JP2016029396A - Radiographic imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiographic imaging apparatus capable of photographing a radiation image with high sharpness while suppressing deterioration of sensitivity.SOLUTION: In a radiographic imaging apparatus, a radiation detector 20, which has a scintillator 8 for generating light by irradiation of radiation, and a TFT substrate 30 having a plurality of sensor portions 13 including organic photoelectric conversion material for generating an electric charge by receiving the light sequentially stacked thereon, is arranged so that radiation having passed through a subject B is incident from the TFT substrate 30 side.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a radiation imaging apparatus.

  2. Description of the Related Art In recent years, radiation detectors such as FPD (Flat Panel Detector) capable of directly converting radiation such as X-rays into digital data by arranging a radiation sensitive layer on a TFT (Thin Film Transistor) active matrix substrate have been put into practical use. The radiography apparatus using this radiation detector can see images immediately, compared with conventional radiography apparatuses using X-ray film or imaging plate, and radiographic imaging (moving image) (Photographing) can also be performed.

Various types of radiation detectors of this type have been proposed. For example, radiation is once converted into light by a scintillator such as CsI: Tl, GOS (Gd ₂ O ₂ S: Tb), and converted light. There is an indirect conversion method in which a sensor unit such as a photodiode converts it into electric charge and stores it. In the radiation imaging apparatus, the electric charge accumulated in the radiation detector is read as an electric signal, and the read electric signal is amplified by an amplifier and then converted into digital data by an A / D (analog / digital) converter.

  As a technique related to this type of radiation detector, Patent Document 1 discloses that a radiation detector is disposed so that radiation transmitted through a subject is incident from the scintillator side, and a part of the scintillator on the radiation irradiation side passes through the radiation. Disclosed is a technology for determining the degree of deterioration of a radiation detector by covering with a mask member made of a non-material and comparing the dark current output from the photodiodes in the region covered with the mask member and the region not covered with the mask member. Has been.

  Patent Document 2 describes a radiation detector in which a sensor portion is formed of an organic photoelectric conversion material.

JP 2002-168806 A JP 2009-32854 A

  By the way, the radiation detector may be irradiated with radiation (front surface irradiation) from the front side where the scintillator is provided, or may be irradiated with radiation (back surface irradiation) from the substrate side (back side).

  When the backside illumination is applied, the scintillator emits light near the substrate, so that a sharp image can be obtained. However, when the radiation passes through the substrate, the radiation is absorbed in the substrate and the sensitivity is high. Decreases.

  On the other hand, when the radiation detector is irradiated on the surface, there is no absorption of radiation at the substrate, so the sensitivity does not decrease. However, as the scintillator becomes thicker, the light emitted from the scintillator moves away from the substrate, so that the resulting image is sharp. The degree becomes lower.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radiation imaging apparatus that can capture a radiation image with high sharpness while suppressing a decrease in sensitivity.

  In order to achieve the above object, the radiation imaging apparatus according to claim 1 includes: a light emitting layer that generates light when irradiated with radiation; and an organic photoelectric conversion material that generates charge when receiving light. A substrate including a plurality of sensor units each including a plurality of sensor units is sequentially stacked, and a radiation detector is disposed so that radiation transmitted through the subject is incident from the substrate side.

  According to the present invention, the radiation detector includes a plurality of sensor units each including a light emitting layer that generates light when irradiated with radiation and an organic photoelectric conversion material that generates charge when receiving light. The provided substrates are sequentially stacked.

  The radiation detector is arranged so that the radiation transmitted through the subject enters from the substrate side.

  Thus, according to the first aspect of the present invention, the radiation transmitted through the subject is incident from the substrate side of the radiation imaging apparatus, passes through the substrate, reaches the light emitting layer, and causes the light emitting layer to emit light. Since the provided sensor portion receives light emitted from the light emitting layer and light emission from the light emitting layer occurs near the substrate, an image with high sharpness can be obtained. Moreover, according to this invention, since the sensor part is comprised including the organic photoelectric conversion material, and a radiation is hardly absorbed in a sensor part, the fall of a sensitivity can be suppressed.

  In the present invention, as in the invention described in claim 2, it is preferable that the substrate is composed of any one of plastic resin, aramid, bionanofiber, and a flexible glass substrate.

  Further, according to the present invention, as in the third aspect of the present invention, the substrate is configured to include an amorphous oxide in the active layer corresponding to the sensor unit, and the charge generated in each sensor unit is read out. A thin film transistor may be formed.

  Further, in the present invention, as in the invention described in claim 4, the substrate may be attached to an imaging region irradiated with radiation transmitted through a subject in the housing.

  Further, in the present invention, as in the invention described in claim 5, it is preferable that the light emitting layer includes a columnar crystal of CsI and the organic photoelectric conversion material is quinacridone.

  Further, according to the present invention, as in the sixth aspect of the present invention, the radiation detector is disposed so as to overlap a detection region provided with the plurality of sensor units, and has at least a facing surface facing the detection region. A bag body having optical transparency, a tank in which a liquid scintillator that emits light when irradiated with radiation is stored, an injection of the liquid scintillator stored in the tank into the bag body, and an injection into the bag body And an actuator for taking out the liquid scintillator.

  Moreover, this invention may arrange | position so that the two said radiation detectors from which the light emission characteristic with respect to the radiation of the said light emitting layer differs as the invention of Claim 7 may overlap.

  In the invention according to claim 7, as in the invention according to claim 8, the light emitting layers of the two radiation detectors are filled with the thickness of each light emitting layer and each light emitting layer and irradiated with radiation. The particle size of the particles that emit light, the multilayer structure of the particles, the filling rate of the particles, the doping amount of the activator, the material of each light emitting layer, and the change in the layer structure of each light emitting layer, and each light emission Any of the formation of the reflective layer that reflects the light on the surface of the layer that is not opposed to the substrate may be performed.

  Further, in the invention described in claim 1 or 2, as in the invention described in claim 9, the substrate further includes a thin film transistor for reading out the electric charge generated in the sensor unit, and the sensor The section is configured using a wide gap semiconductor substrate, and the radiation detector is stacked in the order of the light emitting layer, the sensor section, and the thin film transistor, and is arranged so that the radiation is irradiated from the thin film transistor side. It may be.

  The radiation imaging apparatus of the present invention has an excellent effect that radiographic images with high sharpness can be captured while suppressing a decrease in sensitivity.

It is a cross-sectional schematic diagram which shows schematic structure of the 3 pixel part of the radiation detector which concerns on embodiment. It is sectional drawing which showed roughly the structure of the signal output part of 1 pixel part of the radiation detector which concerns on embodiment. It is a top view which shows the structure of the radiation detector which concerns on embodiment. It is a perspective view which shows the structure of the electronic cassette concerning 1st Embodiment. It is sectional drawing which shows the structure of the electronic cassette concerning 1st Embodiment. It is a block diagram which shows the principal part structure of the electric system of the electronic cassette concerning 1st Embodiment. It is sectional drawing for demonstrating the irradiation of the surface of the radiation X to a radiation detector, and back irradiation. It is sectional drawing which shows the structure of the imaging | photography part which concerns on 2nd Embodiment. It is a schematic diagram which shows the multilayer structure of the small particle and large particle of a scintillator. 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. It is a perspective view which shows the structure of the electronic cassette concerning 2nd Embodiment. It is sectional drawing which shows the structure of the electronic cassette concerning 2nd Embodiment. It is a block diagram which shows the principal part structure of the electric system of the electronic cassette concerning 2nd Embodiment. It is sectional drawing which shows the structure of the radiation detector which concerns on another form. It is the side view which showed schematic structure of the radiography apparatus which concerns on another form. It is a perspective view which shows the structure of the electronic cassette which concerns on another form. It is sectional drawing which shows the structure of the imaging | photography part which concerns on another form. It is sectional drawing which shows the structure of the imaging | photography part which concerns on another form. It is sectional drawing which shows the structure of the imaging | photography part which concerns on another form. It is sectional drawing which shows the structure of the imaging | photography part which concerns on another form. It is a perspective view which shows the structure of the electronic cassette which can be opened and closed which concerns on another form. It is a perspective view which shows the structure of the electronic cassette which can be opened and closed which concerns on another form. It is sectional drawing which shows the structure of the electronic cassette which can be opened and closed which concerns on another form. It is a perspective view which shows the structure of the reversible electronic cassette which concerns on another form. It is a perspective view which shows the structure of the reversible electronic cassette which concerns on another form. It is sectional drawing which shows the structure of the electronic cassette which can be reversed which concerns on another form. It is sectional drawing which shows an example of a structure of the radiation detector which concerns on embodiment. It is a graph which shows the light emission characteristic of CsI (Tl), and the absorption wavelength range of quinacridone. It is the schematic enlarged view which expanded the columnar crystal and sensor part of a radiation detector. It is a graph which shows an example of the sensitivity characteristic of various materials. It is a graph which shows an example of the sensitivity characteristic of various materials.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
[First Embodiment]
First, the configuration of the indirect conversion radiation detector 20 according to the present embodiment will be described.

