JP5566861B2 - Portable radiography system - Google Patents

Description

  The present invention relates to a portable radiographic apparatus that captures a radiographic image indicated by irradiated radiation.

  In recent years, a radiation sensitive layer is disposed on a TFT (Thin Film Transistor) active matrix substrate, radiation such as irradiated X-rays is detected, and an electric signal indicating a radiation image represented by the detected radiation is output (FPD). Radiation detectors such as Flat Panel Detector have been put into practical use. This radiation detector has an advantage that an image can be confirmed immediately and a moving image can be confirmed as compared with a conventional imaging plate. Radiation detectors convert radiation into indirect conversion methods in which radiation is converted into light by a scintillator and then converted into charges in a semiconductor layer such as a photodiode, or radiation is charged in a semiconductor layer such as amorphous selenium. There are various types of materials that can be used for the semiconductor layer in each method.

  A portable radiation imaging apparatus (hereinafter also referred to as an electronic cassette) that incorporates this radiation detector and stores radiation image data output from the radiation detector has been put into practical use. In surgery, it is important to be able to display a radiation image immediately after imaging in order to perform a quick and accurate treatment on a patient. The electronic cassette can quickly confirm the image and satisfy this demand.

  As a technique related to this radiation detector, Patent Document 1 discloses radiation including a photoelectric conversion unit that can receive light from both front and back surfaces, and first and second scintillators that convert radiation into fluorescence that can be detected by the photoelectric conversion unit. In the detector, a radiation detector is described in which a photoelectric conversion unit is integrally formed on the first scintillator, and a first scintillator, a photoelectric conversion unit, and a second scintillator are sequentially stacked. According to the technique of this Patent Document 1, X-rays are incident from the scintillator side when the photographing is performed, the scintillator emits light, and the phosphor glass emits light by the X-rays transmitted through the scintillator. Sensitivity can be increased by receiving both light generated by the scintillator.

  Patent Document 2 discloses that two scintillators that convert irradiated radiation into visible light, and visible light that is arranged between the two scintillators and converted by the scintillator are converted into electrical signals. There is disclosed a solid-state photodetector in which a large number of output solid-state photodetector elements are formed on a substrate. According to the technique of this Patent Document 2, since the solid-state photodetector is arranged between the two scintillators, the first radiation arranged on the radiation irradiation side by the radiation irradiated to the radiation detector. Since the scintillator emits light and other scintillators after being arranged on the opposite side emit light, the detection efficiency of visible light in the solid-state photodetector is improved.

JP-A-9-145845 Japanese Patent Laid-Open No. 7-27865

  By the way, in surgery, switching between a moving image and a still image is important, or when a still image is taken, a higher quality image may be required.

  Although electronic cassettes can shoot moving images and still images, the sensitivity and image quality differ depending on the configuration of the built-in radiation detector, and the configuration suitable for shooting also differs between moving images and still images. Although it is possible to improve the image quality by increasing the amount, there is a limit to the improvement of the image quality and the exposure dose of the patient increases.

  For this reason, in order to capture radiographic images having different characteristics, it is necessary to prepare a plurality of electronic cassettes incorporating radiation detectors having different characteristics.

  Note that the techniques of Patent Document 1 and Patent Document 2 are not related to radiographic imaging with different characteristics.

  In view of the above circumstances, an object of the present invention is to provide a portable radiation imaging apparatus that can easily capture radiation images having different characteristics.

In order to achieve the above object, the portable radiographic imaging device according to claim 1 is formed in a flat plate shape, and when the radiation is irradiated to one surface side of the flat plate shape and Ri Do the different characteristics of the radiation image to be photographed in the case that radiation on the other surface is irradiated, the light emitting layer where light is generated by radiation is irradiated, and to receive the light generated in the light-emitting layer A radiation detector constructed by laminating a substrate on which a charge element is accumulated and a switch element for reading out the charge is stacked is built-in, and irradiation is performed on both the one surface side and the other surface side. It is possible to take a radiographic image of the emitted radiation.

The portable radiographic imaging device of the present invention is formed in a flat plate shape, and when radiation is applied to one side of the flat plate and when the other surface side of the flat plate is irradiated with radiation. in characteristics of captured the radiation image Ri is Do different, the light emitting layer where light is generated by radiation is irradiated, and for reading the charge together with the charges are accumulated by receiving light generated in the light-emitting layer A radiation detector constructed by laminating a substrate on which the switch element is formed is incorporated.

  The portable radiographic apparatus of the present invention can capture a radiographic image of the irradiated radiation on either one side or the other side.

As described above, the portable radiographic imaging device of the present invention has characteristics of radiographic images captured when radiation is applied to one side and when the other side of the flat plate is irradiated. substrate but depends, emitting layer where light is generated by radiation is irradiated, and switching elements for reading the charges are formed along with the charge is accumulated by receiving light generated in the light-emitting layer Since the radiation image by the irradiated radiation can be taken on either the one surface side or the other surface side of the radiation detector constructed by stacking the radiation detectors, radiation images having different characteristics can be easily taken.

According to the present invention, as in the invention described in claim 2 , the radiation detector is provided with either one of the light emitting layer and the substrate, and the light emitting layer and the substrate are alternately stacked. It is good also as the structure made to do.

The present invention, as in the invention according to claim 3, wherein the radiation detector, together with the substrate and the light emitting layer is provided two each, shielding plates are provided for shielding the radiation, the shield plate The light emitting layer and the substrate may be laminated on the one surface side and the other surface side.

The invention according to claim 2 or claim 3, as in the invention according to claim 4, wherein the radiation detector, the light-emitting layer has two provided Rutotomoni, the two thicknesses of the light-emitting layer The particle size of the particles that are filled in the light emitting layer and emit light when irradiated with radiation, the multilayer structure of the particles, the filling rate of the particles, the doping amount of the activator, the material of the light emitting layer, and the light emission At least one of the layer structures of the layers may be changed, and a reflective layer that reflects the light may be formed on a surface of the light emitting layer that is not opposed to the substrate.

Further, the invention according to claim 2 or claim 3, as in the invention of claim 5, wherein the radiation detector, wherein the substrate is two provided Rutotomoni, reading of the two substrates of the signal Changes in characteristics may be made.

Further, according to the present invention, as in the invention described in claim 6 , the radiation detector has a direct conversion in which either one of the one surface side and the other surface side converts radiation into electric charge in a semiconductor layer. The system may be a system, and the other may be an indirect conversion system in which radiation is converted into light and then converted into electric charge.

Further, in the present invention, as in the invention described in claim 7 , the light emitting layer may include a columnar crystal of a phosphor material that emits light when irradiated with radiation.

In the invention described in claim 7 , as in the invention described in claim 8 , the phosphor material may be CsI.

The present invention, as in the invention according to claim 9, wherein the radiation detector is one of the one surface side and the other surface side is a characteristic of the image-quality priority, the other is the sensitivity emphasis May be the characteristic.

In addition, the invention according to any one of claims 1 to 9 is formed in a flat plate shape as in the invention according to claim 10, and the radiation detector is built in, and the flat plate shape. An imaging unit capable of capturing a radiographic image of the irradiated radiation on either the one surface side or the other surface side, a control unit incorporating a control unit for controlling the imaging operation of the radiation detector, There may be provided a connecting member that can be opened and closed in an unfolded state in which the photographing unit and the control unit are arranged, and a storage state in which the photographing unit and the control unit are overlapped and folded.

In addition, the invention according to any one of claims 1 to 9 is formed in a flat plate shape as in the invention according to claim 11, and the radiation detector is built in the flat plate shape. An imaging unit capable of capturing a radiographic image of the irradiated radiation on either the one surface side or the other surface side, a control unit incorporating a control unit for controlling the imaging operation of the radiation detector, And a connecting member that reversibly connects one surface of the photographing unit and the other surface to the control unit.

  The radiographic apparatus of the present invention has an excellent effect that radiographic images having different characteristics can be easily captured.

