Patent Publication Number: US-2019196032-A1

Title: Radiation detection device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Japanese Patent Application JP 2017-246645, filed Dec. 22, 2017, the entire content of which is hereby incorporated by reference, the same as if set forth at length. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a radiation detection device. 
     2. Description of the Related Art 
     A so-called flat panel detector (FPD) is used to acquire a radiographic image of an object. The FPD comprises, for example, a scintillator that emits fluorescence corresponding to the amount of incident radiation and a detection substrate on which pixels detecting the fluorescence emitted from the scintillator are two-dimensionally arranged. Radiation transmitted through the object is incident on the scintillator and each pixel converts the fluorescence generated from the scintillator into an electric signal. Radiographic image data of the object is generated on the basis of the electric signal output from each pixel. A so-called electronic cassette in which an FPD is accommodated in a housing and which is portable has been known as a radiation detection device comprising the FPD. 
     A radiation detection device disclosed in JP2000-258541A comprises a detection surface cover portion forming a detection surface on which radiation is incident and a housing that accommodates a radiation detection unit, which is an FPD, and is bonded to the detection surface cover portion. The housing has a frame that surrounds the outer periphery of the radiation detection unit and a bottom that is formed integrally with the frame. The detection surface cover portion overlaps an opening portion of the frame and a sealing member is interposed between the detection surface cover portion and the frame. 
     In a cassette for radiography disclosed in JP2013-076783A, a housing that accommodates an FPD includes: a front member including a rectangular top plate portion and a frame portion that is vertically provided at the edges of four sides of the top plate portion; and a back member that closes an opening provided in the bottom of the front member. The top plate portion and the frame portion are integrally formed. A connection portion between the top plate portion and the frame portion is chamfered. 
     In an electronic cassette disclosed in JP2016-65728A, a housing accommodating an image detection unit which is an FPD has a substantially rectangular parallelepiped shape having a front surface, a rear surface, and four side surfaces. The front surface and the four side surfaces are integrally formed. The front surface and the four side surfaces are connected to a smooth curved surface. 
     SUMMARY OF THE INVENTION 
     For example, an electronic cassette is inserted between the bed and an object that lies on his or her side on the bed and is then used. The load of the object is applied to the electronic cassette. In the radiation detection device disclosed in JP2000-258541A, the detection surface cover portion that comes into contact with the object is separated from the frame surrounding the outer periphery of the radiation detection unit. For example, in a case in which the radiation detection device is inserted between the object and the bed, there is a concern that the edge of the detection surface cover portion will be caught by the object and the rigidity of the detection surface cover portion against a load will be insufficient. Therefore, the radiation detection device needs to be handled with care. 
     In the cassette for radiography disclosed in JP2013-076783A, the top plate portion and the frame portion of the front member are integrally formed. Therefore, catching in a case in which the cassette is inserted between the object and the bed is prevented and the rigidity of the top plate portion and the frame portion is complementarily improved. However, the sealing between the front member and the back member that are separated from each other is not considered. In the electronic cassette disclosed in JP2016-65728A, the front surface and the four side surfaces are integrally formed. The sealing between the rear surface and the four side surfaces that are separated from each other is not considered. In a case in which a sealing performance is reduced, water is likely to be infiltrated into the housing and light is likely to be transmitted into the housing. There is a concern that, for example, the damage of the FPD and a radiation detection error will occur. 
     The invention has been made in view of the above-mentioned problems and an object of the invention is to provide a radiation detection device that is easy to handle and has a high sealing performance. 
     According to an aspect of the invention, there is provided a radiation detection device comprising: a radiation detection panel; and a housing that accommodates the radiation detection panel. The housing includes: a front member in which a top plate covering a radiation incident surface of the radiation detection panel and an outer frame surrounding an outer periphery of the radiation detection panel are integrally formed; a back member that closes an opening portion opposite to the top plate of the front member; and a first sealing member that has a ring shape and is interposed between the front member and the back member. The back member includes an inner frame that is fitted inside the outer frame. The first sealing member is interposed between the top plate and the inner frame in a direction in which the inner frame is fitted to the outer frame. 
