JP2012122841A - Electronic cassette - Google Patents

Abstract

An electronic cassette is reduced in size and thickness.
A scintillator for converting irradiated X-rays into light, and means for converting light emitted from the scintillators into electrical signals, which are disposed in front of the scintillator in the incident direction of the X-rays. , A TFT substrate 42 arranged with a detection element array 44 made of photodiodes and TFTs for performing photoelectric conversion facing the scintillator 41, and a circuit board for processing electrical signals output from the TFT substrate 42 36 to 39, and flexible connection means for connecting the TFT substrate 42 and the circuit substrates 36 to 39, and the TFT substrate 42 is hidden behind the TFT substrate 42 in a state where the TFT substrate 42 and the circuit substrates 36 to 39 are connected. 42 and a flexible substrate 46 for connecting the circuit boards 36 to 39.
[Selection] Figure 5

Description

  The present invention relates to an electronic cassette that acquires a radiation image using a radiation detection panel of a system (ISS (Irradiation Side Sampling) system) that detects radiation by arranging a light detection element on the radiation incident side with respect to the scintillator. It is.

  In the field of radiography, an X-ray sensitive layer (scintillator) is placed on a TFT (Thin Film Transistor) active matrix substrate (hereinafter referred to as TFT substrate) as a radiation detection panel, and incident X-rays are converted into digital data. Flat panel detectors (FPDs) have been put into practical use. In addition, a portable X-ray (radiation) image detection device that generates an X-ray image represented by X-rays transmitted through a subject using an FPD and stores the generated X-ray image ( Hereinafter, “electronic cassette” has been put into practical use.

  As an FPD, a PSS (Penetration Side Sampling) type FPD in which a scintillator and a TFT substrate are arranged in this order from the X-ray incident side is known. Usually, the TFT substrate is arranged with the light detection surface facing the scintillator. Therefore, in the PSS type FPD, the light detection surface of the TFT substrate is arranged toward the X-ray incident side. In addition, a control substrate for controlling the TFT substrate is disposed on the back surface of the TFT substrate. In this way, the light detection surface is disposed toward the X-ray incident side, and the control substrate and the like are disposed on the back surface of the TFT substrate. Therefore, the flexible substrate that connects them extends to the outside of the TFT substrate. Are bent so as to wrap around the outer edge of the TFT substrate, and are connected to the control substrate on the back surface (Patent Document 1).

  In addition, the ISS system is known as a system that is advantageous for higher resolution than the PSS system. The ISS system is a system in which the TFT substrate and the scintillator are arranged in this order from the X-ray incident side. Also in the ISS system, the light detection surface of the TFT substrate is arranged facing the scintillator as in the PSS system. In the ISS system, the TFT substrate is disposed so that the light detection surface faces the back side. However, the conventional ISS type FPD follows the connection structure by the flexible substrate in the PSS method, and is attached by extending the flexible substrate to the outside of the TFT substrate, and is curved so as to protrude from the TFT substrate, and is the control substrate on the back surface. Etc. (Patent Document 2).

JP 2010-197404 A JP 2010-237138 A

  Electronic cassettes are required to be small and thin in order to facilitate handling and improve portability. However, the conventional ISS type FPD is attached so that the flexible substrate extends to the outside of the TFT substrate, and the flexible substrate protrudes from the TFT substrate, so the arrangement space of the flexible substrate hinders the reduction in size and thickness. ing.

  The present invention has been made in view of the above-described problems, and it is an object of the present invention to reduce the wiring space of a flexible substrate and reduce the size and thickness of an electronic cassette.

  The electronic cassette according to the present invention has a scintillator that converts irradiated radiation into light, and a light detection surface that is disposed in front of the scintillator in the radiation irradiation direction and that has a photoelectric conversion element faces the scintillator. A photoelectric conversion means for converting light emitted from the scintillator into an electric signal by the photoelectric conversion element; a signal processing means for processing the electric signal output from the photoelectric conversion substrate; and the photoelectric conversion. Connecting means for connecting the photoelectric conversion means and the signal processing means so as to be hidden behind the photoelectric conversion means in a state where the photoelectric conversion means and the signal processing means are connected. And an electronic cassette.