It is sectional drawing which showed typically the structure of the radiation detector which concerns on 1st Embodiment. It is the top view which showed the structure of the radiation detector which concerns on 1st Embodiment. It is sectional drawing which showed roughly the structure of the TFT substrate which concerns on embodiment. It is sectional drawing which showed the structure of the radiation detector which concerns on 1st Embodiment. It is a graph which shows the change of the thickness and sensitivity of a scintillator layer concerning an embodiment. It is a graph which shows the change of the thickness of a scintillator layer and image quality concerning an embodiment. It is a perspective view which shows the structure of the flat electronic cassette which concerns on embodiment. It is sectional drawing which shows the structure of the flat electronic cassette which concerns on embodiment. It is a block diagram which shows the principal part structure of the electric system of the electronic cassette concerning 1st and 2nd embodiment. It is a perspective view which shows the structure of the electronic cassette which can be opened and closed which concerns on embodiment. It is a perspective view which shows the structure of the electronic cassette which can be opened and closed which concerns on embodiment. It is sectional drawing which shows the structure of the electronic cassette which can be opened and closed which concerns on embodiment. It is a perspective view which shows the structure of the electronic cassette which can be reversed which concerns on embodiment. It is a perspective view which shows the structure of the electronic cassette which can be reversed which concerns on embodiment. It is sectional drawing which shows the structure of the electronic cassette which can be reversed which concerns on embodiment. It is sectional drawing which showed the structure of the radiation detector which concerns on 2nd Embodiment. It is the schematic diagram which showed the multilayer structure of the small particle and large particle of a scintillator layer. It is sectional drawing which shows a structure at the time of forming a reflection layer in the surface on the opposite side to the TFT substrate of a scintillator layer. It is sectional drawing which showed the structure of the radiation detector which concerns on 3rd Embodiment. It is a block diagram which shows the principal part structure of the electric system of the electronic cassette concerning 3rd and 4th embodiment. It is sectional drawing which showed the structure of the radiation detector which concerns on 4th Embodiment. It is sectional drawing which showed typically the structure of the radiation detector of the direct conversion system which concerns on another form. It is a graph which shows the relationship between the cumulative exposure amount of CsI, and a sensitivity. (A) is sectional drawing which shows the cross-sectional structure in the accommodation state of the electronic cassette which can be opened and closed which concerns on another form, (B) is the cross-sectional structure in the expansion | deployment state of the electronic cassette which can be opened and closed which concerns on another form It is sectional drawing shown. It is a graph which shows an example of the sensitivity change of the scintillator layer formed with CsI.

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

[First Embodiment]
First, the configuration of the radiation detector 20 according to the present embodiment will be described.

  FIG. 1 is a cross-sectional view schematically showing the configuration of the radiation detector 20 according to the present embodiment, and FIG. 2 is a plan view showing the configuration of the radiation detector 20. .

  As shown in FIG. 1, the radiation detector 20 includes a TFT substrate 26 in which a switch element 24 such as a thin film transistor (TFT) is formed on an insulating substrate 22.

  On the TFT substrate 26, a scintillator layer 28 that converts incident radiation into light is formed as an example of a radiation conversion layer that converts incident radiation.

As the scintillator layer 28, for example, CsI: Tl, GOS (Gd ₂ O ₂ S: Tb) can be used. The scintillator layer 28 is not limited to these materials.

  The wavelength range of light emitted by the scintillator layer 28 is preferably a visible light range (wavelength 360 nm to 830 nm), and in order to enable monochrome imaging by the radiation detector 20, a green wavelength range is included. It is more preferable.

  Specifically, the phosphor used in the scintillator layer 28 preferably contains cesium iodide (CsI) when imaging using X-rays as radiation, and the emission spectrum upon irradiation with X-rays is 420 nm to 600 nm. It is particularly preferred to use some CsI (Tl). Note that the emission peak wavelength of CsI (Tl) in the visible light region is 565 nm.

  The scintillator layer 28 may be formed by vapor deposition on a vapor deposition substrate, for example, when it is intended to be formed of columnar crystals such as CsI (Tl). Thus, when the scintillator layer 28 is formed by vapor deposition, an Al plate is often used as the vapor deposition substrate from the viewpoint of X-ray transmittance and cost, but is not limited thereto. When GOS is used as the scintillator layer 28, the scintillator layer 28 may be formed by applying GOS to the surface of the TFT substrate 26 without using a vapor deposition substrate.

As the insulating substrate 22, as long as and absorption of radiation having a light transmitting property is small either well, for example, may be a glass substrate, a transparent ceramic substrate, a light transmissive resin substrate. The insulating substrate 22 is not limited to these materials.

  Between the scintillator layer 28 and the TFT substrate 26, a photoconductive layer 30 that generates charges when light converted by the scintillator layer 28 is incident is disposed. A bias electrode 32 for applying a bias voltage to the photoconductive layer 30 is formed on the surface of the photoconductive layer 30 on the scintillator layer 28 side.

  The photoconductive layer 30 absorbs light emitted from the scintillator layer 28 and generates a charge corresponding to the absorbed light. The photoconductive layer 30 may be formed of a material that generates charges when irradiated with light. For example, the photoconductive layer 30 may be formed of amorphous silicon, an organic photoelectric conversion material, or the like. The photoconductive layer 30 containing amorphous silicon has a wide absorption spectrum and can absorb light emitted by the scintillator layer 28. If the photoconductive layer 30 includes an organic photoelectric conversion material, it has a sharp absorption spectrum in the visible region, and electromagnetic waves other than light emitted by the scintillator layer 28 are hardly absorbed by the photoconductive layer 30, such as X-rays. Noise generated when radiation is absorbed by the photoconductive layer 30 can be effectively suppressed.

  The organic photoelectric conversion material constituting the photoconductive layer 30 is preferably such that its absorption peak wavelength is closer to the emission peak wavelength of the scintillator layer 28 in order to absorb light emitted by the scintillator layer 28 most efficiently. Ideally, the absorption peak wavelength of the organic photoelectric conversion material matches the emission peak wavelength of the scintillator layer 28, but if the difference between the two is small, the light emitted from the scintillator layer 28 can be sufficiently absorbed. It is. Specifically, the difference between the absorption peak wavelength of the organic photoelectric conversion material and the emission peak wavelength with respect to the radiation of the scintillator layer 28 is preferably within 10 nm, and more preferably within 5 nm.

  Examples of organic photoelectric conversion materials that can satisfy such conditions include quinacridone-based organic compounds and phthalocyanine-based organic compounds. For example, since the absorption peak wavelength of quinacridone in the visible region is 560 nm, if quinacridone is used as the organic photoelectric conversion material and CsI (Tl) is used as the material of the scintillator layer 28, the difference in the peak wavelength may be within 5 nm. The amount of charge generated in the photoconductive layer 30 can be substantially maximized.

  On the TFT substrate 26, a charge collecting electrode 34 for collecting charges generated in the photoconductive layer 30 is formed. In the TFT substrate 26, the charges collected by the charge collection electrodes 34 are read out by the switch element 24.

  Next, the photoconductive layer 30 applicable to the radiation detector 20 according to the present embodiment will be specifically described.

  The electromagnetic wave absorption / photoelectric conversion site in the radiation detector 20 according to the present invention includes a pair of charge collection electrode 34 and bias electrode 32, and a photoconductive layer 30 sandwiched between the charge collection electrode 34 and bias electrode 32. It can be comprised by the organic layer to contain. More specifically, this organic layer is a part that absorbs electromagnetic waves, a photoelectric conversion part, an electron transport part, a hole transport part, an electron blocking part, a hole blocking part, a crystallization preventing part, an electrode, and an interlayer contact improvement. It can be formed by stacking or mixing parts.

  The organic layer preferably contains an organic p-type compound or an organic n-type compound.

  The organic p-type semiconductor (compound) is a donor organic semiconductor (compound) mainly represented by a hole-transporting organic compound and refers to an organic compound having a property of easily donating electrons. More specifically, an organic compound having a smaller ionization potential when two organic materials are used in contact with each other. Therefore, any organic compound can be used as the donor organic compound as long as it is an electron-donating organic compound.

