Patent Publication Number: US-10325460-B2

Title: Cassette

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of application Ser. No. 15/615897 filed on Jun. 7, 2017, which claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2016-126604, filed on Jun. 27, 2016. Each of the above application(s) is hereby expressly incorporated by reference, in its entirety, into the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a cassette. 
     2. Description of the Related Art 
     In the related art, radiation detection cassettes have been widely used in radiation imaging, such as X-ray imaging. The radiation detection cassettes are portable radiation detection devices including a rectangular housing, and a radiation detector that is housed within the housing and detects radiation transmitted through a subject. 
     The radiation detection cassettes are capable of being used by being attached to a stationary imaging stand where a subject is imaged in a standing posture or lying posture. In addition, the radiation detection cassettes are used by being put on a bed in order to image a site (for example, limbs) where imaging is difficult in the stationary imaging stand or by being carried by the subject himself or herself. Additionally, in order to image elderly people under recuperation at home or emergency cases due to an accident, disaster, or the like, the radiation detection cassettes may be used by being carried to the outside of hospitals without equipment of the imaging stand. 
     SUMMARY OF THE INVENTION 
     Here, the housing of the related-art radiation detection cassettes include a transmission plate that is arranged on a radiation exposure side and that allows radiation to be transmitted therethrough, and a back surface plate that is arranged to face the transmission plate. For example, an Mg alloy consisting of Mg (magnesium), Al (aluminum), and Zn (zinc) is used as the back surface plate. 
     Since the radiation detection cassettes are carried by a person, it is desirable that the radiation detection cassettes are light-weight, and it is desirable to use an alloy containing Mg and Li (lithium) whose specific gravity is smaller than that of the above Mg alloy (for example, refer to JP2011-084818A). 
     Meanwhile, recesses partitioned by ribs or the like are formed in an inner surface of the back surface plate. In a case where the recesses are formed by cutting work, it is necessary to perform grooving using an end mill or the like on a material in which no recesses are formed. 
     However, in a case where such grooving is performed, since an escape places for the heat of a blade of the end mill is small, the blade is heated, and the alloy containing Mg and Li whose melting point is lower than the above Mg alloy deposits on the blade of the end mill. As a result, the recess cannot be formed appropriately. 
     In view of the above problems, an object of the invention is to provide a cassette having a transmission plate disposed on radiation exposure side and transmitting radiation, and a housing part disposed on opposite to the radiation exposure side, the cassette comprises a radiation detector that is disposed between the transmission plate and the housing part, material of the housing part contains 5 mass % or more and 25 mass % or less of Li. 
     Means for Solving the Problems 
     According to an aspect of the invention, there is provided a cassette having a transmission plate disposed on radiation exposure side and transmitting radiation, and a housing part disposed on opposite to the radiation exposure side. The cassette comprises a radiation detector that is disposed between the transmission plate and the housing part, in which material of the housing part contains 5 mass % or more and 25 mass % or less of Li. 
     Additionally, the cassette of the above aspect of the invention, the housing part may have recesses on a surface on the radiation detector side. 
     Additionally, the cassette of the above aspect of the invention, the cassette further comprises a radiation shield plate that is provided on the side opposite to the radiation exposure side with respect to the radiation detector; and a support that is provided on the side opposite to the radiation exposure side with respect to the radiation shield plate, and that supports the radiation shield plate. The support may be fixed to the housing part. 
     Additionally, the cassette of the above aspect of the invention, the cassette further comprises a support that is provided on the side opposite to the radiation exposure side with respect to the radiation detector, and that supports the radiation detector. The support may be fixed to the housing part. The support and the housing part may directly face each other. 
     Additionally, the cassette of the above aspect of the invention, the material of the housing part may further contain Al. 
     Advantage of the Invention 
     According to the invention, a cassette having a transmission plate disposed on radiation exposure side and transmitting radiation, and a housing part disposed on opposite to the radiation exposure side, the cassette comprises a radiation detector that is disposed between the transmission plate and the housing part, in which material of the housing part contains 5 mass % or more and 25 mass % or less of Li can be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating the external appearance when an embodiment of a radiation detection cassette of the invention is seen from a radiation exposure side. 