     According to the invention, it is possible to provide a radiation detection device that is easy to handle and has a high sealing performance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating an example of a radiation detection device for describing an embodiment of the invention. 
         FIG. 2  is a cross-sectional view taken along the line II-II of  FIG. 1 . 
         FIG. 3  is a plan view illustrating the radiation detection device illustrated in  FIG. 1 . 
         FIG. 4  is a cross-sectional view taken along the line Iv-Iv of  FIG. 3 . 
         FIG. 5  is a cross-sectional view illustrating a modification example of the radiation detection device illustrated in  FIG. 1 . 
         FIG. 6  is a diagram schematically illustrating an example of a reinforcing portion provided in a back member of the radiation detection device illustrated in  FIG. 1 . 
         FIG. 7  is a diagram schematically illustrating an example of the arrangement of engagement portions provided in the back member of the radiation detection device illustrated in  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1 and 2  illustrate an example of a radiation detection device for describing an embodiment of the invention. 
     A radiation detection device  1  illustrated in  FIGS. 1 and 2  is a so-called electronic cassette and comprises a radiation detection panel  2  that detects radiation, such as X-rays, a supporting member  3  that supports the radiation detection panel  2 , and a housing  4  that accommodates the radiation detection panel  2  and the supporting member  3 . 
     The housing  4  is formed in a rectangular parallelepiped shape and typically has a size based on the International Organization for Standardization (ISO)  4090 : 2001 . The housing  4  includes a front member  5  and a back member  6 . 
     In the front member  5 , a top plate  7  that covers a radiation incident surface  2   a  of the radiation detection panel  2  and an outer frame  8  that surrounds the outer periphery of the radiation detection panel  2  are integrally formed. It is preferable that the front member  5  is made of a material which can reduce weight and increase load resistance. Examples of the material include a magnesium alloy, an aluminum alloy, a fiber reinforced resin, a cellulose nanofiber (CNF) reinforced resin, and a resin that satisfy a specific gravity of 3.0 or less and a Young&#39;s modulus of 1.8 GPa or more. The front member  5  is preferably made of a resin material, such as a fiber reinforced resin with high radiation transmittance, in consideration of the formation of the top plate  7  transmitting radiation. 
     In the back member  6 , an inner frame  10  that is fitted inside the outer frame  8  and a bottom  11  that is provided in an opening portion  9  opposite to the top plate  7  of the front member  5  are integrally formed. The back member  6  closes the opening portion  9 . It is preferable that the back member  6  is made of a material which can reduce weight and increase load resistance. Examples of the material include a magnesium alloy, an aluminum alloy, a fiber reinforced resin, a cellulose nanofiber (CNF) reinforced resin, and a resin that satisfy a specific gravity of 3.0 or less and a Young&#39;s modulus of 1.8 GPa or more. 
     The radiation detection panel  2  includes a scintillator  12  and a detection substrate  13  and is provided behind the top plate  7  in the housing  4 . The scintillator  12  has a phosphor, such as CsI:Tl (thallium-activated cesium iodide) or GOS (Gd 2 O 2 S:Tb, terbium-activated gadolinium oxysulfide) and emits fluorescence corresponding to the amount of incident radiation. The detection substrate  13  includes a plurality of pixels that are two-dimensionally arranged, detects fluorescence generated by the scintillator  12  with the pixels, and converts the detected fluorescence into an electric signal. 
     In the example illustrated in  FIGS. 1 and 2 , the scintillator  12  and the detection substrate  13  are stacked in the order of the scintillator  12  and the detection substrate  13  from the top plate  7  of the housing  4 . However, the scintillator  12  and the detection substrate  13  may be stacked in the order of the detection substrate  13  and the scintillator  12  from the top plate  7 . In addition, a direct-conversion-type radiation detection panel may be used in which a photoconductive film of each pixel of the detection substrate  13  that generates signal charge is made of, for example, amorphous selenium and which directly converts radiation into signal charge. 