  An organic n-type semiconductor (compound) is an acceptor organic semiconductor (compound) mainly represented by an electron-transporting organic compound and refers to an organic compound having a property of easily accepting electrons. More specifically, the organic compound having the higher electron affinity when two organic compounds are used in contact with each other. Therefore, as the acceptor organic compound, any organic compound can be used as long as it is an electron-accepting organic compound.

  Since the materials applicable as the organic p-type semiconductor and organic n-type semiconductor and the configuration of the photoconductive layer 30 are described in detail in Japanese Patent Application Laid-Open No. 2009-32854, description thereof is omitted. The photoconductive layer 30 may be formed by further containing fullerenes or carbon nanotubes.

  The sensor unit 36 constituting each pixel unit only needs to include at least the charge collection electrode 34, the photoconductive layer 30, and the bias electrode 32. In order to suppress an increase in dark current, an electron blocking film and a hole blocking unit are included. It is preferable to provide at least one of the films, and it is more preferable to provide both.

  The electron blocking film can be provided between the charge collection electrode 34 and the photoconductive layer 30, and when a bias voltage is applied between the charge collection electrode 34 and the bias electrode 32, the charge collection electrode 34 to the photoconductive layer 30. It is possible to prevent the dark current from being increased due to the injection of electrons.

  An electron donating organic material can be used for the electron blocking film.

  The material actually used for the electron blocking film may be selected according to the material of the adjacent electrode, the material of the adjacent photoconductive layer 30 and the like, and the electron function is 1.3 eV or more from the work function (Wf) of the adjacent electrode material. Those having a large affinity (Ea) and an Ip equivalent to or smaller than the ionization potential (Ip) of the material of the adjacent photoconductive layer 30 are preferable. Since the material applicable as the electron donating organic material is described in detail in Japanese Patent Application Laid-Open No. 2009-32854, description thereof is omitted.

  The thickness of the electron blocking film is preferably 10 nm or more and 200 nm or less, more preferably 30 nm or more and 150 nm or less, and particularly preferably 50 nm, in order to surely exhibit the dark current suppressing effect and prevent a decrease in the photoelectric conversion efficiency of the sensor unit 36. It is 100 nm or less.

  The hole blocking film can be provided between the photoconductive layer 30 and the bias electrode 32. When a bias voltage is applied between the charge collecting electrode 34 and the bias electrode 32, the hole blocking film is applied from the bias electrode 32 to the photoconductive layer 30. It is possible to suppress the increase in dark current due to the injection of holes.

  An electron-accepting organic material can be used for the hole blocking film.

  The thickness of the hole blocking film is preferably 10 nm or more and 200 nm or less, more preferably 30 nm or more and 150 nm or less, particularly preferably, in order to surely exhibit the dark current suppressing effect and prevent a decrease in photoelectric conversion efficiency of the sensor unit 36. It is 50 nm or more and 100 nm or less.

  The material actually used for the hole blocking film may be selected according to the material of the adjacent electrode, the material of the adjacent photoconductive layer 30 and the like, and 1.3 eV or more from the work function (Wf) of the material of the adjacent electrode. A material having a large ionization potential (Ip) and an Ea equivalent to or larger than the electron affinity (Ea) of the material of the adjacent photoconductive layer 30 is preferable. Since the material applicable as the electron-accepting organic material is described in detail in Japanese Patent Application Laid-Open No. 2009-32854, description thereof is omitted.

  In the case where the bias voltage is set so that the holes move to the bias electrode 32 and the electrons move to the charge collecting electrode 34 among the charges generated in the photoconductive layer 30, the electron blocking film and the hole blocking are set. What is necessary is just to reverse the position of a film | membrane. Moreover, it is not necessary to provide both the electron blocking film and the hole blocking film. If either one is provided, a certain degree of dark current suppressing effect can be obtained.

3 shows the structure of the switch element 24 is shown schematically.

The TFT substrate 26, corresponding to the charge collecting electrode 34, the switch element 24 for converting an electrical signal charge transferred to the charge collecting electrode 34 is formed. Forming regions of the switch element 24 has a portion overlapping with the charge collecting electrode 34 in plan view, by adopting such a configuration, the switch element 24 in each pixel portion and the sensor portion 36 And have an overlap in the thickness direction. Incidentally, the radiation detector 20 to the plane area of the (pixel portion) in order to minimize, it is desirable to form regions of switches element 24 is completely covered by the charge collecting electrode 34.

Switch element 24, the gate electrode 220, the gate insulating film 222, and an active layer (channel layer) 224 are stacked and further, forming the source electrode 226 and the drain electrode 228 on the active layer 224 with a predetermined gap Has been.

The drain electrode 228 is electrically connected to the corresponding charge collection electrode 34 through a wiring made of a conductive material formed through an insulating film 219 provided between the insulating substrate 22 and the charge collection electrode 34. Has been. Thus, it is possible to move the collected charges in the charge collecting electrode 34 to the switch element 24.

  The active layer 224 can be formed of, for example, amorphous silicon, amorphous oxide, organic semiconductor material, carbon nanotube, or the like. Note that the material forming the active layer 224 is not limited thereto.

The amorphous oxide that can form the active layer 224 is preferably an oxide containing at least one of In, Ga, and Zn (for example, In—O-based), and at least two of In, Ga, and Zn. Oxides containing one (for example, In—Zn—O, In—Ga—O, and Ga—Zn—O) are more preferable, and oxides including In, Ga, and Zn are particularly preferable. As the In—Ga—Zn—O-based amorphous oxide, an amorphous oxide whose composition in a crystalline state is represented by InGaO ₃ (ZnO) _m (m is a natural number less than 6) is preferable, and InGaZnO is particularly preferable. ₄ is more preferable. Note that the amorphous oxide that can form the active layer 224 is not limited thereto.

  Examples of the organic semiconductor material that can form the active layer 224 include, but are not limited to, phthalocyanine compounds, pentacene, vanadyl phthalocyanine, and the like. In addition, about the structure of a phthalocyanine compound, since it is demonstrated in detail in Unexamined-Japanese-Patent No. 2009-212389, description is abbreviate | omitted.

Active layer 224 of an amorphous oxide, an organic semiconductor material of the switch element 24, if those formed with carbon nanotube, does not absorb radiation such as X-rays, or since the stay extremely small amount as absorbed , it is possible to effectively suppress the generation of noise in the switch element 24.

Also, when forming the active layer 224 with the carbon nanotube, it is possible to speed up the switching speed of the switch element 24, also to form a switch element 24 low absorption degree of light in the visible light region . In the case of forming the active layer 224 by the carbon nanotubes, only the active layer 224 to the very small amount of metallic impurities is mixed, since the performance of the switch element 24 is significantly reduced, the very high purity by such as centrifugation It is necessary to separate and extract carbon nanotubes.

  Here, any of the above-described amorphous oxide, organic semiconductor material, carbon nanotube, and organic photoelectric conversion material can be formed at a low temperature. Therefore, the insulating substrate 22 is not limited to a highly heat-resistant substrate such as a semiconductor substrate, a quartz substrate, and a glass substrate, and a flexible substrate such as plastic, aramid, or bionanofiber can also be used. Specifically, flexible materials such as polyesters such as polyethylene terephthalate, polybutylene phthalate, polyethylene naphthalate, polystyrene, polycarbonate, polyethersulfone, polyarylate, polyimide, polycycloolefin, norbornene resin, poly (chlorotrifluoroethylene), etc. A conductive substrate can be used. If such a plastic flexible substrate is used, it is possible to reduce the weight, which is advantageous for carrying around, for example.

The insulating substrate 22 includes an insulating layer for ensuring insulation, a gas barrier layer for preventing permeation of moisture and oxygen, an undercoat layer for improving flatness or adhesion to electrodes, and the like. May be provided.

  Since aramid can be applied at a high temperature process of 200 ° C. or more, the transparent electrode material can be cured at a high temperature to reduce the resistance, and can also be used for automatic mounting of a driver IC including a solder reflow process. Moreover, since aramid has a thermal expansion coefficient close to that of ITO (indium tin oxide) or a glass substrate, warping after production is small and it is difficult to crack. In addition, aramid can form a substrate thinner than a glass substrate or the like. The insulating substrate 22 may be formed by laminating an ultrathin glass substrate and aramid.