         FIG. 2  is a perspective view illustrating the external appearance when the embodiment of the radiation detection cassette of the invention is seen from a side opposite to the radiation exposure side. 
         FIG. 3  is a view of the radiation detection cassette illustrated in  FIG. 2  as seen from arrow A direction. 
         FIG. 4  is a view of the radiation detection cassette illustrated in  FIG. 2  as seen from arrow B direction. 
         FIG. 5  is a perspective view of a back housing part formed of an alloy containing Mg and Li as seen from an inner surface (a surface on a radiation detector side) side. 
         FIG. 6  is a flowchart for explaining an embodiment of a method for manufacturing a housing of the radiation detection cassette of the invention. 
         FIG. 7  is a view illustrating an insertion screw provided in a female thread part. 
         FIG. 8  is a C-C line cross-sectional view of the radiation detection cassette illustrated in  FIG. 1 . 
         FIG. 9  is a cross-sectional view illustrating another embodiment of the radiation detection cassette of the invention. 
         FIG. 10  is a cross-sectional view illustrating still another embodiment of the radiation detection cassette of the invention. 
         FIG. 11  is a view illustrating an example of a radiation shield that is attachably and detachably configured with respect to the housing of the radiation detection cassette. 
         FIG. 12  is a cross-sectional view illustrating a schematic configuration around a recess formed in the back housing part. 
         FIG. 13  is a view illustrating still another embodiment of a frame body that constitutes the housing. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment of a method for manufacturing a housing of a radiation detection cassette of the invention will be described in detail, referring to the drawings. Although the invention has features in the method for manufacturing a housing of a radiation detection cassette, the configuration of a radiation detection cassette having a housing manufactured using the embodiment of the manufacturing method of the invention will first be described.  FIG. 1  is a perspective view illustrating the external appearance when the radiation detection cassette  1  having the housing manufactured by the manufacturing method of the present embodiment is seen from a radiation exposure side, and  FIG. 2  is a perspective view illustrating the external appearance when the radiation detection cassette  1  is seen from a side opposite to the radiation exposure side. Additionally,  FIG. 3  is a view of the radiation detection cassette  1  illustrated in  FIG. 2  as seen from arrow A, and  FIG. 4  is a view of the radiation detection cassette  1  illustrated in  FIG. 2  as seen from arrow B. 
     The radiation detection cassette  1  of the present embodiment includes a radiation detector  20 , and a housing  10  that houses the radiation detector  20 . 
     As illustrated in  FIGS. 1 to 4 , the housing  10  is formed in a rectangular shape, and includes a transmission plate  11  arranged on the radiation exposure side, a back housing part  12  having a surface portion opposite to the radiation exposure side, and a frame body  13 . 
     The transmission plate  11  is formed of a carbon material with a high transitivity of radiation, and is lightweight and high-rigidity. 
     The back housing part  12  is formed of an alloy containing Mg and Li and containing 0.1 mass % or more of Li. Since the alloy containing Mg and Li has a smaller specific gravity than an Mg alloy (Al 3%, Zn 1%, and Mg 96%) used as a material of a back housing part of the related-art radiation detection cassette, weight reduction of the radiation detection cassette  1  can be achieved. Additionally, the alloy containing Mg and Li has radiotransparency higher than the Mg alloy. Hence, generation of scattered radiation resulting from thickness structures, such as ribs formed on an inner surface (a surface on a radiation detector side) of the back housing part  12  can be suppressed. Accordingly, a radiation shield plate containing lead provided within the related-art radiation detection cassette to absorb the above scattered radiation can be thinned or omitted, and the weight reduction can be further achieved. As the alloy containing Mg and Li, for example, an alloy of 14 mass % of Li(s), 9 mass % of Al, and 77 mass % of Mg can be used. It is preferable that the content of Li is 5 mass % or more and 25 mass % or less. By making the content of Li be 25 mass % or less, manufacture can be made easy. Additionally, it is preferable that the content of Al is 1 mass % or more and 12 mass % or less. By making the content of Al be 1 mass % or more, corrosion resistance can be improved. Additionally, by making the content of Al be 12 mass % or less, the weight reduction can be achieved. 