     The supporting member  3  is a plate-shaped member and is formed in a rectangular shape. In the specification, the rectangular shape is not limited to a quadrangle with right-angled corners and includes a quadrangle with chamfered corners or a quadrangle with rounded corners. The supporting member  3  has a first surface  14  that faces the top plate  7  of the housing  4  and a second surface  15  that is opposite to the first surface  14 . The radiation detection panel  2  is supported by the first surface  14  of the supporting member  3 . It is preferable that the supporting member  3  is made of a material which can reduce weight and increase load resistance. Examples of the material include a magnesium alloy, an aluminum alloy, a fiber reinforced resin, a cellulose nanofiber (CNF) reinforced resin, and a resin that satisfy a specific gravity of 3.0 or less and a Young&#39;s modulus of 1.8 GPa or more. 
     The supporting member  3  is supported by a plurality of spacers  16  provided on the second surface  15  of the supporting member  3 . The spacers  16  are provided between the second surface  15  and the bottom  11  of the back member  6  which faces the second surface  15 . An appropriate space is formed between the supporting member  3  and the bottom  11 . The supporting member  3  is fixed to the back member  6  through the spacers  16 . 
     The spacers  16  may be formed integrally with the supporting member  3 . In a case in which the supporting member  3  is made of a metal material, such as an aluminum alloy or a magnesium alloy, the spacers  16  can be formed integrally with the supporting member  3  by, for example, casting or forging. In a case in which the supporting member  3  is made of a resin material, such as a fiber reinforced resin, the spacers  16  can be formed integrally with the supporting member  3  by, for example, vacuum molding. In addition, the spacers  16  may be formed separately from the supporting member  3  and may be bonded to the supporting member  3 . In this case, the material forming the spacers  16  is not particularly limited. The spacers  16  may be brought into contact with the bottom  11  of the housing  4  through a buffer material such as elastomer. 
     A circuit substrate  17  is provided between the supporting member  3  and the bottom  11 . For example, a driving control circuit that controls the driving of the detection substrate  13 , a signal processing circuit that processes the electric signal output from the detection substrate  13 , a communication circuit for communication with the outside, and a power circuit are formed on the circuit substrate  17 . The circuit substrate  17  is schematically illustrated as a single element in  FIG. 2 . However, the circuit substrate  17  may be divided into a plurality of circuit substrates and the plurality of circuit substrates may be dispersed between the supporting member  3  and the bottom  11 . 
     In addition, a power supply unit that supplies power to the detection substrate  13  and the circuit substrate  17  is provided between the supporting member  3  and the bottom  11 , which is not illustrated in the drawings. The power supply unit is a rechargeable battery, such as a lithium-ion secondary battery, or a capacitor, such as an electric double layer capacitor or a lithium-ion capacitor. 
     The detection substrate  13  of the radiation detection panel  2  which is provided on the first surface  14  of the supporting member  3  and the circuit substrate  17  which is provided on the second surface  15  of the supporting member  3  are connected to each other by a plurality of flexible substrates  18 . The flexible substrate  18  protrudes from the outer periphery of the radiation detection panel  2  to the outer frame  8  and the inner frame  10 , is bent in an arch shape so as to pass between the supporting member  3  and the outer frame  8  and the inner frame  10  of the housing  4 , and is connected to the circuit substrate  17 . 
     The housing  4  further includes a first sealing member  19  that has a ring shape and is interposed between the front member  5  and the back member  6 . The first sealing member  19  is an elastic body, such as silicone rubber or a foamed body, and is interposed between the top plate  7  and the inner frame  10  of the housing  4  in a direction in which the inner frame  10  is fitted to the outer frame  8  of the housing  4 . The front member  5  and the back member  6  are fixed to each other. In a state in which the front member  5  and the back member  6  are fixed to each other, the first sealing member  19  comes into close contact with the top plate  7  and the inner frame  10  to prevent the infiltration of water into the housing  4  and the transmission of light into the housing  4 . 
     Since the top plate  7  of the front member  5  and the outer frame  8  are integrally formed, the radiation detection device  1  is prevented from being caught in a case in which it is inserted between the object and the bed and it is easy to handle the radiation detection device  1 . In addition, since the top plate  7  and the outer frame  8  are integrally formed, the rigidity of the front member  5  is improved. Similarly, since the inner frame  10  and the bottom  11  are integrally formed, the rigidity of the back member  6  is improved. 