  One end of the connection means is preferably connected to the light detection surface and attached to the inside of the light detection surface in a direction in which the other end extends.

  The connecting means is preferably a flexible printed circuit board.

  It is preferable that a circuit element responsible for processing the electrical signal output from the photoelectric conversion unit is provided together with the signal processing unit on the flexible printed board.

  The circuit element provided on the flexible printed circuit board is attached to a position exposed on the outer surface of the flexible printed circuit board when the photoelectric conversion means and the signal processing means are connected by the flexible printed circuit board. It is preferable.

  The scintillator is composed of a phosphor that converts to a fluorescence having a light emission amount corresponding to an incident dose of the radiation, and a support that supports the phosphor, and the scintillator is disposed in contact with the phosphor and the light detection surface. It is preferable.

  The support is preferably made of a material having the same coefficient of thermal expansion as the photoelectric conversion means.

  The support is preferably made of a glass substrate or a carbon plate.

  The support is preferably fixed to a housing.

  The support is preferably made of a conductive material.

  According to the present invention, the wiring space of the flexible substrate can be reduced, and the electronic cassette can be reduced in size and thickness.

It is the schematic which shows the structure of a X-ray imaging system. It is a disassembled perspective view of an electronic cassette. It is sectional drawing of an electronic cassette. It is a perspective view which shows the structure of the back side of an X-ray detection panel. It is explanatory drawing which shows the effect | action of this invention. It is explanatory drawing which shows the effect | action of this invention. It is explanatory drawing which shows the attachment aspect of a flexible substrate suitable when extending a flexible substrate toward the outer side of a TFT substrate. It is sectional drawing which shows the structural example of a scintillator. It is a figure which shows the example of attachment of the support body to a front panel.

  As shown in FIG. 1, the X-ray imaging system 10 includes an X-ray generator 11, a supine imaging table 12, an electronic cassette 13, a console 14, and a monitor 15. Based on the control of the console 14, the electronic cassette 13 detects the X-rays that are transmitted through the subject H from the X-ray generator 11, and generates an X-ray image. The console 14 performs various types of image processing on the X-ray image transmitted from the electronic cassette 13 and displays the image on the monitor 15. The tray 21 is an attachment portion to which the electronic cassette 13 is detachably attached.

  In the X-ray imaging system 10, the X-ray generator 11 emits X-rays from above toward the subject H placed on the supine imaging table 12, and the X-rays pass through the subject H. The X-ray image obtained in this way is detected by the electronic cassette 13. Further, in photographing the limbs and the elbows, the electronic cassette 13 may be placed on the lying position photographing stand 12 for photographing.

  The electronic cassette 13 has a substantially rectangular parallelepiped shape. For example, the electronic cassette 13 has an outer size conforming to the international standard ISO 4090: 2001 similar to a cassette for a half-cut size (383.5 mm × 459.5 mm) or IP. ing. The external size of the electronic cassette 13 includes a four-cut size, a six-cut size, etc. in addition to the half-cut size described above, and is appropriately selected according to the imaging region.

  As shown in FIGS. 2 and 3, the electronic cassette 13 includes a housing 31, an X-ray detection panel 32 housed in the housing 31, a base plate 34, circuit boards 36 to 39, and the like.

  The housing 31 is formed in a hollow rectangular parallelepiped shape including a front surface portion 31a and a back surface portion 31b, and accommodates each portion of the electronic cassette 13 such as the X-ray detection panel 32 therein. The casing 31 is made of a metal having a low X-ray transmittance, such as stainless steel. The front surface portion 31a covers the X-ray detection panel 32 from the front surface side where X-rays are incident, and is provided with an X-ray transmission window 33 formed of a carbon plate.

  The X-ray detection panel 32 includes a scintillator 41 that converts incident X-rays into fluorescence, and a TFT substrate 42 that accumulates signal charges corresponding to the incident dose of X-rays by photoelectrically converting light generated by the scintillator 41. Consists of.