     Additionally, as illustrated in  FIGS. 3 and 4 , the back housing part  12  has a side peripheral surface part  12   a  formed in a gentle inclined surface. By forming the side peripheral surface part  12   a  with an inclined surface In this way, for example, in a case where a radiation image of a subject that has lied oneself on a bed is captured, the radiation detection cassette  1  can be easily inserted between the subject and the bed. 
     Additionally,  FIG. 5  is a perspective view of the back housing part  12  formed of the alloy containing Mg and Li as seen from the inner surface (the surface on the radiation detector side) side. As illustrated in  FIG. 5 , recesses  12   f  of various shapes partitioned off by ribs  12   d  are formed on an inner surface side of the back housing part  12 . When such recesses  12   f  are formed, in the related art, the recesses  12   f  are formed by preparing a housing material in which no recesses  12   f  are formed and performing cutting work using an end mill or the like on the housing material. 
     However, in a case where the back housing part  12  is formed of the alloy containing Mg and Li, as described above, the alloy may deposit on a blade of the end mill, so that the recesses cannot be appropriately machined. Thus, in the method for manufacturing a housing  10  of the present embodiment, the recesses  12   f  are formed through a flow illustrated in a flowchart illustrated in  FIG. 6 . 
     First, a housing material that is formed of the alloy containing Mg and Li and contains 0.1 mass % or more of Li is prepared (S 10 ). Next, a rough recess pattern is formed by performing, for example, press working, such as hot pressing, on the surface of the housing material (S 12 ). 
     Then, final recesses  12   f  are shaped by performing cutting work using an end mill or the like, on the recess pattern formed by the press working (S 14 ). 
     According to the manufacturing method of an above embodiment, the rough recess pattern is shaped by performing the press working before the cutting work is performed. Thus, it is not necessary to carry out grooving in the subsequent cutting work, and the final recesses  12   f  are shaped by shouldering. Thus, the heat of the blade of the end mill can be dissipated. Accordingly, the recesses  12   f  can be appropriately shaped without the material depositing on the blade of the end mill. 
     In addition, in the present embodiment, the rough recess pattern is formed by performing the press working on the housing material before the cutting work. However, a working method before the cutting work is not limited to the press working, and the rough recess pattern may be formed using electrical discharge machining or casting, such as die casting. 
     Next, returning to  FIG. 2 , a battery housing part  12   b  in which a battery  16  that supplies electrical power to the radiation detector  20  is housed is formed in an outer surface of the back housing part  12 . The battery housing part  12   b  is provided by forming a recess in the outer surface of the back housing part  12 . In addition,  FIG. 2  illustrates a state where the battery  16  is housed in the battery housing part  12   b.    
     Additionally, female thread parts  12   c  are formed in the back housing part  12 . A male thread  17  is fitted into each female thread part  12   c,  and thereby, members, such as a support member, which is housed within the housing  10 , are fixed to the back housing part  12 . 
     Here, although the back housing part  12  of the present embodiment is formed of the alloy containing Mg and Li as described above, the alloy containing Mg and Li tends to corrode electrically. That is, in a case where a different kind of metal comes into contact with the alloy containing Mg and Li, the alloy containing Mg and Li with large ionization tendency corrodes if electrolytes, such as water, act. Since medical instruments are disinfected and sterilized, the medical instruments are exposed to various electrolytes, such as ethanol and peracetic acid, besides water, and electrical corrosion poses a problem. 
     Hence, it is desirable that the male thread  17  fitted into the female thread part  12   c  made of the alloy containing Mg and Li is made of nonmetal, such as resin or ceramics. 