  Bionanofiber is a composite of cellulose microfibril bundles (bacterial cellulose) produced by bacteria (Acetobacter Xylinum) and a transparent resin. The cellulose microfibril bundle has a width of 50 nm and a size of 1/10 of the visible light wavelength, and has high strength, high elasticity, and low thermal expansion. By impregnating and curing a transparent resin such as an acrylic resin or an epoxy resin in bacterial cellulose, a bio-nanofiber having a light transmittance of about 90% at a wavelength of 500 nm can be obtained while containing 60-70% of the fiber. Bionanofiber has a low coefficient of thermal expansion (3-7ppm) comparable to silicon crystals, and is as strong as steel (460MPa), highly elastic (30GPa), and flexible, compared to glass substrates, etc. A thin insulating substrate 22 can be formed.

In this embodiment, on the insulating substrate 22, the switch element 24, the sensor unit 36, a transparent flattening layer 38 are sequentially formed, the low light-absorbing property on the insulating substrate 22 adhesive resin The radiation detector 20 is formed by affixing the scintillator layer 28 with the adhesive layer 39 used. Hereinafter, the insulating substrate 22 formed up to the planarizing layer 38 is referred to as a TFT substrate 26.

  As shown in FIG. 2, the sensor unit 36 is two-dimensionally arranged on the TFT substrate 26, and the switch element 24 is two-dimensionally arranged on the insulating substrate 22 correspondingly.

  The TFT substrate 26 is extended in a certain direction (row direction) and a plurality of gate wirings 40 for turning on / off each switch element 24, and in a direction orthogonal to the gate wirings 40 (column direction). A plurality of data wirings 42 for reading out electric charges through the switch element 24 in the on state are provided.

  A flattening layer 38 for flattening the TFT substrate 26 is formed on the TFT substrate 26. An adhesive layer 39 for bonding the scintillator layer 28 to the TFT substrate 26 is formed between the TFT substrate 26 and the scintillator layer 28 and on the planarizing layer 38.

  The TFT substrate 26 is flat and has a quadrilateral shape having four sides on the outer edge in plan view. Specifically, it is formed in a rectangular shape.

  Here, as shown in FIG. 4, the radiation detector 20 is irradiated with radiation from the front side to which the scintillator layer 28 is bonded (also referred to as front side irradiation, back side reading method (so-called PSS (Penetration Side Sampling) method)). Alternatively, radiation may be applied from the TFT substrate 26 side (back side) (backside irradiation, surface reading method (also referred to as so-called ISS (Irradiation Side Sampling) method)), and the radiation detector 20 is irradiated with radiation from the front side. In this case, when light is emitted more strongly on the upper surface side (opposite side of the TFT substrate 26) of the scintillator layer 28 and radiation is irradiated from the back side, the radiation transmitted through the TFT substrate 26 enters the scintillator layer 28 and enters the scintillator layer 28. The TFT substrate 26 side emits light more intensely, and each photoconductive layer 30 is charged by the light generated in the scintillator layer 28. Therefore, radiation is generated. The ejector 20 can be designed with high sensitivity to radiation because radiation does not pass through the TFT substrate 26 when radiation is irradiated from the front side compared to when radiation is irradiated from the back side. Moreover, since the light emission position of the scintillator layer 28 with respect to each photoconductive layer 30 is closer when the radiation is irradiated from the back side than when the radiation is irradiated from the front side, the resolution of the radiographic image obtained by imaging is higher.

  That is, the radiation detector 20 has different characteristics of radiographic images taken when radiation is irradiated on one flat surface side and when radiation is irradiated on the other flat surface side.

  FIG. 5 shows an example of changes in the thickness and sensitivity of the scintillator layer 28 when the radiation detector 20 is irradiated with radiation on the front surface and when the radiation detector 20 is irradiated with back radiation. FIG. 6 shows changes in the thickness and MTF (Modulation Transfer Factor) of the scintillator layer 28 when the radiation detector 20 is irradiated with radiation from the front surface and when the radiation detector 20 is irradiated with radiation from the back surface. An example is shown.

  Next, the configuration of an electronic cassette incorporating such a radiation detector 20 will be described.

  An electronic cassette 10A as shown in FIGS. 7 to 9 is formed in a flat plate shape so that a radiation image can be taken by radiation applied on either one side or the other side of the radiation detector 20. Then, a configuration for reversing the whole, a configuration for enabling opening and closing of the electronic cassette 10B as shown in FIGS. 10 to 12, and a configuration for enabling reversing a part of the electronic cassette 10 as shown in FIGS. it can.

  Hereinafter, the configuration of the electronic cassettes 10A to 10C will be described.

  7 is a perspective view showing the configuration of the electronic cassette 10A, and FIG. 8 is a cross-sectional view of the electronic cassette 10A.

  The electronic cassette 10A includes a flat casing 18 made of a material that transmits the radiation X, and has a waterproof and airtight structure. The above-described radiation detector 20 is disposed inside the housing 18. The housing 18 has imaging regions 18A and 18B in which radiation is irradiated at the time of imaging in regions corresponding to the arrangement positions of the radiation detectors 20 on one surface of the flat plate and the other surface. The radiation detector 20 is built in such that the scintillator layer 28 is on the imaging region 18A side and the TFT substrate 26 is on the imaging region 18B side, and the imaging region 18A irradiates the radiation detector 20 with radiation from the front side. The imaging region for irradiation and the imaging region 18B are imaging regions for backside irradiation that irradiate the radiation detector 20 with radiation from the back side.

  In addition, a case 31 that accommodates a control unit 50 and a power supply unit 70 described later is disposed at one end inside the housing 18 at a position that does not overlap the radiation detector 20 (outside the range of the imaging regions 18A and 18B). ing. Here, since the electronic cassette 10A enables radiographic images to be captured on both sides of the imaging areas 18A and 18B, a member that affects the radiographic image such as a circuit or an element is not disposed in the imaging areas 18A and 18B. Yes.

  Further, the electronic cassette 10 </ b> A is provided with an operation panel 19 having various buttons on the side surface of the housing 18.

  FIG. 9 is a block diagram showing a main configuration of the electrical system of the electronic cassette 10A.

  In the radiation detector 20, a gate line driver 52 is disposed on one side of two adjacent sides, and a signal processing unit 54 is disposed on the other side.

  Inside the housing 18, an image memory 56, a cassette control unit 58, and a wireless communication unit 60 are provided as the control unit 50.

  Individual gate lines 40 of the radiation detector 20 are connected to a gate line driver 52, and individual data lines 42 are connected to a signal processing unit 54.

  Each switch element 24 is sequentially turned on in a row unit by a signal supplied from the gate line driver 52 via the gate wiring 40, and the charges read by the switch elements 24 that are turned on are converted into data wiring as electrical signals. 42 is transmitted and input to the signal processing unit 54. As a result, the charges are sequentially read out in units of rows, and a two-dimensional radiation image can be acquired.

  Although not shown, the signal processing unit 54 includes an amplification circuit and a sample hold circuit for amplifying an input electric signal for each individual data wiring 42, and the electric signal transmitted through the individual data wiring 42. Is amplified by the amplifier circuit and then held in the sample hold circuit. Further, a multiplexer and an A / D (analog / digital) converter are connected in order to the output side of the sample and hold circuit, and the electric signals held in the individual sample and hold circuits are sequentially (serially) input to the multiplexer. The digital image data is converted by an A / D converter.

  An image memory 56 is connected to the signal processing unit 54, and image data output from the A / D converter of the signal processing unit 54 is sequentially stored in the image memory 56. The image memory 56 has a storage capacity capable of storing a predetermined number of image data, and image data obtained by imaging is sequentially stored in the image memory 56 each time a radiographic image is captured.

  The image memory 56 is connected to the cassette control unit 58. The cassette control unit 58 is constituted by a microcomputer, and includes a CPU (central processing unit) 58A, a memory 58B including a ROM and a RAM, a nonvolatile storage unit 58C including a flash memory, and the like, and operates the entire electronic cassette 10A. Control.