  The scintillator 41 is an element that converts X-rays into fluorescence, and includes, for example, a phosphor such as cesium iodide (CsI) or gadolinium oxysulfide (GOS). When the X-rays are incident, the scintillator 41 absorbs the X-rays, and emits fluorescence having a light emission amount corresponding to the incident dose by the phosphor. The scintillator 41 is manufactured by a method such as vapor deposition (or application) of a phosphor on a support body 41a made of aluminum or the like, or direct vapor deposition on the surface of the TFT substrate 42. In this example, the scintillator 41 is different from the TFT substrate 42. An example of manufacturing on a separate support body 41a will be described.

  The TFT substrate 42 is a substrate on which a detection element array 44 is formed on a glass substrate 43, and detects light generated by the scintillator 41 and converts it into electric charges when X-rays enter. The detection element array 44 is formed by arranging detection elements including photodiodes (light detection elements) and TFTs in a matrix. Since the TFT substrate 42 detects light by the detection element array 44, the surface on which the detection element array 44 is provided is a light detection surface.

  The photodiode has a photoconductive layer that is sensitive to fluorescence, and generates a signal charge corresponding to the amount of incident light by photoelectrically converting light incident from the scintillator 41. The photoconductive layer forming the photodiode is made of, for example, amorphous silicon (a-Si). The TFT is a switching element that switches between accumulation and readout of signal charges, and is provided in each photodiode.

  The electronic cassette 13 is an ISS FPD. For this reason, the X-ray detection panel 32 is arranged so that the TFT substrate 42 and the scintillator 41 are arranged in this order from the front surface portion 31a side where the X-rays are incident. At this time, the light detection surface of the TFT substrate 42 provided with the detection element array 44 is disposed toward the scintillator 41 side. The scintillator 41 is arranged with the phosphor facing the light detection surface of the TFT substrate 42. The TFT substrate 42 and the scintillator 41 are fixed with an adhesive so that the light detection surface and the phosphor are in contact with each other, and the front surface (surface on the front surface portion 31a side) of the TFT substrate 42 is on the inner surface of the front surface portion 31a. It is fixed with an adhesive. Therefore, the X-ray detection panel 32 is fixed to the housing 31 by the front surface portion 31a. Further, since the amount of light emitted from the scintillator 41 is the largest on the front surface, which is the incident surface on which X-rays enter, the front surface of the scintillator 41 and the light detection surface of the TFT substrate 42 are opposed to each other, so Efficiency is obtained.

  The base plate 34 is a member for fixing the circuit boards 36 to 39 to the housing 31 and is made of, for example, stainless steel. The base plate 34 is used by being fixed to the housing 31 by screws or the like with the X-ray detection panel 32 and the circuit boards 36 to 39 attached thereto. A cutout 34 a is provided at the end of the base plate 34.

  The circuit boards 36 to 39 are arranged on the back surface portion 31b side of the base plate 34, and the X-ray detection panel 32 (TFT substrate 42) and the circuit boards 36 to 39 arranged on the front surface portion 31a side of the base plate 34 are They are connected by a flexible substrate 46 inserted through the notch 34a.

  The circuit board 36 is a drive circuit board on which a drive circuit for driving the TFTs of the detection element array 44 is formed. The circuit board 37 is an A / D conversion circuit board on which an A / D conversion circuit is formed. The A / D conversion circuit converts an analog signal output from an IC chip described later into a digital signal.

  The circuit board 38 is a control board on which a control circuit is formed. The control circuit controls each part of the X-ray detection panel 32 and controls communication with the console 14. The circuit board 39 is a power circuit board on which a power circuit is formed. The power supply circuit includes circuit elements such as an AC / DC converter that converts alternating current into direct current, and a DC / DC converter that converts direct current voltage into a voltage necessary for the operation of each circuit, and supplies power to each section.

  The driving circuit board 36 and the A / D conversion circuit board 37 are connected to the X-ray detection panel 32 (TFT substrate 42) by a flexible board 46, respectively. TCP (tape carrier package) type IC chips 53 and 54 are mounted on the flexible substrate 46.