     Additionally, a method of preventing the electrical corrosion of the female thread part  12   c  is not limited to this. For example, as illustrated in  FIG. 7 , a nonmetallic insertion screw  18  may be provided within the female thread part  12   c  such that the male thread is fitted into the insertion screw  18 . Accordingly, even if a metallic male thread  17  is used, the male thread can be prevented from coming into direct contact with the female thread part  12   c.  The insertion screw  18  is grooved in a hole so as to be engaged with the male thread  17 . 
     Otherwise, the processing of coating the inner surface of the female thread part  12   c  with a nonmetallic material may be performed. For example, in a case where chemical conversion treatment or the like is performed after the insertion screw  18  is inserted into the female thread part  12   c,  the electrical corrosion may occur between the female thread part  12   c  and insertion screw  18 . However, by performing coating processing on the inner surface of the female thread part  12   c  as described above, the electrical corrosion between the female thread part  12   c  and the insertion screw  18  can also be prevented. 
     The frame body  13  is made of a metallic frame of which four corners are subjected to round chamfering. The frame body  13  is configured so as to be engaged with a circumferential edge of the back housing part  12 . Additionally, the transmission plate  11  is fixed to the back housing part  12  by being engaged with the back housing part  12  in a state where the transmission plate  11  is fitted into the frame body  13 . 
     Additionally, as illustrated in  FIGS. 3 and 4 , female thread parts  13   a  are formed in the frame body  13 . Each female thread part  13   a  is formed through the frame body  13 , and a male thread  15  is fitted into the female thread part. The male thread  15  fitted into the female thread part  13   a  of the frame body  13  reaches the back housing part  12 , and is engaged with a female thread part (not illustrated) formed in the back housing part  12 . Accordingly, the frame body  13  into which the transmission plate  11  is fitted is fixed to and integrated with the back housing part  12 . In addition, in order to prevent the electrical corrosion resulting from contact with the female thread part of the back housing part  12 , it is desirable that the male thread  15  is also made of nonmetal, such as resin or ceramics. Additionally, the invention is not limited to this. However, as described above, an insertion screw  18  may be provided in the female thread part formed in the back housing part  12 , or coating processing may be performed on the inner surface of the female thread part formed in the back housing part  12 . 
       FIG. 8  is a C-C line cross-sectional view of the radiation detection cassette  1  of  FIG. 1 . In addition, the cross-sectional view illustrated in  FIG. 8  is a schematic view illustrating a schematic configuration of the radiation detection cassette  1 , and the sizes of respective parts are not accurate. 
     As illustrated in  FIG. 8 , an outer surface of the back housing part  12  is provided with a protective film  30 . In the present embodiment, as described above, the back housing part  12  is formed of the alloy containing Mg and Li. Accordingly, the weight reduction of the radiation detection cassette  1  can be achieved. On the other hand, however, since the radiation detection cassette  1  may be subjected to sterilization, disinfection, and the like or may be exposed to electrolyte solutions, such as a patient&#39;s blood, the corrosion resistance is required. The alloy containing Mg and Li is less resistant against corrosion than an Mg alloy containing no Li. Thus, in the present embodiment, the protective film  30  is provided as described above. Thus, improvement in the corrosion resistance can be achieved. 
     In addition, in the present embodiment, the entire outer surface of the back housing part  12  is provided with the protective film  30 . However, the invention is not limited to this, and a portion of the outer surface of the back housing part  12  may be provided with the protective film  30 . Specifically, the side peripheral surface part  12   a  of the back housing part  12  is a portion that comes into contact with a bed when the radiation detection cassette  1  is inserted between a subject and the bed. Hence, since the side peripheral surface part  12   a  of the back housing part  12 , that is, a peripheral part of the surface of the housing  10  opposite to the radiation exposure side is worn due to contact with the bed, scratch resistance is required. Hence, it is desirable to provide the protective film  30  at least on the side peripheral surface part  12   a  of the back housing part  12 . It is preferable that a range where the protective film  30  is provided is a range of 30 mm or more and 50 mm or less from a side end of the back housing part  12 . By providing the protective film  30  in such a range, the weight reduction can be achieved as compared to a case where the protective film  30  is provided on the entire outer surface of the back housing part  12 . Additionally, even in a case where the protective film  30  is provided on the entire outer surface of the back housing part  12 , it is preferable to make the thickness of the protective film  30  in the side peripheral surface part  12   a  of the back housing part  12  larger than the thickness of the protective film  30  provided in ranges other than the above range. 