  FIG. 1 is a schematic cross-sectional view schematically showing a configuration of three pixel portions of a radiation detector 20 according to an embodiment of the present invention.

  In this radiation detector 20, a signal output unit 14, a sensor unit 13, and a scintillator 8 are sequentially stacked on an insulating substrate 1, and a pixel unit is configured by the signal output unit 14 and the sensor unit 13. . A plurality of pixel units are arranged on the substrate 1, and the signal output unit 14 and the sensor unit 13 in each pixel unit are configured to overlap each other.

  The scintillator 8 is formed on the sensor unit 13 via the transparent insulating film 7, and is formed by forming a phosphor that emits light by converting radiation incident from above (opposite side of the substrate 1) into light. It is. Providing such a scintillator 8 absorbs the radiation transmitted through the subject and emits light.

  The wavelength range of light emitted by the scintillator 8 is preferably a visible light range (wavelength 360 nm to 830 nm), and in order to enable monochrome imaging by the radiation detector 20, the wavelength range of green is included. Is more preferable.

  Specifically, as a phosphor used for the scintillator 8, when imaging using X-rays as radiation, those containing cesium iodide (CsI) are preferable, and an emission spectrum at the time of X-ray irradiation is, for example, 420 nm to It is particularly preferred to use CsI (Tl) at 700 nm. Note that the emission peak wavelength of CsI (Tl) in the visible light region is 565 nm.

  The sensor unit 13 includes an upper electrode 6, a lower electrode 2, and a photoelectric conversion film 4 disposed between the upper and lower electrodes. The photoelectric conversion film 4 absorbs light emitted from the scintillator 8 and generates electric charges. It is composed of an organic photoelectric conversion material.

Since it is necessary for the upper electrode 6 to cause the light generated by the scintillator 8 to be incident on the photoelectric conversion film 4, it is preferable that the upper electrode 6 be made of a conductive material that is transparent at least with respect to the emission wavelength of the scintillator 8. It is preferable to use a transparent conductive oxide (TCO) having a high transmittance for visible light and a small resistance value. Although a metal thin film such as Au can be used as the upper electrode 6, TCO is preferable because it tends to increase the resistance value when it is desired to obtain a transmittance of 90% or more. For example, ITO, IZO, AZO, FTO, SnO ₂ , TiO ₂ , ZnO _{2 and the} like can be preferably used, and ITO is most preferable from the viewpoint of process simplicity, low resistance, and transparency. Note that the upper electrode 6 may have a single configuration common to all the pixel portions, or may be divided for each pixel portion.

  The photoelectric conversion film 4 includes an organic photoelectric conversion material, absorbs light emitted from the scintillator 8, and generates a charge corresponding to the absorbed light. In this way, the photoelectric conversion film 4 containing an organic photoelectric conversion material has a sharp absorption spectrum in the visible range, and electromagnetic waves other than light emitted by the scintillator 8 are hardly absorbed by the photoelectric conversion film 4. The noise generated by the radiation such as being absorbed by the photoelectric conversion film 4 can be effectively suppressed.

  The organic photoelectric conversion material constituting the photoelectric conversion film 4 is preferably such that its absorption peak wavelength is closer to the emission peak wavelength of the scintillator 8 in order to absorb light emitted by the scintillator 8 most efficiently. Ideally, the absorption peak wavelength of the organic photoelectric conversion material matches the emission peak wavelength of the scintillator 8, but if the difference between the two is small, the light emitted from the scintillator 8 can be sufficiently absorbed. . 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 8 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 in the visible region of quinacridone is 560 nm, if quinacridone is used as the organic photoelectric conversion material and CsI (Tl) is used as the material of the scintillator 8, the difference in peak wavelength can be within 5 nm. Thus, the amount of charge generated in the photoelectric conversion film 4 can be substantially maximized.

  Next, the photoelectric conversion film 4 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 may be composed of an organic layer including a pair of electrodes 2 and 6 and an organic photoelectric conversion film 4 sandwiched between the electrodes 2 and 6. it can. 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.

  The materials applicable as the organic p-type semiconductor and organic n-type semiconductor and the configuration of the photoelectric conversion film 4 are described in detail in Japanese Patent Application Laid-Open No. 2009-32854, and thus the description thereof is omitted.

  The thickness of the photoelectric conversion film 4 is preferably as large as possible in terms of absorbing light from the scintillator 8. However, when the thickness is more than a certain level, the photoelectric conversion film 4 is generated in the photoelectric conversion film 4 by a bias voltage applied from both ends of the photoelectric conversion film 4. Since electric field strength is reduced and charges cannot be collected, the thickness is preferably 30 nm to 300 nm, more preferably 50 nm to 250 nm, and particularly preferably 80 nm to 200 nm.

  In the radiation detector 20 illustrated in FIG. 1, the photoelectric conversion film 4 has a single-sheet configuration common to all pixel units, but may be divided for each pixel unit.

  The lower electrode 2 is a thin film divided for each pixel portion. The lower electrode 2 can be made of a transparent or opaque conductive material, and aluminum, silver, or the like can be suitably used.

  The thickness of the lower electrode 2 can be, for example, 30 nm or more and 300 nm or less.

  In the sensor unit 13, by applying a predetermined bias voltage between the upper electrode 6 and the lower electrode 2, one of electric charges (holes, electrons) generated in the photoelectric conversion film 4 is moved to the upper electrode 6. The other can be moved to the lower electrode 2. In the radiation detector 20 of the present embodiment, a wiring is connected to the upper electrode 6, and a bias voltage is applied to the upper electrode 6 through this wiring. In addition, the polarity of the bias voltage is determined so that electrons generated in the photoelectric conversion film 4 move to the upper electrode 6 and holes move to the lower electrode 2, but this polarity is reversed. May be.

  The sensor unit 13 constituting each pixel unit only needs to include at least the lower electrode 2, the photoelectric conversion film 4, and the upper electrode 6. In order to suppress an increase in dark current, the electron blocking film 3 and hole blocking are performed. It is preferable to provide at least one of the films 5, and it is more preferable to provide both.

  The electron blocking film 3 can be provided between the lower electrode 2 and the photoelectric conversion film 4. When a bias voltage is applied between the lower electrode 2 and the upper electrode 6, electrons are transferred from the lower electrode 2 to the photoelectric conversion film 4. It is possible to suppress the dark current from increasing due to the injection of.

  An electron donating organic material can be used for the electron blocking film 3.

  The material actually used for the electron blocking film 3 may be selected according to the material of the adjacent electrode, the material of the adjacent photoelectric conversion film 4 and the like, and 1.3 eV or more from the work function (Wf) of the material of the adjacent electrode. Those having a large electron affinity (Ea) and an Ip equivalent to or smaller than the ionization potential (Ip) of the material of the adjacent photoelectric conversion film 4 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 photoelectric conversion film 4 may be formed by further containing fullerenes or carbon nanotubes.

  The thickness of the electron blocking film 3 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, in order to surely exhibit the dark current suppressing effect and prevent a decrease in photoelectric conversion efficiency of the sensor unit 13. It is 50 nm or more and 100 nm or less.

  The hole blocking film 5 can be provided between the photoelectric conversion film 4 and the upper electrode 6. When a bias voltage is applied between the lower electrode 2 and the upper electrode 6, the hole blocking film 5 is transferred from the upper electrode 6 to the photoelectric conversion film 4. 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 5.