  The IC chip 53 is a shift register that constitutes a drive circuit together with circuit elements formed on the circuit board 36. The IC chip 54 includes a charge amplifier that converts a signal charge read from the X-ray detection panel 32 into a voltage signal, and This is an ASIC that constitutes a readout circuit including a multiplexer for sequentially switching the columns of the detection element array 44 and outputting a voltage signal column by column. The readout circuit and the A / D conversion circuit are signal processing circuits that process signals output from the X-ray detection panel 32. The circuit elements 56 mounted on the circuit boards 36 to 39 and the IC chips 53 and 54 mounted on the flexible board 46 are electric components for causing the X-ray detection panel 32 to function.

  As shown in FIG. 4, the flexible substrate 46 is connected to the light detection surface 61 of the TFT substrate 42 by thermocompression bonding at one end. The flexible substrate 46 is attached to the TFT substrate 42 in such a direction that the other end provided with the connector 62 connected to each of the circuit substrates 36 to 39 extends inward of the TFT substrate 42.

  In order to prevent a connection failure such as disconnection due to bending of the flexible substrate 46 and to realize a stable connection between the TFT substrate 42 and each of the circuit substrates 36 to 39, the bending radius of the conductive wire portion of the flexible substrate 46 is within a certain range. Need to fit.

  As shown by a two-dot chain line in FIG. 5, when the flexible substrate 46 is attached in a direction extending to the outside of the TFT substrate 42, the bending angle of the conductive wire portion 63 of the flexible substrate 46 is 180 degrees, and the bending radius of the flexible substrate 46 is Since the metal layer of the flexible substrate 46 has to be larger than the minimum radius at which the metal layer is not broken and broken, the base plate 34 needs to be arranged away from the X-ray detection panel 32. Further, when the flexible substrate 46 is attached in a direction extending to the outside of the TFT substrate 42, the conductive wire portion 63 protrudes outside the TFT substrate 42. Therefore, the space for arranging the flexible substrate 46 between the TFT substrate 42 and the front surface portion 31a is increased. It is necessary to secure.

  On the other hand, as shown by a solid line in FIG. 5, in this embodiment, the flexible substrate 46 is attached in a direction extending to the inside of the TFT substrate 42, so that the flexible substrate 46 and the TFT substrate 42 are in a substantially flat state. The substrates 36 to 39 can be connected. For this reason, there is almost no need to consider the bending radius of the flexible substrate 46, and the base plate 34 and the X-ray detection panel 32 can be arranged close to each other as close as possible. Therefore, the electronic cassette 13 can be thinned by attaching the flexible substrate 46 so as to extend inside the TFT substrate 42.

  Further, when the flexible substrate 46 is attached in a direction extending to the inside of the TFT substrate 42, the flexible substrate 46 is entirely contained behind the TFT substrate 42 (in the surface on the light detection surface 61 side). For this reason, it is not necessary to secure a space for arranging the conductive wire portion 63 of the flexible substrate 46 between the TFT substrate 42 and the housing 31 (front surface portion 31a). Therefore, the electronic cassette 13 can be reduced in size by attaching the flexible substrate 46 in a direction extending to the inside of the TFT substrate 42. Further, since the X-ray dose irradiated to the flexible substrate 46 is reduced, malfunctions and failures of the IC chips 53 and 54 can be prevented.

  Further, comparing the case where the flexible substrate 46 is attached in a direction extending toward the inside of the TFT substrate 42 and the case where the flexible substrate 46 is attached toward the outside, the length of the flexible substrate 46 extends toward the inside of the TFT substrate 42. It is possible to make it shorter. For this reason, noise generated by connecting the X-ray detection panel 32 and the circuit boards 36 to 39 by the flexible board 46 can be reduced.

  Further, when the flexible substrate 46 is attached so as to extend inside the TFT substrate 42, the bending angle is small, thereby reducing the force in the peeling direction applied to one end of the flexible substrate 46 connected to the TFT substrate 42 by thermocompression bonding. Can do. Thereby, it is possible to prevent the flexible substrate 46 from being disconnected from the TFT substrate 42 when the electronic cassette 13 is assembled.

