Abstract:
A radiation image photographing apparatus configured to detect radiation includes a radiation detecting panel configured to convert received radiation into an electrical signal, and a support substrate configured to support the radiation detecting panel. In addition, a housing is configured to contain the radiation detecting panel and the support substrate. A plurality of openings are formed on a side of a surface of the support substrate, with the surface being opposite to a surface of the support substrate configured to support the radiation detecting panel.

Description:
[0001]     This application is a divisional of application Ser. No. 10/812,867, filed Mar. 31, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a radiation digital image photographing apparatus for photographing a radiation image by the use of a digital signal.  
         [0004]     2. Related Background Art  
         [0005]     Conventionally, an apparatus for obtaining a radiation image of an object by illuminating the object with radiation and detecting a distribution of the intensity of radiation transmitted through or penetrating the object has been widely used in the fields of medical diagnosis and non-destructive inspection for industry, etc. A film/screen method for radiation is known as a general method for effecting such photographing. This method is a method for effecting photographing under a condition in which a photosensitive film is combined with a fluorescent material sensitive to radiation. In this method, a sheet-shaped fluorescent member of rare-earth element capable of light emission upon its illumination with radiation is in close contact with and held on each of opposite surfaces of the photosensitive film, radiation transmitted through the object is converted into visible light by the fluorescent member, the light is captured by the photosensitive film, and a latent image formed on the film is developed by chemical treatment and visualized.  
         [0006]     On the other hand, owing to recent advance of digital technology, use is made of a method in which after a radiation image is converted into an electrical signal and the electrical signal is image-processed, the thus-processed image is reproduced as a visible image on a CRT or the like, thereby obtaining a high-quality radiation image. In connection with such a method for converting the radiation image into the electrical signal, Japanese Patent Application Laid-Open Nos. H55-12429 and H56-11395, for example, disclose a radiation image recording and reproducing system in which after a radiation transmission image is once stored in a fluorescent member as a latent image, the fluorescent member is illuminated with stimulated light, such as laser light, to photoelectrically read the latent image, thereby outputting a visualized image of the radiation transmission image.  
         [0007]     Further, as semiconductor process technology advances of late, there has been developed an apparatus for photographing a radiation image in a similar manner using a semiconductor sensor. Such a kind of system has a very wide dynamic range, and is capable of obtaining a radiation image that is unlikely to be influenced by fluctuation of the exposure amount of radiation, as compared with a conventional radiation photographing system which uses a photosensitive film. Further, no chemical treatment is needed, and an output image can be instantaneously obtained, differently from the conventional photosensitive film system.  
         [0008]     Such a kind of photographing apparatus is generally settled and used in a radiation room, and its rigidity has been so far considered more important than the weight and size in a thickness direction of the radiation image photographing apparatus itself.  
         [0009]     In recent years, however, a portable photographing apparatus, such as a so-called electronic cassette, is desired for the purposes of attaining speedy and wide-range photographing. Further, it is required in the light of advantages in the cost to establish a system in which a single photographing apparatus is mounted to a plurality of photographing supports at the same time to enable photographing of various portions.  
         [0010]     In this case, it is desirable for operators, such as radiographic engineers, that the electronic cassette is light in weight, considering the operators&#39; works in settling the electronic cassette at a predetermined location and transporting the electronic cassette. Further, if the size in the thickness direction of the electronic cassette is large, an object person is liable to be pained in the event that the electronic cassette is inserted into a spacing between the object person lying on a bed and the bed.  
         [0011]     However, if the weight and thickness of the electronic cassette are reduced, a problem of reduction of its mechanical strength occurs. Furthermore, there is a possibility that some radiation penetrates the apparatus and goes outside, is then scattered by a wall, a floor and the like behind the apparatus, returns from behind the apparatus, and is finally input into a sensor in the apparatus. It is necessary to oppress such scattered radiation from behind the apparatus as much as possible, since such radiation can cause a difference in transmittance between parts of a structure in the photographing portion to be photographed in an image as a flare.  
         [0012]     As discussed in the foregoing, a variety of appropriate measures have been desired to cope with enlarged thickness and increased weight of conventional radiation image photographing apparatuses.  
       SUMMARY OF THE INVENTION  
       [0013]     It is an object of the present invention in view of the above-discussed problem to provide a radiation image photographing apparatus capable of being reduced in its thickness and weight, for example.  
         [0014]     A radiation image photographing apparatus according to the present invention is directed to a radiation image photographing apparatus in which an object is irradiated with radiation emitted from a radiation generating unit, and a distribution of radiation penetrating the object is detected by a sensor. The radiation image photographing apparatus includes a radiation detecting panel having a detection surface on which there is arranged an optoelectrical converting device for detecting radiation penetrating the object, a support substrate for supporting the radiation detecting panel, and a housing for containing the radiation detecting panel and the support substrate. The radiation detecting panel, the support substrate, and the housing constitute a photographing portion. A surface of the support substrate for supporting the radiation detecting panel is made flat, and a recess portion having a plurality of openings are formed on a side of a surface of the support substrate, which is opposite to the surface of the support substrate for supporting the radiation detecting panel in a thickness direction. A reinforcing plate is fixed such that those recess portions can be covered therewith.  