  The thickness of the hole blocking film 5 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, in order to surely exhibit the dark current suppressing effect and prevent a decrease in photoelectric conversion efficiency of the sensor unit 13. Is from 50 nm to 100 nm.

  The material actually used for the hole blocking film 5 may be selected according to the material of the adjacent electrode, the material of the adjacent photoelectric conversion film 4 and the like, and 1.3 eV from the work function (Wf) of the material of the adjacent electrode. As described above, it is preferable that the ionization potential (Ip) is large and that the Ea is equal to or larger than the electron affinity (Ea) of the material of the adjacent photoelectric conversion film 4. 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 addition, when a bias voltage is set so that holes move to the upper electrode 6 and electrons move to the lower electrode 2 among the charges generated in the photoelectric conversion film 4, the electron blocking film 3 and the hole blocking are set. The position of the film 5 may be reversed. Moreover, it is not necessary to provide both the electron blocking film 3 and the hole blocking film 5, and if any of them is provided, a certain dark current suppressing effect can be obtained.

  A signal output unit 14 is formed on the surface of the substrate 1 below the lower electrode 2 of each pixel unit.

  FIG. 2 schematically shows the configuration of the signal output unit 14.

  Corresponding to the lower electrode 2, a capacitor 9 that accumulates the charge transferred to the lower electrode 2, and a field effect thin film transistor (hereinafter referred to simply as “Thin Film Transistor”) that converts the charge accumulated in the capacitor 9 into an electric signal and outputs the electric signal. 10 may be formed. The region in which the capacitor 9 and the thin film transistor 10 are formed has a portion that overlaps the lower electrode 2 in a plan view. With this configuration, the signal output unit 14 and the sensor unit 13 in each pixel unit are connected to each other. There will be overlap in the thickness direction. In order to minimize the plane area of the radiation detector 20 (pixel portion), it is desirable that the region where the capacitor 9 and the thin film transistor 10 are formed is completely covered by the lower electrode 2.

  The capacitor 9 is electrically connected to the corresponding lower electrode 2 through a wiring made of a conductive material penetrating an insulating film 11 provided between the substrate 1 and the lower electrode 2. Thereby, the electric charge collected by the lower electrode 2 can be moved to the capacitor 9.

  In the thin film transistor 10, a gate electrode 15, a gate insulating film 16, and an active layer (channel layer) 17 are stacked, and a source electrode 18 and a drain electrode 19 are formed on the active layer 17 at a predetermined interval. .

  The active layer 17 can be formed of, for example, amorphous silicon, amorphous oxide, organic semiconductor material, carbon nanotube, or the like. In addition, the material which comprises the active layer 17 is not limited to these.

The amorphous oxide that can form the active layer 17 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. In addition, the amorphous oxide which can comprise the active layer 17 is not limited to these.

  Examples of the organic semiconductor material that can form the active layer 17 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.

  If the active layer 17 of the thin film transistor 10 is formed of an amorphous oxide, an organic semiconductor material, or a carbon nanotube, it will not absorb radiation such as X-rays, or even if it absorbs it, it will remain in a very small amount. Generation of noise in the portion 14 can be effectively suppressed.

  When the active layer 17 is formed of carbon nanotubes, the switching speed of the thin film transistor 10 can be increased, and the thin film transistor 10 having a low light absorption in the visible light region can be formed. Note that when the active layer 17 is formed of carbon nanotubes, the performance of the thin film transistor 10 is remarkably deteriorated only by mixing a very small amount of metallic impurities into the active layer 17. It is necessary to form by separating and extracting.

  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 substrate 1 is not limited to a substrate having high heat resistance such as a semiconductor substrate, a quartz substrate, and a glass substrate, and a flexible substrate such as plastic, aramid, or bio-nanofiber can also be used. Specifically, flexible materials such as polyesters such as polyethylene terephthalate, polybutylene phthalate, and polyethylene naphthalate, polystyrene, polycarbonate, polyethersulfone, polyarylate, polyimide, polycycloolefin, norbornene resin, and poly (chlorotrifluoroethylene). 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.

  In addition, the substrate 1 is provided with 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.

  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 substrate 1 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. The substrate 1 can be formed thinly.

  In this embodiment, the signal output unit 14, the sensor unit 13, and the transparent insulating film 7 are formed in this order on the substrate 1, and the scintillator 8 is pasted on the substrate 1 using an adhesive resin with low light absorption. Thus, the radiation detector 20 is formed. Hereinafter, the substrate 1 formed up to the transparent insulating film 7 is referred to as a TFT substrate 30.

  As shown in FIG. 3, the TFT substrate 30 includes pixels 32 including the sensor unit 13, the capacitor 9, and the thin film transistor 10 described above in a certain direction (row direction in FIG. 3) and a crossing direction with respect to the certain direction. A plurality of two-dimensional shapes are provided (in the column direction in FIG. 3).

  Further, the radiation detector 20 has a plurality of gate wirings 34 extending in a certain direction (row direction) for turning on / off each thin film transistor 10 and a crossing direction (column direction) extending in an on state. A plurality of data wirings 36 for reading out charges through the thin film transistor 10 are provided.

  The radiation detector 20 is flat and has a quadrilateral shape with four sides at the outer edge in plan view. Specifically, it is formed in a rectangular shape.

  Next, a configuration of a portable radiation imaging apparatus (hereinafter referred to as an electronic cassette) 40 that incorporates the radiation detector 20 and captures a radiation image will be described.

  FIG. 4 is a perspective view showing the configuration of the electronic cassette 40.

  The electronic cassette 40 includes a flat housing 41 made of a material that transmits radiation, and has a waterproof and airtight structure. Inside the housing 41, a radiation detector 20 that detects the radiation X that has passed through the subject from the irradiation surface side of the housing 41 that is irradiated with the radiation X, and a lead plate that absorbs back scattered radiation of the radiation X 43 are arranged in order. The case 41 has a quadrilateral imaging region 41A capable of detecting radiation in a region corresponding to the arrangement position of the radiation detector 20 on one flat surface. As shown in FIG. 5, the radiation detector 20 is disposed so that the TFT substrate 30 is on the imaging region 41A side, and is affixed to the inside of the housing 41 constituting the imaging region 41A.

  In addition, a case 42 that accommodates a cassette control unit 58 and a power supply unit 70 described later is disposed on one end side inside the housing 41 at a position that does not overlap the radiation detector 20 (outside the range of the imaging region 41A). Yes.

  FIG. 6 is a block diagram showing a main configuration of the electric system of the electronic cassette 40 according to the present exemplary embodiment.

  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. Each gate wiring 34 of the TFT substrate 30 is connected to a gate line driver 52, and each data wiring 36 of the TFT substrate 30 is connected to a signal processing unit 54.

  In addition, the housing 41 includes an image memory 56, a cassette control unit 58, and a wireless communication unit 60.

  Each thin film transistor 10 of the TFT substrate 30 is sequentially turned on in a row unit by a signal supplied from the gate line driver 52 via the gate wiring 34, and the electric charge read by the thin film transistor 10 in the on state is converted into an electric signal. The data wiring 36 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 data wiring 36, and the electric signal transmitted through the individual data wiring 36. 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 includes a microcomputer (CPU) 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 40. 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 such as a console for controlling the entire radiation imaging via the wireless communication unit 60, and can transmit and receive various types of information to and from the console.

  In addition, the electronic cassette 40 is provided with a power supply unit 70, which functions as the above-described various circuits and elements (gate line driver 52, signal processing unit 54, image memory 56, wireless communication unit 60, and cassette control unit 58). The microcomputer that operates is operated by the 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 40, and supplies power from the charged battery to various circuits and elements. In FIG. 6, wiring for connecting the power supply unit 70 to various circuits and elements is omitted.

  Next, the operation of the electronic cassette 40 according to the present embodiment will be described.

  The electronic cassette 40 according to the present embodiment, when radiographic images are taken, is arranged with the radiographing region 41A on the upper side and spaced from the radiation generating device 80 that generates radiation, as shown in FIG. A region B to be imaged by the patient is arranged on the region. The radiation generator 80 emits radiation X 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 40 after carrying image information by passing through the imaging target region B.