     Additionally, in the radiation detection cassette  1  of the present embodiment, as illustrated in  FIG. 8 , the protective film  30  is continuously provided from the outer surface of the back housing part  12  to an outer surface  13   b  of the frame body  13 . The outer surface  13   b  of the frame body  13  on the radiation exposure side, that is, the peripheral part of the surface of the housing  10  on the radiation exposure side is a portion that comes into contact with a subject when the radiation detection cassette  1  is inserted between the subject and a bed. Therefore, since the outer surface  13   b  of the frame body  13  on the radiation exposure side is worn due to contact with the subject, the scratch resistance is required. Hence, it is desirable to provide the protective film  30  at least on the outer surface  13   b  of the frame body  13  on the radiation exposure side. It is desirable that the range where the protective film  30  is provided is provided in ranges other than a radiation detection region. Additionally, even in a case where the protective film  30  is provided on the entire outer surface  13   b  of the frame body  13  continuously from the outer surface of the back housing part  12 , it is preferable to make the thickness of the protective film  30  in the outer surface  13   b  of the frame body  13  larger than the thickness of the protective film  30  provided in the other ranges. 
     As the protective film  30 , it is desirable to use a resin sheet. The resin sheet has easy handling and pasting. As the resin sheet, for example, polyvinyl chloride sheets can be used. However, the protective film  30  is not limited to this. For example, the protective film  30  may be formed by performing phosphoric-acid-based or chromium-based chemical conversion treatment. Otherwise, the protective film  30  may be formed by plating, such as electroless plating or the like, or the protective film  30  may be formed by painting, such as solvent painting and powder coating. Additionally, in order to further improve the corrosion resistance, the protective film  30  may be made to contain Al. 
     Next, a schematic configuration within the housing  10  of the radiation detection cassette  1  will be described, referring to  FIG. 8 . As illustrated in  FIG. 8 , the radiation detector  20 , a radiation shield plate  40 , and a support  50  are provided within the housing  10  of the radiation detection cassette  1 . 
     The radiation detector  20  is a rectangular detector that detects radiation transmitted through a subject. The radiation detector  20  of the present embodiment includes a scintillator layer (phosphor layer)  21  that converts incident radiation into visible light, and a thin film transistor (TFT) active matrix substrate  22  that photoelectrically converts of visible light emitted from the scintillator layer  21  to output radiation image signals. A rectangular imaging region where a plurality of pixels that accumulate electric charge according to the visible light from the scintillator layer  21  are arrayed is formed on the TFT active matrix substrate  22 . In addition, in the present embodiment, the TFT active matrix substrate  22  and the scintillator layer  21  are arranged in this order from the radiation exposure side illustrated by arrow X in  FIG. 8 . However, the invention is not limited to this. Conversely, the scintillator layer  21  and the TFT active matrix substrate  22  are arranged in this order from the radiation exposure side. 
     Additionally, in addition to the radiation detector  20 , an imaging control unit including a gate driver that gives a gate pulse to a gate of a TFT to switch the TFT, a signal processing circuit that converts an electric charge accumulated in a pixel to an analog electrical signal representing a radiation image to output the converted signal, and the like is provided within the housing  10 . 
     Additionally, in the present embodiment, a so-called indirect conversion type radiation detector  20  that performs photoelectric conversion after radiation is first converted into visible light is used as the radiation detector  20 . However, a so-called direct conversion type radiation detector that directly converts radiation into an electric charge signal may be used. Additionally, in the present embodiment, a so-called TFT reading type radiation detector using the TFT active matrix substrate  22  is used. However, the invention is not limited to this. A so-called optical reading type radiation detector that accumulates an electric charge with irradiation of radiation first and reads the stored charge with irradiation of excitation light to acquire a radiation image signal may be used. 
