaging device 14 ₍₁₄ 1, 14 ₃₎ scintillator 98 and the TFT glass substrate 90 of the A step component (cinch step component and glass step component) is 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 caliber 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 caliber image according to the positions of the cinch step component and the glass step component of the captured image. To do. The control unit 30 corrects the gain of the captured image based on the corrected gain caliber image.

In the present embodiment, the positions of the cinch step component and the glass step component change according to the position of the radiation irradiation device 16 (incident angle of radiation) and the movement (movement) of the radiation imaging device 14. The positions of the cinch step and the glass step move substantially in parallel in the elongated direction according to the position of the radiation irradiation device 16 (incident angle of radiation). Further, the angles of the cinch step and the glass step change according to the movement (movement) of the radiation imaging apparatus 14. Therefore, the positions of the cinch step component and the glass step component may differ between the gain caliber image and the captured image. When the gain correction of the captured image is performed using the gain caliber images in which the positions of the step components are different, four steps are generated in the captured image after the gain correction due to the two step components.

On the other hand, the control unit 30 of the present embodiment corrects the positions of the cinch step component and the glass step component of the gain caliber image according to the positions of the cinch step component and the glass step component of the photographed image. Since the gain correction of the captured image is performed based on the corrected gain caliber image, the gain correction of the captured image can be appropriately performed. Further, 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 radiation image capturing system 10 (console 20) of the present embodiment, even when the incident direction of radiation changes between the gain caliber image and the captured image, it is appropriate to correct the step component generated in the captured image. Can be done.

If the positions of the cinch step component and the glass step component of the gain caliber image detected in advance match the positions of the cinch step component and the glass step component of the captured image detected in step S210, step S212 The process may be omitted. When the positions of the cinch step component and the glass step component of the gain caliber image and the captured image match in this way, even if the gain correction of the captured image is performed based on the gain caliber image, the number of steps becomes four as described above. Never. Therefore, the gain correction of the captured image can be appropriately performed based on the gain caliber image.

Further, in the present embodiment, since the end portion of the scintillator 98 and the end portion of the TFT glass substrate 90 are different, a case where a step is generated (two steps are generated) due to each is described, but the number of steps is described. 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, not only the gain caliber image but also other correction images, the position of the radiation irradiation device 16 (irradiation position of radiation X) differs between when the correction image is taken and when the shot image is taken. Needless to say, the present invention can be applied to cases.

Further, the gain correction in step S206 and the reverse gain correction in step S208 may be omitted, and only the defect correction may be performed. 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 of correcting the positional deviation of the step component, the position of the step component of the gain caliber image is aligned with the position of the step component of the captured image by converting the coordinates of the gain caliber image. It has been corrected, but the correction method is not limited. For example, instead of the gain caliber image, the coordinates of the captured image may be converted. Further, the coordinates of both the gain caliber image and the captured image may be converted. When the coordinates of the captured image are converted, it is preferable to restore the coordinates (reverse transformation) after the gain correction of the captured image.

Further, in the present embodiment, the case where the electronic cassette 12 includes three radiographic imaging devices 14 has been described, but the number of radiographic imaging devices 14 is not particularly limited. Further, the method of superimposing the radiation imaging 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 radiation 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. 11 and 12 show specific configuration examples when a plurality of electronic cassettes are arranged adjacent to each other. _{11 and 12 show a case where three} electronic cassettes 62 (62 _{1 to} 623) are arranged adjacent to each other. Further, FIG. 11 shows a case where the electronic cassette 12 is arranged in a terrace shape, similarly to the radiation imaging device 14 of the electronic cassette 12 of the present embodiment. FIG. 12 shows a case where the electronic cassette 12 is arranged in a staircase pattern.

Further, in each of the above embodiments, the case where the present invention is applied to the radiation detector 26 of the indirect conversion method that converts the converted light into electric charges has been described, but the present invention is not limited thereto. 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 electric charge as a photoelectric conversion layer that absorbs radiation and converts it into electric charge.

In addition, the configuration, operation, and the like of the radiation imaging system 10, the electronic cassette 12, the radiation imaging device 14, the console 20, and the like described in the present embodiment are examples, and the situation is within a range that does not deviate from the gist of the present invention. Needless to say, it can be changed according to the situation.

Further, in the present embodiment, the radiation of the present invention is not particularly limited, and X-rays, γ-rays and the like can be applied.