  The radiation X emitted from the radiation generator 80 reaches the electronic cassette 40 after passing through the imaging target region B. As a result, charges corresponding to the dose of the irradiated radiation X are generated in each sensor unit 13 of the radiation detector 20 incorporated in the electronic cassette 40, and the charges generated by the sensor unit 13 are accumulated in the capacitor 9. The

  The cassette control unit 58 controls the gate line driver 52 after the radiation X irradiation is completed, and sequentially outputs an ON signal from the gate line driver 52 to each gate wiring 34 of the radiation detector 20 to read out image information. I do. Image information read from the radiation detector 20 is stored in the image memory 56.

  Incidentally, in the electronic cassette 40 according to the present embodiment, as shown in FIG. 5, the radiation detector 20 is incorporated so that the radiation X is irradiated from the TFT substrate 30 side.

  Here, as shown in FIG. 7, the radiation detector 20 is irradiated with radiation X from the front side on which the scintillator 8 is formed (“front surface irradiation”, “back surface reading method” (so-called PSS (Penetration Side Sampling) method)). In this case, light is emitted more strongly on the upper surface side (opposite side of the TFT substrate 30) of the scintillator 8, and radiation X is irradiated from the TFT substrate 30 side (rear side) ("back surface irradiation", "front surface reading method" ( The so-called ISS (Irradiation Side Sampling) method)). ), The radiation X transmitted through the TFT substrate 30 enters the scintillator 8, and the TFT substrate 30 side of the scintillator 8 emits light more strongly. Electric charges are generated in each sensor unit 13 provided on the TFT substrate 30 by light generated by the scintillator 8. For this reason, since the radiation detector 20 has a light emission position of the scintillator 8 with respect to the TFT substrate 30 when the radiation X is irradiated from the back side, compared with the case where the radiation X is irradiated from the front side, the radiation obtained by imaging High image resolution.

  In the radiation detector 20, the photoelectric conversion film 4 is made of an organic photoelectric conversion material, and the photoelectric conversion film 4 hardly absorbs radiation. For this reason, the radiation detector 20 according to the present embodiment suppresses a decrease in sensitivity to the radiation X because the amount of radiation absorbed by the photoelectric conversion film 4 is small even when the radiation is transmitted through the TFT substrate 30 by backside illumination. Can do. In the backside irradiation, the radiation passes through the TFT substrate 30 and reaches the scintillator 8. In this way, when the photoelectric conversion film 4 of the TFT substrate 30 is composed of an organic photoelectric conversion material, the radiation of the photoelectric conversion film 4 is irradiated. Since there is almost no absorption and radiation attenuation can be suppressed to a low level, it is suitable for backside illumination.

  In addition, both the amorphous oxide constituting the active layer 17 of the thin film transistor 10 and the organic photoelectric conversion material constituting the photoelectric conversion film 4 can be formed at a low temperature. For this reason, the board | substrate 1 can be formed with a plastic resin, aramid, and bio-nanofiber with little radiation absorption. Since the substrate 1 formed in this way has a small amount of radiation absorption, a decrease in sensitivity to the radiation X can be suppressed even when the radiation is transmitted through the TFT substrate 30 by backside illumination.

  Further, according to the present embodiment, as shown in FIG. 5, the radiation detector 20 is attached to the imaging region 41A portion in the housing 41 so that the TFT substrate 30 is on the imaging region 41A side. When the substrate 1 is formed of a highly rigid plastic resin, aramid, or bionanofiber, the radiation detector 20 itself has high rigidity, so that the imaging region 41A portion of the housing 41 can be formed thin. In addition, when the substrate 1 is formed of a highly rigid plastic resin, aramid, or bionanofiber, the radiation detector 20 itself has flexibility, so that even when an impact is applied to the imaging region 41A, the radiation detector 20 is damaged. It ’s hard.

  In addition, after forming the scintillator 8 on the support, the radiation detector 20 is obtained by arranging the scintillator 8 on the TFT substrate 30. However, the method of superimposing the scintillator 8 and the TFT substrate 30 is not particularly limited. It is sufficient that both are optically coupled. As a method of arranging both of them in a superimposed manner, either a method of directly adhering them to each other or a method of adhering them via some adhesive layer or planarization layer may be used.

  For example, as shown in FIG. 27, as the scintillator 8, for example, a columnar crystal of CsI (Tl) is formed on the vapor deposition substrate 250 by vapor deposition, and the photoelectric conversion film 4 of each sensor unit 13 of the TFT substrate 30 is quinacridone. When the radiation detector 20 is formed by bonding the scintillator 8 and the TFT substrate 30 so that the surface side on which the columnar crystals are formed faces the TFT substrate 30, the MTF (modulation transfer) of the radiation image obtained by imaging is formed. function) characteristics can be improved.

  As shown in FIG. 28, CsI (Tl) has an emission peak wavelength of 565 nm, but the emitted light includes light in a wide wavelength range (400 nm to 700 nm). On the other hand, quinacridone has sensitivity to light in the wavelength range of 430 nm to 620 nm.

  Further, when the scintillator 8 is a columnar crystal of CsI (Tl), light is generated in each columnar crystal when irradiated with radiation. As shown in FIG. 29, when the light generated in the columnar crystal 252 exceeds the critical angle (for example, 34 °) at which the incident angle θ incident on the interface 254 with the outside of the columnar crystal 252 is totally reflected, If it is totally reflected in the columnar crystal 252 and is within the critical angle, a part is transmitted to the outside. For this reason, as shown in FIG. 29, the light transmitted through the columnar crystal 252A may enter the adjacent columnar crystal 252B. The transmitted light is refracted at the interface 254 and changes its traveling direction. The angle 1 incident on the interface 254 of the light transmitted through the columnar crystal 252A and the angle 2 output from the interface 254, and the angle 3 of the transmitted light exiting from the interface 254 of the adjacent columnar crystal 252B include an angle 1> Angle 2 <Angle 3 Further, the change in the angle 3 with respect to the angle 1 in the traveling direction due to refraction is larger for light having a shorter wavelength and smaller for light having a longer wavelength. The light transmitted to the columnar crystal 252B has a higher probability of being transmitted again without being totally reflected at the interface 254 of the columnar crystal 254B because the angle change due to refraction is smaller as the wavelength is longer, and as a result, light having a longer wavelength is transmitted. A phenomenon in which light reaches a position far away and light enters the sensor unit 13 of another pixel 32 is likely to occur. Note that FIG. 29 shows a case where the filling rate of the columnar crystals 252 is high (for example, 80%). Since the interval T between the columnar crystals 252 is short, the light path between the columnar crystals 252 is related to the wavelength. Are considered identical.

  However, when the photoelectric conversion film 4 is formed of quinacridone, the ray detector 20 can reduce the sensitivity of each sensor unit 13 with respect to light having a long wavelength that easily reaches the other pixels 32, thereby improving the MTF characteristics. be able to.

  In particular, in a radiation imaging apparatus for breasts (so-called mammography) that captures a radiation image of a breast of a subject, it is required to clearly capture a minute part such as a minute calcification part, and the pixel 32 of the radiation detector 20 is required. Is also formed in high definition with a small size. In the radiation detector 20, when the pixels 32 are formed with high definition, the distance between the pixels is also reduced, and each pixel 32 is easily affected by light from the other pixels 32. For this reason, in the radiation detector 20 used in the radiation imaging apparatus for breasts, the scintillator 8 is formed of a columnar crystal of CsI (Tl), and the photoelectric conversion film 4 of each sensor unit 13 of the TFT substrate 30 is formed of quinacridone. This is effective for taking clear radiographic images.

[Second Embodiment]
Next, a second embodiment will be described. In addition, the same code | symbol is attached | subjected to the part same as 1st Embodiment, description is abbreviate | omitted, and only a different part is demonstrated.

  First, the configuration of the imaging unit 21 that captures a radiographic image will be described.

  The imaging unit 21 according to the present embodiment has two imaging systems that capture radiographic images indicated by the irradiated radiation, and can individually read image information indicating the radiographic images captured by each imaging system It is configured as follows.

  Specifically, as shown in FIG. 8, the two radiation detectors 20 (20A, 20B) are arranged so that the scintillator 8 side faces each other with a light shielding plate 27 that transmits radiation and shields light. . Hereinafter, when the scintillator 8 and the TFT substrate 30 of the two radiation detectors 20A and 20B are distinguished from each other, the scintillator 8 and the TFT substrate 30 of the radiation detector 20A are denoted by the symbol A, and the scintillator 8 and the TFT substrate of the radiation detector 20B are attached. Reference numeral 30 is attached to the reference numeral 30 for explanation.