     The warpage of the top plate  7  is prevented according to the improvement in the rigidity of the front member  5  and the falling of the inner frame  10  is prevented according to the improvement in the rigidity of the back member  6 . Since the first sealing member  19  is interposed between the top plate  7  and the inner frame  10 , the close contact of the first sealing member  19  with the top plate  7  and the inner frame  10  is maintained even in a case in which a load is applied to the radiation detection device  1 . Therefore, it is possible to improve the sealing performance of the housing  4 . 
     For example, the radiation detection device  1  is assembled as follows. First, the radiation detection panel  2  is bonded to the first surface  14  of the supporting member  3  and the circuit substrate  17  and the power supply unit are bonded to the second surface  15  of the supporting member  3 . In this state, the supporting member  3  is fixed to the back member  6  through the plurality of spacers  16 . Then, the first sealing member  19  is placed on the inner frame  10  of the back member  6  and the back member  6  is covered with the front member  5 . As such, after the components accommodated in the housing, such as the radiation detection panel  2 , the supporting member  3 , the circuit substrate  17 , and the power supply unit, are mounted and fixed to the back member  6 , the front member  5  is attached. In this way, it is possible to improve assembly workability. 
       FIGS. 3 and 4  illustrate an example of the arrangement of fastening members for fixing the front member  5  and the back member  6 . 
     The housing  4  further includes a plurality of screws  20  as the fastening members for fixing the front member  5  and the back member  6 . The screws  20  are provided at appropriate intervals along four sides of the top plate  7  of the front member  5  and couple the top plate  7  to the inner frame  10  in the direction in which the inner frame  10  of the back member  6  is fitted to the outer frame  8  of the front member  5 . 
     The screws  20  pass through the top plate  7  and are engaged with the inner frame  10  of the back member  6 . Through holes  21  are formed in the top plate  7  and concave portions  23  that accommodate head portions  22  of the screws  20  passing through the through holes  21  are formed in the outer surface of the top plate  7 . Engagement portions  24  that are engaged with the screws  20  are provided in the inner frame  10  and screw holes are formed in the engagement portions  24 . The engagement portions  24  protrude from the inner surface of the inner frame  10  to the radiation detection panel  2  and the supporting member  3  and are formed integrally with the inner frame  10 . The screw  20  may pass through the inner frame  10  of the back member  6  and may be engaged with the top plate  7  of the front member  5 . In this case, the through holes are formed in the engagement portions  24  of the inner frame  10  and the screw holes are formed in the top plate  7 . 
     The outer frame  8  and the inner frame  10  may be coupled to each other in a direction intersecting the direction in which the inner frame  10  is fitted to the outer frame  8 . Since the top plate  7  and the inner frame  10  are coupled to each other in the direction in which the inner frame  10  is fitted to the outer frame  8 , it is possible to reliably compress the first sealing member  19  interposed between the top plate  7  and the inner frame  10  in the fitting direction and thus to improve the sealing performance of the housing  4 . 
     The screws  20  are arranged inside the first sealing member  19  with a ring shape. The screws  20  may be arranged outside the first sealing member  19 . Since the screws  20  are arranged inside the first sealing member  19 , it is possible to increase the width W of the first sealing member  19  and to improve the sealing performance of the housing  4 . The screws  20  and the engagement portions  24  are arranged at appropriate intervals. In a case in which the screws  20  are arranged outside the first sealing member  19 , the first sealing member  19  is retreated to the inside of the housing  4  over the entire periphery by a distance corresponding to the amount of protrusion P of the engagement portion  24 . The inner surface of the inner frame  10  that faces the top plate  7  with the first sealing member  19  interposed therebetween is also retreated to the inside of the housing  4  over the entire periphery. Therefore, the clearance between the inner frame  10 , and the radiation detection panel  2  and the supporting member  3  is reduced over the entire periphery. The width W of the first sealing member  19  is reduced in order to ensure the clearance. In contrast, in a case in which the screws  20  are arranged inside the first sealing member  19 , the clearance is reduced by the engagement portion  24  protruding from the inner surface of the inner frame  10  at the position where the screws are arranged. However, the clearance is relatively large between two adjacent screw arrangement positions, that is, between two adjacent engagement portions  24 . Therefore, it is possible to ensure the clearance and to increase the width W of the first sealing member  19  by arranging the screws  20  except a housing part in which a relatively large deformation is expected to occur in a case in which the radiation detection device  1  falls on, for example, a floor. 