  A wireless communication unit 60 is connected to the cassette control unit 58. The wireless communication unit 60 corresponds to a wireless local area network (LAN) standard represented by IEEE (Institute of Electrical and Electronics Engineers) 802.11a / b / g / n, etc. Control the transmission of various information between them. The cassette control unit 58 can wirelessly communicate with an external device that controls the entire radiographic imaging such as a console via the wireless communication unit 60, and can transmit and receive various types of information to and from the console. . The cassette control unit 58 stores various information such as imaging conditions received from the console via the wireless communication unit 60, and starts reading out charges based on the imaging conditions.

  In addition, the operation control unit 19 is connected to the cassette control unit 58, and the operation content for the operation panel 19 can be grasped.

  Further, the electronic cassette 10 is provided with a power supply unit 70, and the various circuits and elements described above (the operation panel 19, the gate line driver 52, the signal processing unit 54, the image memory 56, the wireless communication unit 60, and the cassette control). The microcomputer functioning as the unit 58 is operated by the electric power supplied from the power supply unit 70. The power supply unit 70 incorporates a battery (a rechargeable secondary battery) so as not to impair the portability of the electronic cassette 10, and supplies power from the charged battery to various circuits and elements. In FIG. 9, the power supply unit 70 and various circuits and wirings for connecting each element are omitted.

  The electronic cassette 10A is provided with an imaging area 18A for front side illumination and an imaging area 18B for back side illumination. By inverting the whole, radiographic images can be taken in the imaging area 18A or the imaging area 18B. Yes.

  The electronic cassette 10A is arranged at a distance from a radiation generator 80 for generating radiation, as shown in FIG. 8, with the imaging region used for imaging being taken up when imaging a radiographic image, and the patient is placed on the imaging region. The imaging target region B is arranged. The radiation generation apparatus 80 emits radiation having a radiation dose according to imaging conditions given in advance. The radiation X emitted from the radiation generator 80 is irradiated to the electronic cassette 10 after carrying image information by passing through the imaging target region B.

  The radiation X irradiated from the radiation generator 80 reaches the electronic cassette 10 after passing through the imaging target region B. As a result, charges corresponding to the dose of the irradiated radiation X are collected and accumulated in each charge collecting electrode 34 of the radiation detector 20 incorporated in the electronic cassette 10.

  The cassette control unit 58 controls the gate line driver 52 after the irradiation of the radiation X, and outputs an ON signal to each gate wiring 40 sequentially from the gate line driver 52 line by line, and connects each gate wiring 40 to each gate wiring 40. The switch elements 24 are turned on in order line by line. As a result, the charges accumulated in each charge collecting electrode 34 in order line by line flow out to each data wiring 42 as an electrical signal. The electric signal flowing out to each data wiring 42 is input to the signal processing unit 54, converted into digital image information, and stored in the image memory 56.

  The cassette control unit 58 transmits the image information stored in the image memory 56 to the console after the photographing is completed. In addition, although the case where a still image is imaged has been described, moving image shooting may be performed by continuously performing image capturing.

  As described above, the electronic cassette 10A according to the present embodiment can easily capture radiographic images having different characteristics by inverting the whole and performing imaging in the imaging region 18A or the imaging region 18B.

  Next, the configuration of the electronic cassette 10B will be described.

  10 and 11 are perspective views showing the configuration of the electronic cassette 10B according to the embodiment, and FIG. 12 is a cross-sectional view showing the schematic configuration of the electronic cassette 10B. Note that portions corresponding to those of the electronic cassette 10A (see FIGS. 7 to 9) are denoted by the same reference numerals, and description of portions having the same functions is omitted.

  The electronic cassette 10B includes a radiation detector 20, a gate line driver 52, and a signal processing unit 54, and includes a flat imaging unit 12 that captures a radiographic image of the irradiated radiation, and a control unit 50 and a power supply unit 70. The control unit 14 is connected by a hinge 16 so that it can be opened and closed.

  The photographing unit 12 and the control unit 14 are rotated with the hinge 16 at the center of rotation while the other is in the unfolded state (FIG. 11) in which the photographing unit 12 and the control unit 14 are aligned, and the photographing unit. 12 and the control unit 14 can be opened and closed in the storage state (FIG. 10) folded and overlapped.

  The electronic cassette 10 </ b> B is provided with an operation panel 19 on the upper surface of the control unit 14.

  As shown in FIG. 12, the imaging unit 12 has a built-in radiation detector 20 so that the scintillator layer 28 is on the control unit 14 side and the TFT substrate 26 is on the outside (opposite side of the control unit 14 side). In addition, the outer surface in the storage state is an imaging region 18B (FIG. 10) for irradiating the radiation detector 20 from the back side, and the surface facing the control unit 14 is the radiation detector 20. The imaging region 18A (FIG. 11) for surface irradiation that irradiates radiation from the front side.

  The radiation detector 20, the control unit 50, and the power supply unit 70 are connected by a connection wiring 44 provided in the hinge 16.

  As described above, the electronic cassette 10B can capture a radiographic image in the imaging region 18B for backside illumination in the housed state, and can capture a radiographic image in the imaging region 18A for surface illumination in the unfolded state. The radiographic images having different characteristics can be easily captured by opening and closing and performing imaging in the imaging region 18A or the imaging region 18B.

  Next, the configuration of the electronic cassette 10C will be described.

  13 and 14 are perspective views showing the configuration of the electronic cassette 10C according to the embodiment, and FIG. 15 is a cross-sectional view showing the schematic configuration of the electronic cassette 10C. The parts corresponding to those of the electronic cassette 10A (see FIGS. 7 to 9) and the electronic cassette 10B (see FIGS. 10 to 12) are denoted by the same reference numerals, and the parts having the same functions are described. Omitted.

  The electronic cassette 10C includes a radiation detector 20, a gate line driver 52, and a signal processing unit 54, and includes a flat imaging unit 12 that captures a radiographic image of the irradiated radiation, and a control unit 50 and a power supply unit 70. The control unit 14 is connected to a rotary shaft 17 so as to be rotatable. The radiation detector 20, the control unit 50, and the power supply unit 70 are connected by a connection wiring 44 provided on the rotating shaft 17.

  The imaging unit 12 is provided with imaging regions 18A and 18B on one surface and the other surface of the flat plate corresponding to the position where the radiation detector 20 is disposed.

  The electronic cassette 10 </ b> C is provided with an operation panel 19 on the upper surface of the control unit 14.

  The radiation detector 20 is built in such that the scintillator layer 28 is on the imaging region 18A side and the TFT substrate 26 is on the imaging region 18B, and the imaging region 18A irradiates the radiation detector 20 with radiation from the front side. The imaging region for imaging, the imaging region 18B, is an imaging region for backside irradiation that irradiates the radiation detector 20 with radiation from the back side.

  The radiation detector 20, the control unit 50, and the power supply unit 70 are connected by a connection wiring 44 provided in the rotary shaft 17.

  The imaging unit 12 and the control unit 14 are rotated with respect to the other so that the imaging area 18A and the operation panel 19 are aligned (FIG. 13), and the imaging area 18B and the operation panel 19 are aligned. (FIG. 14).

  As described above, the electronic cassette 10B can capture a radiographic image in the imaging region 18A for surface irradiation in a state where the imaging region 18A and the operation panel 19 are aligned (FIG. 13). 19 (FIG. 14), the radiographic image can be captured in the imaging region 18B for backside illumination, and by rotating and imaging in the imaging region 18A or the imaging region 18B, characteristics of Different radiographic images can be taken easily.

[Second Embodiment]
Next, a second embodiment will be described.

  FIG. 16 is a cross-sectional view schematically showing the configuration of the radiation detector 20 according to the second exemplary embodiment. In addition, the same code | symbol is attached | subjected about the part corresponding to the radiation detector 20 (refer FIGS. 1-4) of 1st Embodiment, and description is abbreviate | omitted about the part which has the same function.

  In the radiation detector 20 according to the present embodiment, two scintillator layers 28 (28A, 28B) are formed on both surfaces of the TFT substrate 26.

  Since the two scintillator layers 28 are formed on both surfaces of the TFT substrate 26, the radiation detector 20 of the present embodiment performs surface irradiation regardless of whether the radiation detector 20 is irradiated with radiation from either the front or the back.