     The radiation shield plate  40  is provided on the side opposite to the radiation exposure side with respect to the radiation detector  20  within the housing  10 , and is formed from a plate-like member containing lead with a thickness of more than 0 mm and less than 0.1 mm. 
     The radiation shield plate  40  absorbs the scattered radiation resulting from the thickness structures, such as ribs  12   d  formed on the inner surface of the back housing part  12 . In the present embodiment, since the back housing part  12  is formed of the alloy containing Mg and Li as described above, the generation of the scattered radiation itself can be suppressed. Hence, the radiation shield plate  40  can be made thinner than that in the related art, and the weight reduction can be achieved. In addition, in the present embodiment, lead is used as the material of the radiation shield plate  40 . However, the invention is not limited to this. Other radiation absorbent materials, such as Steel Use Stainless (SUS), iron, and tungsten, may be used. 
     The radiation shield plate  40  and the radiation detector  20  are bonded together, for example, using an adhesive tape or the like. 
     The support  50  supports the radiation detector  20  and the radiation shield plate  40 , and is formed of a carbon material that allows radiation to be transmitted through. The support  50  of the present embodiment is fixed to the back housing part  12 , and thereby, the radiation detector  20  and the radiation shield plate  40  are fixed to the back housing part  12 . 
     In addition, in the present embodiment, the radiation shield plate  40  is provided as described above. However, the radiation shield plate  40  may be omitted. That is, as illustrated in  FIG. 9 , the support  50  and the inner surface of the back housing part  12  directly face each other without providing the radiation shield plate  40 . In addition, the support  50  and the inner surface of the back housing part  12  directly facing each other means that other members are not present between the support  50  and the inner surface of the back housing part  12 . 
     Additionally, the configuration in which the radiation shield plate  40  is not provided is not limited to the configuration illustrated in  FIG. 9 . As illustrated in  FIG. 10 , the support  50  may be fixed to the transmission plate  11  side and the radiation detector  20  may be provided at the support  50  such that the radiation detector  20  and the inner surface of the back housing part  12  directly face each other. In addition, the radiation detector  20  and the inner surface of the back housing part  12  directly facing each other means that other members are not present between the radiation detector  20  and the inner surface of the back housing part  12 . Additionally, even in the configuration illustrated in  FIGS. 7 and 8 , the arrangement of the scintillator layer  21  and the TFT active matrix substrate  22  may be reversed. 
     Additionally, in the radiation detection cassette  1  of the present embodiment, as illustrated in  FIG. 8 , a waterproof structure  70  may be provided in a gap of a portion where the circumferential edge of the back housing part  12  and the frame body  13  are engaged with each other. As the waterproof structure  70 , for example, rubber packing can be used. The rubber packing is crushed by the engagement between the circumferential edge of the back housing part  12  and the frame body  13 , so that liquid-tight sealing can be made, and liquids, such as water, ethanol, and peracetic acid, which are used for disinfection and sterilization can be prevented from entering the housing  10 . 
     Additionally, in a case where the radiation detection cassette  1  of the above embodiment is installed and used on a bed or is installed and used on an imaging stand for standing position imaging, the radiation transmitted through the radiation detection cassette  1  may be reflected to structures, such as the bed or the imaging stand, to enter the radiation detector  20  within the radiation detection cassette  1 , and an artifact may be generated. Hence, in order to prevent the generation of such an artifact, a radiation shield  60  containing lead may be provided at a position on the side opposite to the radiation exposure side of the radiation detection cassette  1 . 
     It is preferable that this radiation shield  60  is made attachable and detachable with respect to the housing  10 . By adopting such a configuration, the radiation shield  60  can be attached to the housing  10  if necessary. In a case where there is no necessity, by detaching the radiation shield  60  from the housing  10 , the weight reduction of the radiation detection cassette  1  can be achieved, and carrying is also easy. 