     Preferably, the screws  20  are provided along four sides of the top plate  7  except four corners of the top plate  7 , as illustrated in  FIG. 3 . A relatively large deformation is expected to occur at the corners of the housing  4  in a case in which the radiation detection device  1  falls on, for example, a floor. However, since the screws  20  are provided except four corners of the top plate  7 , the clearance between the inner frame  10 , and the radiation detection panel  2  and the supporting member  3  is ensured at the corners. Therefore, it is possible to prevent the collision of the inner frame  10  with the radiation detection panel  2  and the supporting member  3  caused by the deformation of the corners and to prevent the damage of the radiation detection panel  2 . 
     Since the screws  20  are arranged inside the first sealing member  19 , the through holes  21  of the top plate  7  directly communicate with the inside of the housing  4 . The housing  4  includes second sealing members that seal the through holes  21 . In the example illustrated in  FIG. 4 , the second sealing member is an O-ring  25  that is attached to the screw  20 . The O-ring  25  is interposed between the head portion  22  of the screw  20  and the concave portion  23  in the outer surface of the top plate  7 . The second sealing member is not limited to the O-ring. As illustrated in  FIG. 5 , the second sealing member may be a sheet  26  that is attached to the outer surface of the top plate  7  to close the concave portions  23 . Even in a case in which the through hole is formed in the engagement portion  24  of the inner frame  10  instead of the top plate  7 , the second sealing member, such as the O-ring  25  and the sheet  26 , can be applied. 
     Preferably, reinforcing portions  27  are provided at four corners of the bottom  11  of the back member  6 , as illustrated in  FIG. 4 . The screws  20  are not provided at four corners of the top plate  7  and the compression of the first sealing member  19  based on the coupling between the top plate  7  and the inner frame  10  through the screws  20  is relatively weak at the four corners of the top plate  7 . Since the reinforcing portions  27  are provided at four corners of the bottom  11 , it is possible to prevent the warpage of the four corners of the bottom  11  caused by the reaction force of the first sealing member  19  and to compensate for the compression of the first sealing member  19 . 
     The reinforcing portions  27  provided at four corners of the bottom  11  may be, for example, ribs that protrude from the bottom  11  to the top plate  7  as illustrated in  FIG. 6 . In the example illustrated in  FIG. 6 , the reinforcing portion  27  includes two ribs, that is, a quadrangular rib  28  having one corner A that faces the center of the bottom  11  and a rib  29  that connects the corner A and an opposing corner B. The reinforcing portion  27  is not limited to the example illustrated in  FIG. 6  as long as it can prevent the warpage of the four corners of the bottom  11 . 
     Preferably, a region L out  outside a frame line L (see  FIG. 3 ) that is formed by connecting the screws  20  along four corners of the top plate  7  is thicker than a region L in  inside the frame line L in the top plate  7 , as illustrated in  FIG. 4 . This configuration makes it possible to increase the rigidity of the front member  5 , without reducing radiation transmittance. Even in a case in which a load is applied to the radiation detection device  1 , it is possible to maintain the close contact of the top plate  7  and the inner frame  10  with the first sealing member  19  and to improve the sealing performance of the housing  4 . 
       FIG. 7  illustrates an example of the arrangement of the engagement portions  24 , which are engaged with the screws  20 , on the inner frame  10 . 