  Here, the specific light emission of the scintillator layer 28 varies depending on the thickness as shown in FIGS.

  The thicker the scintillator layer 28, the more light is emitted and the higher the sensitivity, but the image quality is degraded by light scattering or the like.

  Therefore, by setting the thickness of the scintillator layers 28A and 28B to be the scintillator layer 28B> the scintillator layer 28A, the scintillator layer 28A side can be focused on image quality, and the scintillator layer 28B side can be focused on sensitivity. If the scintillator layer 28 is less than 50 μm, a sufficient output for X-rays cannot be obtained. In the case of surface irradiation, if it exceeds 300 μm, the reflected light will be scattered and absorbed in the scintillator, and the amount of light that appears on the surface Tends to be insufficient. When used for surface irradiation, the scintillator layer 28 preferably has a thickness in the range of 50 to 300 μm, and more preferably in the range of 100 to 250 μm.

  The scintillator layer 28 is filled in the scintillator layer 28, and the larger the particle size of the particles that emit light when irradiated with radiation, the greater the amount of light emission and the higher the sensitivity. Since the particles that are present affect adjacent pixels, the image quality is degraded.

  Therefore, by setting the particle size of the scintillator layers 28A and 28B to scintillator layer 28B> scintillator layer 28A, the scintillator layer 28A side can be focused on image quality, and the scintillator layer 28B side can be focused on sensitivity.

Further, the scintillator layer 28 can have a multilayer structure of small particles and large particles. For example, as shown in FIG. 17, although a small blur of the image towards the scintillator layer 28 irradiated side and the region 25A of the small particles a TFT substrate 26 side and a region 25B of the large particles, originating radially small particles It is difficult for the oblique component of the light to reach the TFT substrate 26, and the sensitivity is lowered. In addition, the sensitivity is increased by changing the ratio of the region 25A and the region 25B to increase the large particle layer relative to the small particle layer, but the image quality deteriorates because light scattering affects the adjacent pixels. To do.

  Therefore, by changing the layered structure of the particles of the scintillator layers 28A and 28B, the scintillator layer 28A side can be focused on image quality, and the scintillator layer 28B side can be focused on sensitivity.

  Further, the scintillator layer 28 has higher sensitivity as the filling rate is higher, but light scattering increases and image quality is degraded. Here, the filling rate is a value obtained by dividing the total volume of particles of the scintillator layer 28 / the volume of the scintillator layer 28 × 100. In addition, since the scintillator layer 28 is difficult to manufacture when handling powder and the filling rate exceeds 80%, the filling rate is preferably 50 to 80% by volume.

  Therefore, by setting the particle filling rate of the scintillator layers 28A and 28B to scintillator layer 28B> scintillator layer 28A, the scintillator layer 28A side can be focused on image quality, and the scintillator layer 28B side can be focused on sensitivity.

  The scintillator layer 28 also has a specific emission change depending on the amount of activator doped, and the amount of emitted light tends to increase as the amount of activator doped increases, but the amount of light scattering increases and image quality decreases. .

  Therefore, by setting the scintillator layers 28A and 28B to have an activator doping amount of scintillator layer 28B> scintillator layer 28A, the scintillator layer 28A side can be focused on image quality, and the scintillator layer 28B side can be focused on sensitivity.

  Further, the scintillator layer 28 has different emission specifications for radiation by changing the material used.

  For example, when the scintillator layer 28A is formed of GOS and the scintillator layer 28B is formed of CsI: Tl, the scintillator layer 28A is focused on sensitivity, and the scintillator layer 28B is focused on image quality.

  In addition, the scintillator layer 28 has a flat or columnar layer structure, so that the emission specification for radiation is different.

  For example, when the scintillator layer 28A has a flat layer structure and the scintillator layer 28B has a columnar separation layer structure, the scintillator layer 28A is focused on sensitivity, and the scintillator layer 28B is focused on image quality.

In addition, as shown in FIG. 18, by forming a reflective layer 29 that transmits X-rays and reflects visible light on the surface of the scintillator layer 28 opposite to the TFT substrate 26, the generated light is more efficiently generated. Since it can be led to the TFT substrate 26, the sensitivity is improved. The reflective layer may be provided by any of sputtering, vapor deposition, and coating methods. The reflective layer 29 is preferably a material that is highly reflective in the emission wavelength region of the scintillator layer 28 to be used, such as Au, Ag, Cu, Al, Ni, Ti. For example, the scintillator layer 28 GOS: For Tb, wavelength Ag having high reflectance at 400 to 600 nm, Al, Cu, etc. well, the thickness is not obtained reflectivity is less than 0.01 [mu] m, a 3.mu. m because not obtained on improvement of the reflectance exceeds, 0.01 to 3 [mu] m is preferred.

  Here, the scintillator layer 28 is formed by combining particle diameter, particle multilayer structure, particle filling rate, activator dope amount, material, layer structure change, and formation of the reflective layer 29. Needless to say, the characteristics can be different.

  In the present embodiment, the thickness of the scintillator layers 28A and 28B, the particle diameter, the particle multilayer structure, the particle filling rate, the activator dope amount, the material and the layer structure are changed, or the reflective layer 29 is formed. Thus, the characteristics of the radiographic image to be taken are different depending on whether the radiation is applied to one flat surface of the radiation detector 20 or the other surface of the flat plate. Therefore, by incorporating the electronic cassettes 10A to 10C in the above-described manner, radiographic images having different characteristics can be easily taken.

[Third Embodiment]
Next, a third embodiment will be described.

  FIG. 19 is a cross-sectional view schematically showing the configuration of the radiation detector 20 according to the third exemplary embodiment. In addition, the same code | symbol is attached | subjected about the part corresponding to the radiation detector 20 (refer FIGS. 1-4) of 1st Embodiment, and description is abbreviate | omitted about the part which has the same function.

  As shown in FIG. 19, the radiation detector 20 is provided with TFT substrates 26 (26 </ b> A, 26 </ b> B) on both surfaces of one scintillator layer 28.

  As described above, since the TFT substrates 26A and 26B are provided on both surfaces of the scintillator layer 28, the radiation detector 20 according to the present embodiment performs back-surface irradiation regardless of whether the radiation is irradiated from the front or the back.

  In the present embodiment, for example, the material of the photoconductive layer 30 of the TFT substrates 26A and 26B is changed, or a filter is formed between the TFT substrate 26A and the scintillator layer 28, or between the TFT substrate 26B and the scintillator layer 28. Alternatively, the light receiving area of the photoconductive layer 30 functioning as a photodiode is changed between the TFT substrate 26A and the TFT substrate 26B so that the light receiving area is wider than the side where importance is placed on the image quality. By changing the pixel pitch with the substrate 26B so that the pixel pitch is narrower than the sensitivity-oriented side, or by changing the signal readout characteristics of the TFT substrates 26A and 26B, the light of the TFT substrates 26A and 26B is changed. The light-receiving characteristics for are changed.

  By changing the light receiving characteristics of the TFT substrates 26A and 26B with respect to the light, when radiation is applied to one flat surface of the radiation detector 20 and when the other light is irradiated to the other surface of the flat plate Therefore, it is possible to easily capture radiographic images having different characteristics by incorporating them in the above-described electronic cassettes 10A to 10C.

  FIG. 20 is a block diagram showing a main configuration of the electric system when the radiation detector 20 according to the present embodiment is built in the electronic cassette 10A.

  The radiation detector 20 is incorporated so that the TFT substrate 26A is on the imaging region 18A side and the TFT substrate 26B is on the imaging region 18B side.

  The electronic cassette 10A may be provided with a gate line driver 52 and a signal processing unit 54 corresponding to the TFT substrates 26A and 26B. FIG. 20 shows a configuration in which gate line drivers 52A and 52B and signal processing units 54A and 54B are provided corresponding to the TFT substrates 26A and 26B in the electronic cassette 10A.

  The cassette control unit 58 controls the operation of the gate line drivers 52A and 52B, and captures radiographing surface information indicating which one of the imaging area 18A and the imaging area 18B performs imaging from the console during imaging. Receive via. Then, the cassette control unit 58 reads the image by controlling the gate line driver 52 corresponding to the imaging region specified by the imaging surface information after the irradiation of the radiation X is completed.