       FIG. 11  is a view illustrating an example of a radiation shield  60  that is attachable to and detachable from the housing  10 . The radiation shield  60  includes a radiation shield plate  62  containing lead, a housing part  61  in which the radiation shield plate  62  is housed, and an attachment member  63 . In addition, a direction of arrow X illustrated in  FIG. 11  is a radiation exposure direction. 
     As the radiation shield plate  62 , for example, a plate made of lead and having a thickness of 0.5 mm in the radiation exposure direction can be used. In addition, radiation absorbent materials such as a plate made of SUS and having a thickness of 1.5 mm in the radiation exposure direction, a plate made of tungsten and having a thickness of 1.5 mm in the radiation exposure direction, or a plate made of iron and having a thickness of 2.0 mm in the radiation exposure direction can be used. 
     Attachment members  63  are respectively provided on sides that faces the housing part  61 . Each attachment member  63  is turned in a direction of arrow D about a turning shaft  63   a.  Each attachment member  63  is engaged with each of the sides that face the housing  10  of the radiation detection cassette  1 , and thereby, the radiation shield  60  is attached to the housing  10  of the radiation detection cassette  1 .  FIG. 9  illustrates a state where the radiation shield  60  is attached to the housing  10 , and illustrates a state of the attachment members  63  in a case where the radiation shield  60  is detached from the housing  10 , by a dotted line. 
     By attaching the attachment members  63  to the radiation shield  60  side like a configuration illustrated in  FIG. 11 , it is not necessary to perform special processing on the housing  10  of the radiation detection cassette  1 . Hence, since it is possible to be attached to any type of housing  10  if the size of the radiation shield  60  matches the size of the housing  10 , it is not necessary to customize the radiation detection cassette  1 , and reduction of cost can be achieved. However, as the configuration in which the radiation shield  60  is attachable and detachable, the invention is not limited to the configuration illustrated in  FIG. 11 , and other configurations may be adopted. 
     Additionally, as a method of suppressing the artifact resulting from the radiation being reflected due to the bed, the imaging stand, or the like, the protective film  30  may be made to contain lead, and the protective film  30  may be made to absorb the radiation reflected due to the bed, the imaging stand, or the like. In this case, it is preferable that the thickness of the protective film  30  is about 0.2 mm, and it is preferable that lead contains about 50 mass %. 
     Additionally, in the radiation detection cassette  1  of the above embodiment, the protective film  30  is provided in order to give the corrosion resistance and the scratch resistance as described above. However, it is still more preferable to make the protective film  30  has a fireproof enclosure function. Specifically, it is preferable that the protective film  30  contains at least one of Ca, B, and metal. For example, in a case where the resin sheet is used as the protective film  30 , a resin sheet containing at least one of Ca (calcium), B (boron), and the metal may be used. Otherwise, in a case where a paint film is used as the protective film  30 , metal may be contained in a paint material. As the metal contained in the protective film  30 , there is, for example, Ca or the like. 
     Additionally, in a case where the protective film  30  is made to have the fireproof enclosure function as described above, it is desirable to provide the protective film  30  on the entire outer surface of the back housing part  12 . However, in the radiation detection cassette  1  of the present embodiment, the battery housing part  12   b  where a battery is housed is formed in the back housing part  12  as described above. Thus, for example, in a case where the resin sheet is used as the protective film  30 , it is difficult to laminate the resin sheet uniformly within the battery housing part  12   b  and at the peripheral part of the battery housing part  12   b.    
     Then, it is preferable to laminate separate resin sheets within the battery housing part  12   b  and at the peripheral part of the battery housing part  12   b.    FIG. 12  is a view illustrating a sectional view, taken along arrow E-E line, of the battery housing part  12   b  and its peripheral part of the radiation detection cassette  1  illustrated in  FIG. 2 . In addition, in  FIG. 12 , the battery  16  installed within the battery housing part  12   b  is not illustrated. As illustrated in  FIG. 12 , it is preferable to provide a first protective film  31  at the peripheral part of the battery housing part  12   b  and provide a second protective film  32  at a bottom part of the recess. It is preferable that a gap d 1  between an end part  31   a  of the first protective film  31  and an end part  32   a  of the second protective film  32  adjacent to the end part  31   a  is more than 0 mm and 2 mm or less. Otherwise, the end part  31   a  of the first protective film  31  and an end part  32   a  of the second protective film  32  may be made to overlap each other as seen from the side opposite to the radiation exposure side. 