  In this way, by providing the scintillator 8A and the TFT substrate 30A in order on one surface of the light shielding plate 27, the radiation detector 20A is irradiated with radiation from one surface side, and the other side of the light shielding plate 27 is irradiated. By providing the scintillator 8B and the TFT substrate 30B in this order on the surface, the radiation detector 20B is irradiated with radiation from the other surface side. Further, by providing the light shielding plate 27 between the two radiation detectors 20A and 20B, the light generated by the scintillator 8A does not pass to the scintillator 8B side, and the light generated by the scintillator 8B does not pass to the scintillator 8A side. .

  Here, the light emission characteristics of the scintillator 8 change depending on the thickness. As the thickness increases, the amount of light emission increases and the sensitivity increases, but the image quality deteriorates due to light scattering or the like.

  Further, for example, when the scintillator 8 is formed by filling particles that emit light when irradiated with radiation such as GOS, the larger the particle size, the greater the amount of light emission and the higher the sensitivity, but the light scattering is increased. Since it increases and affects adjacent pixels, the image quality deteriorates.

  The scintillator 8 can have a multilayer structure of small particles and large particles. For example, as shown in FIG. 9, the scintillator 8 emits small particles in a radial manner although the image side is less blurred when the irradiation side is the small particle region 8A and the TFT substrate 30 side is the large particle region 8B. The oblique component of light does not reach the TFT substrate 30 and the sensitivity is lowered. In addition, the sensitivity is increased by changing the ratio of the region 8A and the region 8B and increasing the large particle layer to the small particle layer, but the image quality deteriorates because light scattering affects the adjacent pixels. To do.

  Further, the scintillator 8 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 the scintillator 8 particles by the volume of the scintillator 8 × 100. In addition, since the scintillator 8 handles powder and it is difficult to manufacture when the filling rate exceeds 80%, the filling rate is preferably 50 to 80% by volume.

  In addition, the scintillator 8 has a light emission characteristic that changes depending on the doping amount of the activator, and the light emission amount tends to increase as the doping amount of the activator increases, but the light scattering increases and the image quality deteriorates.

  Further, the scintillator 8 has different emission characteristics with respect to radiation by changing the material used.

  For example, when the scintillator 8A is formed of GOS and the scintillator 8B is formed of CsI (Tl), the scintillator 8A is focused on sensitivity, and the scintillator 8B is focused on image quality.

  Further, the scintillator 8 has a light emission characteristic with respect to radiation by adopting a layer structure having a flat plate shape or a columnar separation.

  For example, when the scintillator 8A has a flat layer structure and the scintillator 8B has a columnar separation layer structure, the scintillator 8A is focused on sensitivity and the scintillator 8B is focused on image quality.

  In addition, as shown in FIG. 10, by forming a reflective layer 29 that transmits X-rays and reflects visible light on the surface of the scintillator 8 opposite to the TFT substrate 30, the generated light is more efficiently converted into TFTs. Since it can be led to the substrate 30, 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 made of a material having high reflection in the light emission wavelength region of the scintillator 8 to be used, such as Au, Ag, Cu, Al, Ni, and Ti. For example, when the scintillator 8 is GOS: Tb, Ag, Al, Cu or the like having a high reflectance at a wavelength of 400 to 600 nm is preferable, and the reflectance is not obtained when the thickness is less than 0.01 μm, and the thickness exceeds 3 μm. However, 0.01 to 3 μm is preferable because a further effect cannot be obtained by improving the reflectance.

  Here, the scintillator 8 has characteristics by changing the particle size, particle multi-layer structure, particle filling rate, activator dope, material, layer structure, and the formation of the reflective layer 29 in combination. It goes without saying that can be different.

  Also, the TFT substrates 30A and 30B can be made by changing the material of the photoelectric conversion film 4, or forming a filter between the TFT substrate 30A and the scintillator 8A, between the TFT substrate 30B and the scintillator 8B, or the TFT substrate 30A and the TFT. The light receiving area of the sensor unit 13 is changed with the substrate 30B 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 30A and the TFT substrate 30B. The light receiving characteristics with respect to the light of the TFT substrates 30A and 30B can be changed by making them narrower than those on the side that emphasizes sensitivity, or by changing the signal reading characteristics of the TFT substrates 30A and 30B.

  In the present embodiment, the thickness of the scintillators 8A, 8B, the particle diameter, the particle multilayer structure, the particle filling rate, the activator dope amount, the material, the layer structure are changed, or the reflective layer 29 is formed. Alternatively, a filter is formed between the TFT substrate 30A and the scintillator 8, or between the TFT substrate 30B and the scintillator 8, or the light receiving area of the sensor unit 13 is changed between the TFT substrate 30A and the TFT substrate 30B. By making the side more important than the side focusing on image quality, or by changing the pixel pitch between the TFT substrate 30A and the TFT substrate 30B and making the pixel pitch narrower than the side focusing on sensitivity on the side focusing on image quality, The characteristics of the radiographic images taken by the detectors 20A and 20B are made different.

  Specifically, the radiation detector 20A is focused on image quality, and the radiation detector 20B is focused on sensitivity.

  Next, the configuration of the electronic cassette 40 incorporating such a photographing unit 21 will be described.

  FIG. 11 is a perspective view showing the configuration of the electronic cassette 40, and FIG. 12 is a sectional view of the electronic cassette 40.

  In the electronic cassette 40, the above-described photographing unit 21 is disposed inside a housing 41. In the case 41, areas corresponding to the positions where the imaging unit 21 is provided on one surface of the flat plate and the other surface are imaging areas 41A and 41B that are irradiated with radiation during imaging. As shown in FIG. 12, the imaging unit 21 is built in the housing 41 so that the radiation detector 20A is on the imaging region 41A side with the light shielding plate 27 interposed therebetween, and the imaging region 41A emphasizes image quality. The shooting area and the shooting area 41B are set as sensitivity-oriented shooting areas.

  FIG. 13 is a block diagram showing a main configuration of the electric system of the electronic cassette 40 according to the present exemplary embodiment.

  In each of the radiation detectors 20A and 20B, 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. Hereinafter, when the gate line driver 52 and the signal processing unit 54 provided corresponding to the two radiation detectors 20A and 20B are distinguished from each other, the gate line driver 52 and the signal processing unit 54 corresponding to the radiation detector 20A are denoted by the symbol A. The gate line driver 52 and the signal processing unit 54 corresponding to the radiation detector 20B will be described with reference B.

  Each gate wiring 34 of the TFT substrate 30A is connected to the gate line driver 52A, each data wiring 36 of the TFT substrate 30A is connected to the signal processing unit 54A, and each gate wiring 34 of the TFT substrate 30B is a gate line. Connected to the driver 52B, each data wiring 36 of the TFT substrate 30B is connected to the signal processing unit 54B.

  The thin film transistors 10 on the TFT substrates 30A and 30B are sequentially turned on in units of rows by signals supplied from the gate line drivers 52A and 52B via the gate wiring 34, and the electric charges read by the thin film transistors 10 that are turned on are The data wiring 36 is transmitted as an electrical signal and input to the signal processing units 54A and 54B. As a result, the charges are sequentially read out in units of rows, and a two-dimensional radiation image can be acquired.

  An image memory 56 is connected to the signal processing units 54A and 54B, and image data output from the A / D converters of the signal processing units 54A and 54B are stored in the image memory 56 in order.

  The cassette control unit 58 individually controls the operation of the gate line drivers 52A and 52B, and can individually control reading of image information indicating a radiation image from the TFT substrates 30A and 30B.

  Next, the operation of the electronic cassette 40 according to the present embodiment will be described.

  The electronic cassette 40 according to the present embodiment is capable of imaging with only one of the radiation detectors 20A and 20B and imaging with both of the radiation detectors 20A and 20B when imaging a radiographic image. .

  In addition, when the radiation detectors 20A and 20B are both photographed, it is possible to generate an energy subtraction image by performing image processing that weights and adds the radiation images photographed by the radiation detectors 20A and 20B for each corresponding pixel. Has been.