  In addition, as shown in FIG. 6, these are compared with the case where the flexible substrate 46 is attached in the direction extending to the outside of the TFT substrate 42 and the base plate 34 is brought into close contact with the X-ray detection panel 32. It is the same. That is, in order to keep the bending angle of the flexible substrate 46 below a certain angle, the space for arranging the conductive wire portion 63 of the flexible substrate 46 hinders the electronic cassette 13 from being thinned and miniaturized. In order to suppress the bending angle of the flexible substrate 46 when the flexible substrate 46 is attached in the direction extending to the outside of the TFT substrate 42 and the base plate 34 is brought into close contact with the X-ray detection panel 32, the flexible substrate 46 is used. Therefore, the influence of noise increases. For this reason, it is preferable to attach the flexible substrate 46 so as to extend toward the inside of the TFT substrate 42.

  In the above-described embodiment, the flexible substrate 46 is thermocompression bonded to the back surface (light detection surface 61) of the TFT substrate 42, and the other end of the flexible substrate 46 is connected to each circuit substrate 36 by the connector 62. The connection mode of the flexible substrate 46 is not limited to this example. For example, when the electronic cassette 13 is assembled, the other end of the flexible substrate 46 may be connected to each circuit board 36 by thermocompression bonding. Further, the connection to the TFT substrate 42 may be a connection by the connector 62.

  In the above-described embodiment, an example in which the flexible substrate 46 is attached so as to extend inside the TFT substrate 42 so that the entire flexible substrate 46 is hidden behind the TFT substrate 42 has been described. Not limited to. As shown in FIG. 7, the flexible substrate 46 is attached so that the entire flexible substrate 46 is hidden behind the TFT substrate 42 even when the flexible substrate 46 is attached to extend outside the TFT substrate 42 as in the conventional case. Is preferred. In order to attach the flexible substrate 46 in this way, for example, the attachment position of the flexible substrate 46 to the TFT substrate 42 may be more inside the TFT substrate 42. If the flexible substrate 46 is attached so as to be completely hidden behind the TFT substrate 42, it is not necessary to increase the size of the electronic cassette 13 in order to ensure the space for arranging the flexible substrate 46.

  In the above-described embodiment, the IC chips 53 and 54 are provided on the surface of the flexible substrate 46 so as to be as close as possible to the TFT substrate 42. However, since the flexible substrate 46 is shorter than the conventional one, the IC chips 53 and 54 are You may provide in the base board 34 similarly to each circuit board 36-39. Further, the IC chips 53 and 54 may be provided integrally with the circuit boards 36 to 39.

  Furthermore, in the above-described embodiment, the example in which the IC chips 53 and 54 are exposed to the outside of the flexible substrate 46 when the flexible substrate 46 and the circuit boards 36 to 39 are connected has been described. May be arranged inside the flexible substrate 46 so that the flexible substrate 46 and the circuit boards 36 to 39 are connected to each other so as to be hidden on the inner surface side of the flexible substrate 46. When the flexible substrate 46 and each circuit board 36 to 39 are connected, the surface of the flexible substrate 46 exposed on the opposite side of the TFT substrate 42 or the like is the outer surface, and the flexible substrate 46 and each circuit board 36 to 39 are connected. In this case, the surface of the flexible substrate 46 that is directed to the TFT substrate side is defined as the inner surface.

  In the above-described embodiment, the case 31 and the base plate 34 are formed of stainless steel. However, the casing 31 and the base plate 34 may be made of any material as long as the material shields X-rays. Can do. For example, a copper-based material or an aluminum plate obtained by vapor-depositing a copper foil can be suitably used as the casing 31 and the base plate 34. If a material having a thermal expansion coefficient equal to (or close to) that of the TFT substrate 42, such as a glass substrate or a carbon plate, is used as the support 71, it is easy to reduce the warp of the X-ray detection panel 32, and the TFT substrate 42 and the scintillator 41 (fluorescence). The peeling of the body 72) can be prevented.

  In the above-described embodiment, the example in which the scintillator 41 is bonded and fixed to the TFT substrate 42 has been described. However, the present invention is not limited to this. As shown in FIGS. 8 and 9, when the scintillator 41 is formed by vapor-depositing (or coating) the phosphor 72 on the aluminum support 71, the support 71 is formed larger than the phosphor 72. The support 71 is preferably fixed to the housing (for example, the front surface portion 31a) with screws 73 or the like. In this case, similarly to the base plate 34, a notch 74 through which the flexible substrate 46 is inserted is provided at the end of the support 71. The phosphor 72 and the TFT substrate 42 are fixed with an adhesive as in the above embodiment, but the TFT substrate 42 and the front surface portion 31a are not bonded.