     In the example illustrated in  FIG. 7 , the flexible substrates  18  connecting the radiation detection panel  2  and the circuit substrate  17  are arranged at intervals along the edge (one side) of at least a portion of the outer periphery of the radiation detection panel  2 . The engagement portions  24  are provided on one surface  10   a  of the inner frame  10  which faces one side of the radiation detection panel  2  along which the flexible substrates  18  are arranged. The engagement portions  24  protrude from the one surface  10   a  of the inner frame  10  to the radiation detection panel  2  and the supporting member  3 . The engagement portion  24  is provided between two adjacent flexible substrates  18 . 
     Since the engagement portion  24  is provided between two adjacent flexible substrates  18 , it is possible to ensure the clearance between the engagement portion  24 , and the radiation detection panel  2  and the supporting member  3  and the clearance between the flexible substrate  18  and the inner frame  10 , to widen the radiation detection panel  2  and the supporting member  3 , and expand an effective pixel region of the radiation detection panel  2  (detection substrate  13 ). 
     As described above, a radiation detection device disclosed in the specification comprises a radiation detection panel and a housing that accommodates the radiation detection panel. The housing includes: a front member in which a top plate covering a radiation incident surface of the radiation detection panel and an outer frame surrounding an outer periphery of the radiation detection panel are integrally formed; a back member that closes an opening portion opposite to the top plate of the front member; and a first sealing member that has a ring shape and is interposed between the front member and the back member. The back member includes an inner frame that is fitted inside the outer frame. The first sealing member is interposed between the top plate and the inner frame in a direction in which the inner frame is fitted to the outer frame. 
     In the radiation detection device disclosed in the specification, the housing includes a plurality of fastening members that couple the top plate to the inner frame in the fitting direction. 
     In the radiation detection device disclosed in the specification, the fastening members are provided inside the first sealing member. 
     In the radiation detection device disclosed in the specification, the fastening member passes through one of the top plate and the inner frame and is engaged with the other. The housing includes a second sealing member that seals a through hole formed in the top plate or the inner frame. 
     The radiation detection device disclosed in the specification further comprises: a circuit substrate that is provided on a rear surface side opposite to the radiation incident surface of the radiation detection panel and is accommodated in the housing; and a plurality of flexible substrates that connect the radiation detection panel and the circuit substrate. The flexible substrates are arranged at intervals along an edge of at least a portion of the outer periphery of the radiation detection panel and protrude from the outer periphery of the radiation detection panel to the outer frame and the inner frame while being bent in an arch shape. The inner frame includes engagement portions which are engaged with the fastening members and each of which is provided between two adjacent flexible substrates. 
     In the radiation detection device disclosed in the specification, the housing has a rectangular parallelepiped shape and the fastening members are provided along four sides of the top plate except four corners of the top plate. 
     In the radiation detection device disclosed in the specification, the back member has a bottom provided in the opening portion and reinforcing portions are provided at four corners of the bottom. 
     In the radiation detection device disclosed in the specification, the reinforcing portion is one or more ribs that protrude from the bottom to the top plate. 
     In the radiation detection device disclosed in the specification, a region outside a frame line that is formed by connecting the fastening members along the four sides of the top plate is thicker than a region inside the frame line in the top plate. 
     EXPLANATION OF REFERENCES 
     
         
         
           
               1 : radiation detection device 
               2 : radiation detection panel 
               2   a : radiation incident surface of radiation detection panel 
               3 : supporting member 
               4 : housing 
               5 : front member 
               6 : back member 
               7 : top plate 
               8 : outer frame 
               9 : opening portion of outer frame 
               10 : inner frame 
               10   a : one surface of inner frame 
               11 : bottom 
               12 : scintillator 
               13 : detection substrate 
               14 : first surface of supporting member 
               15 : second surface of supporting member 
               16 : spacer 
               17 : circuit substrate 
               18 : flexible substrate 
               19 : first sealing member 
               20 : screw (fastening member) 
               21 : through hole 
               22 : head portion of screw 
               23 : concave portion 
               24 : engagement portion 
               25 : O-ring (second sealing member) 
               26 : sheet (second sealing member) 
               27 : reinforcing portion 
               28 : rib 
               29 : rib 
             A: corner 
             B: opposing corner 
             L: frame line 
             L out : region outside frame line 
             L in : region inside frame line 
             P: amount of protrusion of engagement portion 
             W: width of first sealing member