  Thereby, radiographic images can be captured in the imaging region 18A and the imaging region 18B.

[Fourth Embodiment]
Next, a fourth embodiment will be described.

  FIG. 21 is a cross-sectional view schematically showing the configuration of the radiation detector 20 according to the fourth exemplary embodiment. In addition, the same code | symbol is attached | subjected about the part corresponding to the radiation detector 20 (refer FIGS. 1-4) of 1st Embodiment, and description is abbreviate | omitted about the part which has the same function.

As shown in FIG. 2 1, the radiation detector 20 includes two TFT substrate 26 (26A, 26B) and two of the scintillator layer 28 (28A, 28B) and, a radiation shielding plate 27 for shielding radiation .

In the radiation detector 20 according to the present embodiment, the scintillator layer 28A and the TFT substrate 26A are sequentially provided on one surface of the radiation shielding plate 27, and the scintillator layer 28B and the TFT substrate 26B are sequentially disposed on the other surface of the radiation shielding plate 27. Is provided.

  In this way, by providing the scintillator layer 28A and the TFT substrate 26A in this order on one surface of the radiation shielding plate 27, the scintillator layer 28A and the TFT substrate 26A are irradiated with radiation from the one surface side, so that the radiation is irradiated. By providing the scintillator layer 28B and the TFT substrate 26B in this order on the other surface of the shielding plate 27, the scintillator layer 28B and the TFT substrate 26B are irradiated with radiation from the other surface side. Further, since the radiation detector 20 is provided with the radiation shielding plate 27, the radiation irradiated from one surface side does not transmit to the other surface side, and the radiation irradiated from the other surface side is one surface. It does not penetrate to the side.

  In the present embodiment, the scintillator layers 28A and 28B are changed in thickness, particle size, particle multilayer structure, filling rate, activator dope amount, material, layer structure, reflective layer 29, TFT substrate, etc. The material of the photoconductive layer 30 of 26A and 26B is changed, or a filter is formed between the TFT substrate 26A and the scintillator layer 28, between the TFT substrate 26B and the scintillator layer 28, or between the TFT substrate 26A and the TFT substrate 26B. The light receiving area of the photoconductive layer 30 functioning as a photodiode is changed so that the light receiving area is wider than the side where importance is placed on the image quality, or the pixel pitch is changed between the TFT substrate 26A and the TFT substrate 26B. Radiation was applied to one flat surface of the radiation detector 20 by making the pitch narrower than the image quality-oriented side. Since the characteristics of the radiographic image to be taken can be made different depending on whether the other surface side of the flat plate is irradiated with radiation, radiation having different characteristics can be obtained by incorporating it in the above-described electronic cassettes 10A to 10C. You can easily take images.

  When the radiation detector 20 according to the present embodiment is built in the above-described electronic cassettes 10A to 10C, since the radiation detector 20 includes two TFT substrates 26A and 26B, the electronic cassettes 10A to 10C are the third ones. Similarly to the embodiment, the gate line drivers 52A and 52B and the signal processing units 54A and 54B may be provided corresponding to the TFT substrates 26A and 26B.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various modifications or improvements can be added to the above-described embodiment without departing from the gist of the invention, and embodiments to which such modifications or improvements are added are also included in the technical scope of the present invention.

  The above embodiments do not limit the invention according to the claims (claims), and all the combinations of features described in the embodiments are essential for the solution means of the invention. Is not limited. The embodiments described above include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. Even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, as long as an effect is obtained, a configuration from which these some constituent requirements are deleted can be extracted as an invention.

  In each of the above embodiments, the case where the gate line driver 52 and the signal processing unit 54 of the electronic cassettes 10B and 10C are provided in the photographing unit 12 has been described, but the present invention is not limited to this. For example, the gate line driver 52 and the signal processing unit 54 may be configured by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) and disposed in the hinge 16 or the rotary shaft 17. Thereby, the cooling effect of the integrated circuit can be enhanced.

  In each of the above embodiments, the present invention is applied to the radiation detector 20 of the indirect conversion system in which radiation is once converted into light by the scintillator layer 28, and the converted light is converted into charges by the photoconductive layer 30 and stored. However, the present invention is not limited to this, for example, a sensor that uses amorphous selenium or the like directly on one surface side of the radiation detector 20 of the fourth embodiment. Alternatively, a direct conversion method may be used in which the charge is converted and stored in the unit.

  As shown in FIG. 22, in the direct conversion type radiation detector, as an example of a radiation conversion layer for converting incident radiation, a photoconductive layer 48 for converting incident radiation into electric charges is formed on the TFT substrate 26. Is formed.

As the photoconductive layer 48, amorphous Se, Bi ₁₂ MO ₂₀ (M: Ti, Si, Ge), Bi ₄ M ₃ O ₁₂ (M: Ti, Si, Ge), Bi ₂ O ₃ , BiMO ₄ (M: Nb, Ta, V), Bi ₂ WO ₆ , Bi ₂₄ B ₂ O ₃₉ , ZnO, ZnS, ZnSe, ZnTe, MNbO ₃ (M: Li, Na, K), PbO, HgI ₂ , PbI ₂ , CdS, CdSe , CdTe, BiI ₃ , GaAs, etc. are used as a main component, but they have high dark resistance, good photoconductivity against X-ray irradiation, and low temperature by vacuum deposition. An amorphous material capable of forming a large area is preferred.

  On the photoconductive layer 48, a bias electrode 49 that is formed on the surface side of the photoconductive layer 48 and applies a bias voltage to the photoconductive layer 48 is formed.

  In the direct conversion type radiation detection apparatus, as in the indirect conversion type radiation detection apparatus, a charge collection electrode 34 that collects the charges generated in the photoconductive layer 48 is formed on the TFT substrate 26.

  Further, the TFT substrate 26 in the direct conversion type radiation detection apparatus includes a charge storage capacitor 35 for storing the charges collected by the charge collection electrodes 34. The charge accumulated in each charge storage capacitor 35 is read out by the switch element 24.

  In the fourth embodiment, the case where both the one surface and the other surface of the radiation detector 20 are configured to be back-illuminated has been described. However, the present invention is not limited to this. One or both of one surface and the other surface may be configured as surface irradiation.

In each embodiment, the case of taking a still image has been described. However, the present invention is not limited to this, and moving image shooting may be performed. Because movie shooting repeated continuously shooting, the calorific value is large. Thus, for example, as in the electronic cassette 10B, if the openable structure of the imaging unit 12 and the control unit 14, to allow the still image shooting in the accommodated state, cooling to allow moving image shooting in the deployed state From the point of view, it is preferable.

  By the way, as shown in FIG. 23, the sensitivity of CsI decreases as the cumulative exposure dose increases, and the sensitivity decreases when the CsI is maintained in a state where no radiation is irradiated.

  Therefore, for example, as shown in FIGS. 16 and 21, the scintillator layers 28A and 28B of the radiation detector 20 having the two scintillator layers 28 (28A and 28B) are formed of CsI (for example, CsI: Tl columnar crystals). To do. Then, the radiation detector 20 is built in the electronic cassettes 10A to 10C so that radiographic images can be captured on one surface and the other surface (imaging regions 18A and 18B). In this case, in the electronic cassettes 10A to 10C, the doses of radiation irradiated on one surface and the other surface are detected, respectively, and the cumulative exposure doses on the one surface and the other surface are stored, respectively. When the estimated sensitivity of the scintillator layer 28 is lower than a predetermined allowable sensitivity that affects the image quality of the radiographic image to be captured, photographing on the surface where the sensitivity of the scintillator layer 28 is lower than the allowable sensitivity is prohibited. It is also possible to encourage shooting on the opposite side. In particular, since the radiation detector 20 shown in FIG. 21 is shielded from radiation by the radiation shielding plate 27, the scintillator layer 28 on the surface that has exceeded the allowable value can be rested without being irradiated with radiation. Detection of the dose of irradiated radiation may be performed by providing a sensor capable of detecting radiation inside the electronic cassettes 10A to 10C, or from the pixel value of each pixel of the captured radiation image. (For example, the cumulative value of the pixel values of all the pixels is regarded as the dose of the irradiated radiation). The prohibition of shooting when the sensitivity of the scintillator layer 28 is less than the allowable sensitivity may be notified to the photographer via an external device such as a console, and a display unit or the like is provided on the operation panel 19. The display may be performed.