     Additionally, for the weight reduction of the back housing part  12 , as illustrated in  FIG. 12 , it is preferable to form an opening  12   e  at the bottom part of the battery housing part  12   b.  Since the opening  12   e  being provided in this way is not good from a viewpoint of electro-magnetic compatibility (EMC), in the related-art radiation detection cassette, this opening is not provided, or the opening is needed to be closed using a sheet member. 
     In contrast, in the radiation detection cassette  1  of the present embodiment, the alloy containing Mg and Li is used as a material of the back housing part  12 . Thus, EMC is improved compared to a case where the related-art Mg alloy is used. Hence, it is not necessary to provide the sheet member as in the related-art radiation detection cassette, and as illustrated in  FIG. 12 , a medium plate  80  serving as the support member can be arranged near the opening  12   e.  The medium plate  80  is formed of metal. It is preferable that a gap d 2  between the opening  12   e  and the medium plate  80  is more than 0 mm and 2 mm or less. 
     Additionally, the alloy of the back housing part  12  instead of the protective film  30  may be made to contain Ca. It is preferable that the content of Ca is 0.3 mass % or more and 7 mass % or less. By making the content of Ca be 0.3 mass % or more, flame retardance can be improved. Additionally, the weight reduction can be achieved by making the content of Ca be 7 mass % or less. As the alloy containing Ca, for example, an alloy of 14 mass % of Li, 9 mass % of Al, 1 mass % of Ca, and 76 mass % of Mg can be used. 
     Additionally, both the alloy of the back housing part  12  and the protective film  30  may be made to contain Ca. 
     Additionally, it is preferable that the radiation detection cassette  1  of the above embodiment includes the frame body  13 . However, as illustrated in  FIG. 13 , it is preferable that the frame body  13  is formed so as to protrude further outward than a position (a position illustrated by a dotted line in  FIG. 13 ) at a side end of the back housing part  12  as seen from the radiation exposure side. By adopting such a configuration, for example, the impact resistance when the radiation detection cassette  1  has fallen on the ground can be improved. 
     Additionally, as a method of improving the impact resistance of the radiation detection cassette  1 , in a case where the protective film  30  is formed of the paint film, it is preferable that a cushioning property is provided by making the paint thickness be 50 μm or more. Additionally, two or more layers of paint films may be formed, and the total thickness thereof may be 50 μm or more. Additionally, in a case where the resin sheet is used as the protective film  30 , it is preferable to use a resin sheet of 50 μm or more. 
     Additionally, regarding the protective film  30  of the radiation detection cassette  1  of the above embodiment, it is preferable to perform water-repellent coating processing or water-repellent painting. Accordingly, the corrosion resistance can be further improved. 
     Explanation of References 
     
         
         
           
               1 : radiation detection cassette 
               2 : radiation detector 
               10 : housing 
               11 : transmission plate 
               12 : back housing part 
               12   a:  side peripheral surface part 
               12   b:  battery housing part 
               12   c:  female thread part 
               12   d:  rib 
               12   e:  opening 
               12   f:  recess 
               13 : frame body 
               13   a:  female thread part 
               13   b:  outer surface 
               15 : male thread 
               16 : battery 
               17 : male thread 
               18 : insertion screw 
               20 : radiation detector 
               21 : scintillator layer 
               22 : active-matrix substrate 
               30 : protective film 
               31 : first protective film 
               31   a:  end part 
               32 : second protective film 
               32   a:  end part 
               40 : radiation shield plate 
               50 : support 
               60 : radiation shield 
               61 : housing part 
               62 : radiation shield plate 
               63 : attachment member 
               63   a:  turning shaft 
               70 : waterproof structure 
               80 : medium plate 
             d 1 : gap 
             d 2 : gap