  The electronic cassette 40 is provided with an imaging area 41A emphasizing image quality and an imaging area 41B emphasizing sensitivity, and by inverting the whole, radiographic images can be captured in the imaging area 41A or the imaging area 41B.

  The electronic cassette 40 generates radiation as shown in FIG. 12 with the imaging region 41A facing up when capturing image quality and energy subtraction images, and with the capturing region 41B facing up when capturing with sensitivity. The radiation generator 80 is arranged at a distance from each other, and the imaging target region B of the patient is arranged on the imaging region. 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 40 after carrying image information by passing through the imaging target region B.

  The radiation X emitted from the radiation generator 80 reaches the electronic cassette 40 after passing through the imaging target region B. As a result, charges corresponding to the dose of the irradiated radiation X are generated in each sensor unit 13 of the radiation detector 20 incorporated in the electronic cassette 40, and the charges generated by the sensor unit 13 are accumulated in the capacitor 9. The

  The cassette control unit 58 controls the operation of the gate line drivers 52A and 52B, and wirelessly communicates shooting condition information indicating whether to focus on image quality, sensitivity, or energy subtraction images from the console at the time of shooting. Receive via the unit 60. Then, the cassette control unit 58 reads the image by controlling the gate line drivers 52A and 52B according to the imaging condition information after the irradiation of the radiation X is completed.

  As described above, the electronic cassette 40 can easily capture radiographic images having different characteristics by inverting the main body and performing imaging in the imaging region 41A or the imaging region 41B. The electronic cassette 40 can also take an energy subtraction image.

  In addition, as shown in FIG. 12, in the electronic cassette 40 according to the present embodiment, the radiation detector 20A performs back-surface irradiation with respect to the imaging region 41A, and the radiation detector 20B performs back-surface irradiation with respect to the imaging region 41B. However, since the amount of radiation absorbed by the substrate 1 is small even when passing through the TFT substrate 30, it is possible to suppress a decrease in sensitivity to the radiation X.

  As mentioned above, although this invention was demonstrated using each embodiment, the technical scope of this invention is not limited to the range as described in each 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.

  In addition, each of the above embodiments does not limit the invention according to the claims (claims), and all combinations of features described in each embodiment are indispensable for solving means of the invention. Not always. Each embodiment described above includes 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 present invention is applied to the electronic cassette 40 which is a portable radiographic imaging apparatus has been described. However, the present invention is not limited to this and is applied to a stationary radiographic imaging apparatus. May be.

  In each of the above embodiments, the case where one scintillator 8 is provided on the TFT substrate 30 has been described. However, the present invention is not limited to this. For example, as shown in FIG. 14, a plurality (two in FIG. 14) of scintillators 8 (8A, 8B) may be provided on the TFT substrate 30. Further, since sensitivity and image characteristics change depending on the thickness of the scintillator 8, as shown in FIG. 15, a light-transmitting bag body 202 is disposed so as to face the detection region of the radiation detector 20, and the liquid scintillator. The liquid scintillator is injected into the bag body 202 by the pump 204 from the tank 206 in which the liquid is stored, and the liquid scintillator injected into the bag body 202 is taken out, and the amount of liquid scintillator stored in the bag body 202 is reduced. You may change the thickness of the bag body 202 by changing. Thereby, the sensitivity and image characteristics of the radiographic image to be taken can be changed. It should be noted that the bag body 202 is disposed on the TFT substrate 30 instead of the scintillator 8 so that the liquid scintillator is injected into the bag body 202 by the pump 204 and the liquid scintillator injected into the bag body 202 is taken out. Good. By filling or removing the liquid scintillator with the pump 204, the TFT substrate 30 can be brought into close contact with or separated from the TFT substrate 30. For example, when the TFT substrate 30 is deteriorated by radiation, only the TFT substrate 30 can be replaced.

  In the first embodiment, the case where the cassette control unit 58 and the power supply unit 70 are arranged in the casing 41 of the electronic cassette 40 so as not to overlap the case 42 and the radiation detector 20 has been described. However, the present invention is not limited to this. For example, the radiation detector 20 and the cassette control unit 58 or the power supply unit 70 may be arranged so as to overlap each other.

  Moreover, although each said embodiment demonstrated the case where the electronic cassette 40 was formed in flat rectangular shape and substantially constant thickness, it is not limited to this. For example, as shown in FIG. 16, the imaging unit 40A in which the radiation detector 20 is built may be formed thinner than the control unit 40B in which the cassette control unit 58 and the power supply unit 70 are arranged.

  In the second embodiment, the imaging unit 21 is described as having a configuration in which the two radiation detectors 20A and 20B are arranged so that the scintillator 8 faces each other with the light shielding plate 27 interposed therebetween. It is not limited to. For example, as shown in FIG. 17, the TFT substrate 30A may be disposed on one surface of one scintillator 8, and the TFT substrate 30B may be disposed on the other surface of the scintillator 8. Further, when the radiation detectors 20A and 20B are less influenced by the light of the other scintillator 8, as shown in FIG. 18, the radiation detectors 20A and 20B are mutually connected to the scintillators 8A and 8B without providing the light shielding plate 27. It is good also as a structure arrange | positioned so that may face. If the electronic cassette 40 is to capture an energy subtraction image, the radiation detectors 20A and 20B are stacked so that the radiation X is irradiated with the back surface of the radiation X with the light shielding plate 27 interposed therebetween as shown in FIG. Alternatively, as shown in FIG. 20, the radiation detectors 20 </ b> A and 20 </ b> B may be stacked so as to be irradiated with the back surface with respect to the radiation X without providing the light shielding plate 27.

  Further, in the second embodiment, the electronic cassette 40 can be imaged on both sides of the imaging region 41A or the imaging region 41B by inverting the whole, but the electronic cassette as shown in FIGS. Examples are a configuration in which the electronic cassette 40 can be opened and closed, and a configuration in which a part of the electronic cassette 40 as shown in FIGS.

  21 and 22 are perspective views showing other configurations of the electronic cassette 40, and FIG. 23 is a cross-sectional view showing a schematic configuration of the electronic cassette 40. In addition, the same code | symbol is attached | subjected about the part corresponding to the electronic cassette 40 of 2nd Embodiment, and description is abbreviate | omitted about the part which has the same function.

  The electronic cassette 40 includes the above-described imaging unit 21, gate line drivers 52A and 52B, signal processing units 54A and 54B, and the like, and includes a flat imaging unit 90 that captures a radiographic image of irradiated radiation, and the above-described cassette. A control unit 58 and a control unit 92 having a built-in power supply unit 70 are connected by a hinge 94 so as to be opened and closed.

  The photographing unit 90 and the control unit 92 are rotated with the hinge 94 as a rotation center with respect to the other, whereby the photographing unit 90 and the control unit 92 are arranged in an unfolded state (FIG. 22). And the control unit 92 can be opened and closed in a folded state (FIG. 21).

  As shown in FIG. 23, the imaging unit 90 includes the imaging unit 21 so that the radiation detector 20B is on the control unit 92 side and the radiation detector 20A is on the outside (opposite side of the control unit 92 side). In the retracted state, the surface side that is on the outer side is an imaging region 41B that emphasizes sensitivity, and the surface side that faces the control unit 92 is an imaging region 41A that emphasizes image quality.

  The imaging unit 21 and the cassette control unit 58 and the power supply unit 70 are connected by a connection wiring 96 provided in the hinge 94.

  As described above, the electronic cassette 40 can be easily opened and closed to perform imaging in the imaging region 41A or the imaging region 41B, thereby easily capturing radiographic images having different characteristics.

  24 and 25 are perspective views showing other configurations of the electronic cassette 40 according to the embodiment, and FIG. 26 is a cross-sectional view showing a schematic configuration of the electronic cassette 40. . In addition, the same code | symbol is attached | subjected about the part corresponding to the electronic cassette 40 of 2nd Embodiment, and description is abbreviate | omitted about the part which has the same function.

  The electronic cassette 40 includes the above-described imaging unit 21, gate line drivers 52A and 52B, and signal processing units 54A and 54B, and includes a flat imaging unit 90 that captures a radiographic image of irradiated radiation, and the above-described cassette control. The unit 58 and the control unit 92 in which the power source unit 70 is built up are rotatably connected by a rotating shaft 98.