  Also, CsI recovers quickly from the reduced sensitivity when stored in a high temperature environment. Moreover, CsI can suppress the fall of a sensitivity, the one where use environment temperature is high. Therefore, for example, as shown in FIGS. 16 and 21, one scintillator layer 28A of the radiation detector 20 having two scintillator layers 28 (28A, 28B) is formed of CsI (for example, CsI: Tl columnar crystal). Then, the other scintillator layer 28B is formed by GOS. The radiation detector 20 is built in an openable / closable electronic cassette 10B so that a radiation image can be captured on one surface and the other surface (imaging regions 18A and 18B). In this case, as shown in FIGS. 24A and 24B, in the radiation detector 20, in the housed state, the scintillator layer 28B is on the control unit 14 side, and the scintillator layer 28A is on the outside (opposite side of the control unit 14 side). As described above, it is preferably built in the photographing unit 12. In the electronic cassette 10B, heat from the control unit 14 is easily transmitted to the photographing unit 12 in the housed state (FIG. 24A). For this reason, by disposing the scintillator layer 28A on the photographing region 18B side and using the scintillator layer 28A for photographing in the housed state, a decrease in sensitivity of the scintillator layer 28A is suppressed. On the other hand, the sensitivity of GOS hardly changes due to temperature change. For this reason, by arranging the scintillator layer 28B on the photographing region 18A side and using the scintillator layer 28B for photographing in the unfolded state (FIG. 24B), the image quality hardly changes due to the change in sensitivity due to the temperature change.

  In addition, when the scintillator layer 28 is formed of CsI, a change in the sensitivity of the scintillator layer 28 is estimated from the accumulated exposure amount, and when the sensitivity of the scintillator layer 28 becomes lower than the allowable sensitivity, the temperature of the scintillator layer 28 is maintained high. The reduced sensitivity may be recovered quickly.

  FIG. 25 shows an example of a sensitivity change of the scintillator layer 28A formed of CsI in the electronic cassette 10 having the configuration shown in FIGS. 24 (A) and 24 (B), for example.

  In the electronic cassette 10, the sensitivity of the scintillator layer 28A is reduced by performing imaging in the imaging region 18B on the first and second imaging days, and the scintillator layer is maintained in a state where no radiation is irradiated at night. The sensitivity of 28A is restored. In addition, the electronic cassette 10 is subjected to fluoroscopic imaging (moving image imaging) in which radiographic images are continuously captured in the imaging region 18B on the third day of imaging, and when the sensitivity of the scintillator layer 28A falls below the allowable sensitivity, Shooting in the shooting area 18B is prohibited, and shooting in the shooting area 18A or shooting with another electronic cassette 10 is encouraged.

  The change in sensitivity of the scintillator layer 28A on each shooting date is, for example, when calibration is performed to calibrate the apparatus state by first irradiating the electronic cassette 10 with a predetermined amount of radiation on each shooting date. FIG. 23 shows the sensitivity of the scintillator layer 28A detected at the time of calibration by detecting the sensitivity of the scintillator layer 28A during the calibration of the day, obtaining the cumulative exposure dose irradiated during each photographing day. As shown, the sensitivity of the scintillator layer 28A may be estimated as the sensitivity decreases as the cumulative exposure increases. Further, the sensitivity of the scintillator layer 28A may be estimated from the irradiation time when radiation is irradiated in imaging, the accumulated exposure dose, and the period maintained without irradiation.

  In addition, when the sensitivity of the scintillator layer 28A becomes less than the allowable sensitivity, the electronic cassette 10 generates heat at the control unit 14 at night, for example, and warms the photographing unit 12 by the heat of the control unit 14, and the temperature of the scintillator layer 28A. The sensitivity of the scintillator layer 28A, which has been lowered, is recovered quickly by maintaining a high value. In the case where the electronic cassette 10 is stored and stored in a storage device such as a cradle, the storage device may warm the electronic cassette 10 at night to keep the temperature of the scintillator layer 28A high.

  In addition, the configurations of the electronic cassette 10 and the radiation detector 20 described in the above embodiment are merely examples, and it is needless to say that the configurations can be appropriately changed without departing from the gist of the present invention.

10A, 10B, 10C Electronic cassette 12 Imaging unit 14 Control unit 16 Hinge (connection member)
17 Rotating shaft (connecting member)
20 Radiation detector 26, 26A, 26B TFT substrate (substrate)
27 Radiation shielding plate (shielding plate)
28, 28A, 28B Scintillator layer (light emitting layer)
29 reflective layer 30 photoconductive layer

Claims (11)

In addition to being formed in a flat plate shape, the characteristics of the radiographic image taken are different when radiation is applied to one side of the flat plate and when radiation is applied to the other surface of the flat plate. A light-emitting layer that generates light when irradiated with radiation, and a substrate on which a switch element for reading out the charge is formed while charge is accumulated by receiving light generated in the light-emitting layer. A portable radiation imaging apparatus that includes a radiation detector configured as described above and that can capture a radiation image of the irradiated radiation on both the one surface side and the other surface side. Said radiation detector, wherein one of the light-emitting layer and the substrate is two provided, the light-emitting layer and the substrate and is portable radiographic imaging device according to claim 1, wherein the alternately stacked. The radiation detector is provided with two light emitting layers and two substrates , respectively, and is provided with a shielding plate for shielding radiation, and the light emitting layer is disposed on the one surface side and the other surface side of the shielding plate. portable radiographic imaging device according to claim 1, wherein the substrate is formed by laminating. Said radiation detector, said light emitting layer has two provided Rutotomoni, the two light-emitting layer having a thickness is filled in the light-emitting layer, the particle size of the particles radiation emits light by being irradiated layer of the particles At least one change in the structure, the filling rate of the particles, the doping amount of the activator, the material of the light emitting layer, and the layer structure of the light emitting layer, and the light on the surface of the light emitting layer not facing the substrate portable radiographic imaging device according to claim 2 or claim 3, wherein any one has been made of the formation of the reflective layer for reflecting. It said radiation detector, wherein the substrate is two provided Rutotomoni, portable radiographic imaging device of the two according to claim 2 or claim 3, wherein changing the read characteristics of the substrate of the signal is performed. Wherein the radiation detector is one of the one surface side and the other surface is a direct conversion method that converts a charge radiation in the semiconductor layer, converts the charge after the other is obtained by converting the radiation into light indirect conversion with claims 1 portable radiographic imaging device according. The EML phosphor portable radiographic imaging device according to any one of claims 1 to 6, which is configured to include columnar crystals of the material that emits light when radiation is irradiated. The portable radiographic apparatus according to claim 7 , wherein the phosphor material is CsI. Wherein the radiation detector is one of the one surface side and the other surface side is a characteristic of the image-quality priority, any one of claims 1 to 8 in which the other is a characteristic of sensitivity oriented The portable radiation imaging apparatus described. Is formed in a flat plate shape, the radiation detector is incorporated, the imaging unit can image a radiation image by radiation is also irradiated the flat-plate-like one side, in any of the other side,
A control unit having a built-in control unit for controlling the imaging operation of the radiation detector;
A connecting member that is openably and closably connected to an unfolded state in which the photographing unit and the control unit are aligned, and a storage state in which the photographing unit and the control unit are overlapped and folded;
A portable radiation imaging apparatus according to any one of claims 1 to 9 , further comprising: Is formed in a flat plate shape, the radiation detector is incorporated, the imaging unit can image a radiation image by radiation is also irradiated the flat-plate-like one side, in any of the other side,
A control unit having a built-in control unit for controlling the imaging operation of the radiation detector;
A connecting member that reversibly connects one surface of the photographing unit to the control unit, and the other surface;
A portable radiation imaging apparatus according to any one of claims 1 to 9 , further comprising:

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