  Thus, when the scintillator 41 is manufactured by vapor-depositing the phosphor 72 on the support 71, the rigidity of the X-ray detection panel 32 can be improved by fixing the support 71 of the scintillator 41 to the housing 31. The phosphor 72 has heat at the time of X-ray imaging, and can prevent warping of the scintillator 41 and the TFT substrate 42 and peeling of the scintillator 41 and the TFT substrate 42 due to this heat.

  Further, since the X-ray detection panel 32 is screwed without being bonded to the housing 31, the X-ray detection panel 32 can be easily removed. Thereby, maintenance and reuse of the X-ray detection panel 32 can be easily performed. When the support 71 is made of a conductive material such as a metal plate, the phosphor 72 is grounded to the casing 31 through the support 71, so that the phosphor 72 can be prevented from being charged.

  In the above-described embodiment, the example in which the circuit board 36 is provided on the back side (back side 31b side) of the base plate 34 has been described. However, the base plate 34 and the scintillator 41 are arranged apart from each other, and each circuit board is provided. 36 to 39 may be provided on the front surface portion 31 a side of the base plate 34.

  In the above-described embodiment, an example in which X-rays are used as an example of radiation has been described, but other radiation may be used.

DESCRIPTION OF SYMBOLS 10 X-ray imaging system 11 X-ray generator 12 Positional imaging stand 13 Electronic cassette 14 Console 15 Monitor 21 Tray 31 Case 31a Front part 31b Rear part 32 X-ray detection panel 33 X-ray transmissive window 34 Base board 34a Notch 36 To 39 circuit board 41 scintillator 42 TFT substrate 43 glass substrate 44 detection element array 46 flexible substrate 53, 54 IC chip 56 circuit element 61 photodetection surface 62 connector 63 conductor portion 71 support 72 phosphor 73 screw 74 notch

Claims (10)

A scintillator that converts the irradiated radiation into light;
The light detection surface disposed in front of the scintillator in the irradiation direction of the radiation and provided with a photoelectric conversion element is provided so as to face the scintillator, and the light emitted from the scintillator is transmitted by the photoelectric conversion element. Photoelectric conversion means for converting into an electrical signal;
Signal processing means for processing the electrical signal output by the photoelectric conversion substrate;
A connecting means for connecting the photoelectric conversion means and the signal processing means, the photoelectric conversion means and the signal processing being hidden behind the photoelectric conversion means in a state where the photoelectric conversion means and the signal processing means are connected; Connecting means for connecting the means;
An electronic cassette characterized by comprising:   The electronic cassette according to claim 1, wherein one end of the connection means is connected to the light detection surface and attached to the inside of the light detection surface in a direction in which the other end extends.   The electronic cassette according to claim 1, wherein the connecting means is a flexible printed circuit board.   4. The electronic cassette according to claim 3, wherein a circuit element responsible for processing the electrical signal output from the photoelectric conversion means is provided together with the signal processing means on the flexible printed board.   The circuit element provided on the flexible printed circuit board is attached to a position exposed on the outer surface of the flexible printed circuit board when the photoelectric conversion means and the signal processing means are connected by the flexible printed circuit board. The electronic cassette according to claim 4.   The scintillator is composed of a phosphor that converts to a fluorescence having a light emission amount corresponding to an incident dose of the radiation, and a support that supports the phosphor, and the scintillator is disposed in contact with the phosphor and the light detection surface. The electronic cassette according to any one of claims 1 to 5, wherein:   The electronic cassette according to claim 6, wherein the support is made of a material having a thermal expansion coefficient equal to that of the photoelectric conversion means.   The electronic cassette according to claim 7, wherein the support is made of a glass substrate or a carbon plate.   The electronic cassette according to claim 6, wherein the support is fixed to a housing.   The electronic cassette according to claim 7, wherein the support is made of a conductive material.

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