  In addition, the photographing unit 90 is provided with photographing regions 41A and 41B on one surface and the other surface of the flat plate corresponding to the arrangement position of the photographing unit 21.

  The imaging unit 21 is built in such that the radiation detector 20B is on the imaging area 41B side, and the radiation detector 20A is on the imaging area 41A. The imaging area 41B is an imaging area that emphasizes sensitivity, and the imaging area 41A is an image quality. It is regarded as an important shooting area.

  The imaging unit 21, the cassette control unit 58, and the power supply unit 70 are connected by a connection wiring 96 provided in the rotation shaft 98.

  In the photographing unit 90 and the control unit 92, when the other rotates, the photographing region 41A and the operation panel 99 are arranged (FIG. 24), and the photographing region 41B and the operation panel 99 are arranged. It can be changed to (FIG. 25).

  As described above, the electronic cassette 40 can be easily rotated to capture radiographic images having different characteristics by performing imaging in the imaging region 41A or the imaging region 41B.

  Further, as the sensor unit 13 of the radiation detector 20, an organic CMOS sensor in which the photoelectric conversion film 4 is made of a material containing an organic photoelectric conversion material may be used. As the TFT substrate 30 of the radiation detector 20, the thin film transistor 10. An organic TFT array sheet in which organic transistors including the organic material are arranged in an array on a flexible sheet may be used. Said organic CMOS sensor is disclosed by Unexamined-Japanese-Patent No. 2009-212377, for example. In addition, the organic TFT array sheet described above is, for example, “Nihon Keizai Shimbun,“ The University of Tokyo, “Developing“ Ultra Flexible ”Organic Transistor” ”, [online], [Search May 8, 2011], Internet <URL : Http://www.nikkei.com/tech/trend/article/g=96958A9C93819499E2EAE2E0E48DE2EAE3E3E0E2E3E2E2E2E2E2E2E2; p = 9694E0E7E2E6E0E2E3E2E2E0E2E0> ”

  When a CMOS sensor is used as the sensor unit 13 of the radiation detector 20, the advantage that photoelectric conversion can be performed at a high speed and the result that the substrate can be thinned can suppress radiation absorption when the ISS method is adopted. There is an advantage that it can be suitably applied to mammography photography.

  On the other hand, when using a CMOS sensor as the sensor unit 13 of the radiation detector 20, there is a low resistance to radiation when a crystalline silicon substrate is used. For this reason, conventionally, there has been a technique for taking measures such as providing an FOP (fiber optical plate) between the sensor unit and the TFT substrate.

  Based on this drawback, a technique using a SiC (silicon carbide) substrate as a semiconductor substrate having high resistance to radiation can be applied. Advantages that can be used as an ISS method by using a SiC substrate, and because SiC has a lower internal resistance and a smaller amount of heat generation than Si, it suppresses the amount of heat generation when shooting movies, and raises the temperature of CsI There is an advantage that it is possible to suppress a decrease in sensitivity due to.

  Thus, a substrate having high resistance to radiation, such as a SiC substrate, is generally a wide cap (about 3 eV), and as an example, as shown in FIG. 30, the absorption edge is about 440 nm corresponding to the blue region. Therefore, in this case, a scintillator such as CsI: Tl or GOS that emits light in the green region cannot be used.

  On the other hand, since the research on scintillators that emit light in these green regions has been actively conducted from the sensitivity characteristics of amorphous silicon, there is a high demand for using the scintillators. For this reason, the scintillator which light-emits in a green area | region can be used by comprising the photoelectric converting film 4 with the material containing the organic photoelectric conversion material which absorbs light emission in a green area | region.

  When the photoelectric conversion film 4 is formed of a material containing an organic photoelectric conversion material and the thin film transistor 10 is formed using a SiC substrate, the photoelectric conversion film 4 and the thin film transistor 10 have different sensitivity wavelength regions, and thus the light emitted by the scintillator is emitted. There is no noise of the thin film transistor 10.

  Further, if SiC and a material containing an organic photoelectric conversion material are laminated as the photoelectric conversion film 4, in addition to receiving light emission mainly in the blue region, such as CsI: Na, light emission in the green region is also received. As a result, the sensitivity can be improved. In addition, since the organic photoelectric conversion material hardly absorbs radiation, it can be suitably used for the ISS system.

  Note that SiC is highly resistant to radiation because it is difficult for nuclear nuclei to be blown away even when exposed to radiation. Develop semiconductor devices that can be used for a long time ", [online], [Search May 8, 2011], Internet <URL: http://www.jaea.go.jp/jari/jpn/publish/01/ff/ ff36 / sic.html> ”.

  Moreover, C (diamond), BN, GaN, AlN, ZnO etc. are mentioned as a semiconductor material with high tolerance with respect to radiation other than SiC. These light element semiconductor materials have high radiation resistance because they are mainly wide-gap semiconductors, so they require high energy for ionization (electron-hole pair formation), small reaction cross sections, and This is due to the fact that bonding is strong and atomic displacement is less likely to occur. Regarding this point, for example, “Electronics Research Institute,“ New Development of Nuclear Electronics ”, [online], [Search May 8, 2011], Internet <URL: http: //www.aist .go.jp / ETL / jp / results / bulletin / pdf / 62-10to11 / kobayashi150.pdf> and “Research on Radiation Resistance of Zinc Oxide Electronic Devices”, 2009 Wakasa Bay Energy This is disclosed in “Research Center Open Joint Research Report, March 2010”. Regarding the radiation resistance of GaN, for example, “Tohoku University,“ Evaluation of radiation resistance of gallium nitride device ”, [online], [Search May 8, 2011], Internet <URL: http: // cycgw1 .cyric.tohoku.ac.jp / ~ sakemi / ws2007 / ws / pdf / narita.pdf> ”.

  In addition, since GaN has good thermal conductivity for applications other than blue LEDs and has high insulation resistance, ICs have been studied in the field of power systems. Further, ZnO has been studied for LEDs that emit light mainly in the blue to ultraviolet region.

By the way, when SiC is used, the band gap Eg is changed from about 1.1 eV to about 2.8 eV of Si, so that the light absorption wavelength λ shifts to the short wavelength side. Specifically, since the wavelength λ = 1.24 / Eg × 1000, the sensitivity changes to wavelengths up to about 440 nm. Therefore, when SiC is used, as shown in FIG. 31 as an example, the scintillator emits light in the blue region rather than CsI: Tl (peak wavelength: about 565 nm) that emits light in the green region. This is more suitable as the emission wavelength. Since the phosphor emits blue light well, CsI: Na (peak wavelength: about 420 nm), BaFX: Eu (X is a halogen such as Br and I, peak wavelength: about 380 nm), CaWO ₄ (peak wavelength: about 425 nm) ZnS: Ag (peak wavelength: about 450 nm), LaOBr: Tb, Y ₂ O ₂ S: Tb, and the like are suitable. In particular, BaFX: Eu used in CsI: Na and CR cassettes, and CaWO ₄ used in screens and films are preferably used.

On the other hand, as a CMOS sensor having high resistance to radiation, a CMOS sensor may be configured by using a configuration of Si substrate / thick film SiO ₂ / organic photoelectric conversion material by SOI (Silicon On Insulator).

  Technologies that can be applied to this configuration include, for example, “Japan Aerospace Exploration Agency (JAXA) Institute for Space Science,“ High radiation resistance by combining the most advanced consumer SOI technology and radiation resistance technology for space. “Development of functional logic integrated circuit development platform for the first time in the world”, [online], [Search May 8, 2011], Internet <URL: http://www.jaxa.jp/press/2010/11/20101122_soi_j .html> ".

  In SOI, since the radiation tolerance of the film thickness SOI is high, examples of the high radiation durability element include a complete separation type thick film SOI and a partial separation type thick film SOI. As for these SOIs, for example, “Patent Office,“ Patent Application Technology Trend Survey Report on SOI (Silicon On Insulator) Technology ”, [online], [Search May 8, 2011], Internet <URL: http://www.jpo.go.jp/shiryou/pdf/gidou-houkoku/soi.pdf> ”.