10 Radiation imaging system 12, 62 Electronic cassette 14, 14 _{1 to} 14 ₃ Radiation imaging device 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 (6)

A first substrate in which a first conversion layer that converts radiation incident from a radiation irradiation device into light and a plurality of first pixels that accumulate charges generated in response to the light converted by the first conversion layer are formed. A first radiation imaging device that captures a first radiation image equipped with
A second conversion layer that is arranged on a side farther from the radiation irradiation device than the first radiation imaging device in a state in which a part of the radiation is overlapped with respect to the incident direction of the radiation and converts the radiation into light. A second radiation imaging apparatus that includes a second substrate on which a plurality of second pixels that store charges generated in response to the light converted by the second conversion layer are formed, and captures a second radiation image.
The first radiation image and the second radiation image are acquired, and the conversion layer step indicated by the conversion layer step component caused by the first conversion layer of the first radiation imaging apparatus with respect to the second radiation image. of, for the overlap area where the image information to the first radiographic image exists, the conversion layer step to be low reduction corrected by diverting an image of an area corresponding to the overlap region of the first radiation image In addition, the substrate step indicated by the substrate step component caused by the first substrate of the first radiation imaging apparatus is the concentration of the substrate step component, the conversion layer step component in the second radiation image, and the substrate step component. A correction unit that performs correction by reducing the density difference from the density of the normal component corresponding to the image of the region other than the substrate step component, and the correction unit.
Radiation imaging system equipped with. The correction unit derives and derives a correction amount for smoothly connecting the diverted first radiation image and the conversion layer step in a region different from the overlap region among the conversion layer step components. Make corrections according to the amount of correction,
The radiographic imaging system according to claim 1. The correction unit corrects the substrate step, and then corrects the conversion layer step.
The radiographic imaging system according to claim 1 or 2. A first substrate on which a first conversion layer that converts radiation incident from a radiation irradiation device into light and a plurality of first pixels that accumulate charges generated in response to the light converted by the first conversion layer are formed. A part of the first radiation image taken by the first radiation imaging apparatus provided with and is superimposed on the side farther from the radiation irradiation apparatus than the first radiation imaging apparatus with respect to the incident direction of the radiation. A second conversion layer for converting the radiation into light and a plurality of second pixels for accumulating charges generated in response to the light converted by the second conversion layer are formed. A second radiation image taken by a second radiation imaging apparatus provided with a substrate is acquired, and the second radiation image is generated due to the first conversion layer of the first radiation imaging apparatus. Among the conversion layer steps indicated by the conversion layer step component, for the overlap region in which the image information exists in the first radiation image, the image of the region corresponding to the overlap region of the first radiation image is diverted to the above. Correction is performed to reduce the conversion layer step, and the substrate step indicated by the substrate step component caused by the first substrate of the first radiation imaging apparatus is the concentration of the substrate step component and the second radiation. An image processing apparatus including a correction unit that performs correction by reducing a density difference from the density of a normal component corresponding to an image in a region other than the conversion layer step component and the substrate step component in an image. A first substrate on which a first conversion layer that converts radiation incident from a radiation irradiation device into light and a plurality of first pixels that accumulate charges generated in response to the light converted by the first conversion layer are formed. A part of the first radiation imaging device for capturing a first radiation image and a side farther from the radiation irradiation device than the first radiation imaging device with respect to the incident direction of the radiation is superposed. A second substrate in which a second conversion layer that converts the radiation into light and a plurality of second pixels that accumulate charges generated in response to the light converted by the second conversion layer are formed. It is a control method of a radiation imaging system including a second radiation imaging apparatus for capturing a second radiation image, and a radiation imaging system.
The step of acquiring the first radiation image and the second radiation image, and
With respect to the second radiation image, image information exists in the first radiation image among the conversion layer steps indicated by the conversion layer step component caused by the first conversion layer of the first radiation image capturing apparatus. for the overlap region, performs a correction for low reducing the conversion layer step by diverting an image of the area corresponding to the overlap region of the first radiation image, also, the first of the first radiographic image capturing apparatus The substrate step indicated by the substrate step component caused by one substrate corresponds to the concentration of the substrate step component and the image of the region other than the conversion layer step component and the substrate step component in the second radiation image. A step of making corrections by reducing the concentration difference from the concentration of normal components, and
A method of controlling a radiographic imaging system equipped with. A control program for a radiographic imaging system for causing a computer to execute each step of the method for controlling a radiographic imaging system according to claim 5.

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