  Further, even if the thin film transistor 10 or the like of the radiation detector 20 does not have light transmission (for example, a structure in which the active layer 17 is formed of a material having no light transmission such as amorphous silicon), the thin film transistor 10 or the like. Is disposed on a light-transmitting substrate 1 (for example, a flexible substrate made of synthetic resin), and a portion of the substrate 1 where the thin film transistor 10 or the like is not formed is configured to transmit light. It is possible to obtain a radiation detector 20 having optical transparency. Arranging the thin film transistor 10 or the like having a non-light-transmitting structure on the light-transmitting substrate 1 is performed by separating the micro device block manufactured on the first substrate from the first substrate. This can be realized by applying the technology arranged above, specifically, for example, FSA (Fluidic Self-Assembly). The above FSA is, for example, “Toyama University,“ Study on Self-Aligned Placement Technology of Small Semiconductor Blocks ”, [online], [Search May 8, 2011], Internet <URL: http: //www3.u- toyama.ac.jp/maezawa/Research/FSA.html> ”.

8, 8A, 8B Scintillator (light emitting layer)
DESCRIPTION OF SYMBOLS 10 Thin-film transistor 13 Sensor part 20, 20A, 20B Radiation detector 30, 30A, 30B TFT substrate (board | substrate)
40 Electronic cassette 41 Housing 202 Bag body 204 Pump (actuator)
206 tanks

An object of the present invention is to provide a radiation imaging apparatus that can easily capture radiation images having different characteristics .

In order to achieve the above object, a radiographic apparatus according to the present invention includes a light emitting layer that generates light when irradiated with radiation, and a substrate provided with a plurality of sensor portions that generate electric charges when receiving light. The two radiation detectors are arranged so as to overlap each other in the direction in which the radiation is incident, and the light emitting layers of the two radiation detectors each have emission characteristics with respect to the radiation. In contrast, it is possible to take a radiographic image of the irradiated radiation on either one side or the other side.

According to the present invention, two radiation detectors in which a light emitting layer that generates light when irradiated with radiation and a substrate on which a plurality of sensor units that generate charges when receiving light are provided are stacked. Are arranged so as to be overlapped with respect to the incident direction of radiation.

The light emitting layers of the two radiation detectors have different emission characteristics with respect to the radiation, and radiation images of the irradiated radiation can be taken on either one side or the other side.

As described above, according to the present invention, the light emitting layers of the two radiation detectors arranged so as to overlap with each other in the radiation incident direction have different light emission characteristics with respect to the radiation, and one surface side and the other surface. It is possible to take a radiographic image of the irradiated radiation on either side. For this reason, according to the present invention, radiographic images having different characteristics can be easily captured.

The present invention may further include a light shielding member that transmits radiation and shields light between the two radiation detectors.

In the present invention, the light emitting layer of one radiation detector may be configured to include CsI, and the light emitting layer of the other radiation detector may be configured to include GOS.

In the present invention, the light emitting layer of the radiation detector disposed on the radiation incident side may be configured to include CsI.

In the present invention, the sensor unit of one radiation detector and the sensor unit of the other radiation detector may have different light receiving areas.

In addition, the present invention may further include a control unit that performs control to generate an energy subtraction image using radiographic images captured by two radiation detectors.

The present invention also provides an imaging unit including two radiation detectors, a control unit including a control unit, a deployed state where the imaging unit and the control unit are arranged, and the imaging unit and the control unit overlap each other. And a connecting member that connects the photographing unit and the control unit so as to be able to be opened and closed in the folded state.

In addition, the present invention provides an imaging unit including two radiation detectors, a control unit including a controller, and imaging so that one surface of the imaging unit and the other surface can be reversed with respect to the control unit. You may further provide the connection member connected with a unit and a control unit.

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

Electromagnetic wave absorption / photoelectric conversion part in the radiation detector 20 according to the present invention includes an electrode 2,6 of a pair, it is constituted by an organic layer containing a photoelectric conversion layer 4 sandwiched between the electrodes 2 and 6 it can. 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.

Further, according to the present embodiment, as shown in FIG. 5, the radiation detector 20 is attached to the imaging region 41A portion in the housing 41 so that the TFT substrate 30 is on the imaging region 41A side. When the substrate 1 is formed of a highly rigid plastic resin, aramid, or bionanofiber, the radiation detector 20 itself has a high rigidity, so that the imaging region 41A portion of the housing 41 can be formed thin. In addition, when the substrate 1 is formed of a highly rigid plastic resin, aramid, or bionanofiber, the radiation detector 20 itself has flexibility, so that even when an impact is applied to the imaging region 41A, the radiation detector 20 is damaged. It ’s hard.

In each of the above embodiments, the case where one scintillator 8 is provided on the TFT substrate 30 has been described. However, the present invention is not limited to this. For example, as shown in FIG. 14, a plurality (two in FIG. 14) of scintillators 8 (8A, 8B) may be provided on the TFT substrate 30. Further, since the thickness of the thus sensitivity and image characteristics of the scintillator 8 is changed, as shown in FIG. 15, so as to face the detection area of the radiation detector 20, to place the bag 202 having optical transparency, a liquid The liquid scintillator is injected into the bag body 202 by the pump 204 from the tank 206 in which the scintillator is stored, the liquid scintillator injected into the bag body 202 is taken out, and the amount of the liquid scintillator stored in the bag body 202 The thickness of the bag body 202 may be changed by changing. Thereby, the sensitivity and image characteristics of the radiographic image to be taken can be changed. It should be noted that the bag body 202 is disposed on the TFT substrate 30 instead of the scintillator 8 so that the liquid scintillator is injected into the bag body 202 by the pump 204 and the liquid scintillator injected into the bag body 202 is taken out. Good. By filling or removing the liquid scintillator with the pump 204, the TFT substrate 30 can be brought into close contact with or separated from the TFT substrate 30. For example, when the TFT substrate 30 is deteriorated by radiation, only the TFT substrate 30 can be replaced.

Claims (9)

  A light emitting layer that generates light when irradiated with radiation, and a substrate provided with a plurality of sensor units each including an organic photoelectric conversion material that generates charges by receiving light are sequentially stacked, A radiation imaging apparatus comprising a radiation detector arranged so that radiation transmitted through a subject is incident from the substrate side. The radiation imaging apparatus according to claim 1, wherein the substrate is made of any one of plastic resin, aramid, bionanofiber, and a flexible glass substrate. The thin film transistor for reading the electric charge generated in each sensor part was formed in which the substrate comprises an amorphous oxide in an active layer corresponding to the sensor part. Radiography equipment. The radiation imaging apparatus according to any one of claims 1 to 3, wherein the substrate is attached to an imaging region irradiated with radiation that has passed through a subject in a housing. The light emitting layer includes a columnar crystal of CsI,
The radiographic apparatus according to any one of claims 1 to 4, wherein the organic photoelectric conversion material is quinacridone. A bag body that is arranged so as to overlap a detection region provided with a plurality of the sensor portions of the radiation detector, and whose opposing surface facing the detection region has at least light permeability;
A tank storing a liquid scintillator that emits light when irradiated with radiation;
The actuator which performs injection | pouring to the said bag body of the liquid scintillator stored in the said tank, and taking out of the liquid scintillator injected | thrown-in to the said bag body, It further provided with any one of Claims 1-5. Radiography equipment. The radiation imaging apparatus according to claim 1, wherein the two radiation detectors having different emission characteristics with respect to radiation of the light emitting layer are arranged to overlap each other. The light-emitting layers of the two radiation detectors are the thickness of each light-emitting layer, the particle size of each light-emitting layer, and the particle size of particles that emit light when irradiated with radiation, the layered structure of the particles, the filling rate of the particles, At least one change in the doping amount of the activator, the material of each light emitting layer, and the layer structure of each light emitting layer, and formation of a reflective layer that reflects the light on the surface of each light emitting layer that is not opposed to the substrate The radiation imaging apparatus according to claim 7, wherein either one is performed. The substrate is further formed with a thin film transistor for reading out electric charges generated in the sensor unit,
The sensor unit is configured using a wide gap semiconductor substrate,
The radiation imaging apparatus according to claim 1, wherein the radiation detector is stacked in the order of the light emitting layer, the sensor unit, and the thin film transistor, and is arranged so that the radiation is irradiated from the thin film transistor side.