         [0015]     Other objects, features and advantages of the present invention will be apparent from the following descriptions taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the descriptions, serve to explain the principle of the invention.  
         [0017]      FIG. 1  is a conceptual view schematically illustrating a general system;  
         [0018]      FIG. 2  is a side cross-sectional view illustrating a first embodiment according to the present invention;  
         [0019]      FIG. 3  is a cross-sectional view taken from a bottom side;  
         [0020]      FIG. 4  is a side cross-sectional view illustrating a second embodiment according to the present invention;  
         [0021]      FIG. 5  is a side cross-sectional view illustrating a third embodiment according to the present invention;  
         [0022]      FIG. 6  is a side cross-sectional view illustrating a fourth embodiment according to the present invention; and  
         [0023]      FIG. 7  is a side cross-sectional view illustrating a fifth embodiment according to the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     Embodiments of the present invention will be described in detail hereinafter with reference to the drawings.  
         [0025]      FIG. 1  is a conceptual view schematically illustrating a general system using such a radiation image photographing apparatus. A radiation detecting unit  2  is built in a radiation image photographing apparatus  1 . A radiation generating apparatus  3  is disposed above the radiation image photographing apparatus  1 . An object S is illuminated with radiation emitted from the radiation generating apparatus  3 , and radiation transmitted through the object S is detected by the radiation detecting unit  2  with a two-dimensional grid-like arrangement. An image signal output from the radiation detecting unit  2  is image-processed in a digital manner by an image processing unit  4 , and a radiation image of the object S is displayed on a monitor  5 .  
         [0026]      FIG. 2  is a cross-sectional view illustrating the radiation image photographing apparatus  1  of the first embodiment, and  FIG. 3  is a cross-sectional view taken from a bottom side of the radiation image photographing apparatus  1 . An upper portion of a lower housing  11   a  is sealed by an upper housing  11   b  formed of Carbon Fiber Reinforced Plastic (CFRP) which is excellent in its X-ray transmittance and physical strength. A plurality of holes  12  for setting a screw are formed at plural locations on the bottom surface of the lower housing  11   a . A screw  13  is inserted in the screw setting hole  12 , and a support member  14  is mounted thereby. On the support members  14 , a support substrate  15  is settled. The support substrate  15  is comprised of a highly-rigid structure formed of aluminum alloy, magnesium alloy, or the like, which is light in weight and highly strong such that the structure can be protected against vibrations, shocks and so forth at the time of transportation. A radiation image detecting panel  16  is fixed to the support substrate  15  by a thin bonding layer, such as a double adhesive tape and an adhesive agent.  
         [0027]     The radiation image detecting panel  16  is constructed by layering from an upper side a fluorescent member  16   a  for converting radiation into visible light, a grid-shaped optoelectric converting device  16   b  for converting the visible light into an electrical signal, and a substrate  16   c  on a surface of which the optoelectric converting device  16   b  is arranged. A glass substrate is often used as the substrate  16   c  because of necessities that it must have no chemical reaction with a semiconductor device, that it must be resistant to temperatures of semiconductor forming process, and that its size must be stable. The optoelectric converting device  16   b  is formed on the glass substrate  16   c  in a two-dimensional arrangement by a semiconductor process, and the fluorescent member  16   a  is comprised of a resin plate which is coated with a fluorescent material of metal compound.  
         [0028]     The optoelectric converting device  16   b  is connected through a flexible circuit board  17  to a circuit board  18  which is equipped with electronic components  18   a  and  18   b  for processing the optoelectrically converted electrical signal, or controlling the drive of the radiation image detecting panel  16 . Further, a space extending in a thickness direction is formed between the support substrate  15  and the lower housing  11   a  such that a relatively tall electrical component  18   b , such as a capacitor, can be arranged on the circuit board  18 . It is, however, possible to prevent an increase of the space in the thickness direction by forming a space around the side of the support member  14 .  
         [0029]     It is required for the upper housing  11   b  to have as high a radiation transmittance as possible such that a high S/N can be obtained without lowering the amount of radiation to be detected. On the other hand, however, the radiation detecting panel  16  needs to be protected in the event that the object rides on the upper housing  11   b . For that purpose, it is required that the thickness of the radiation image photographing apparatus  1  itself be increased to improve its rigidity, or an appropriate distance be established between the radiation detecting panel  16  and the upper housing  11   b . Considering those conditions, it is difficult to support load only by the upper housing  11   b  such that any stress cannot be applied on the radiation detecting panel  16 , without any decrease in the radiation transmittance and any increase in the external size of the radiation image photographing apparatus  1 . Accordingly, it is necessary to provide a load supporting structure which is resistant to load, even if the load is applied on the radiation detecting panel  16  itself.  
         [0030]     An upper surface  15   a  of the support substrate  15  for mounting the radiation detecting panel  16  thereto is made flat such that the load will not be borne only by the radiation detecting panel  16 . The strength of the support substrate  15  is designed such that a bending stress imposed on the radiation detecting panel  16  can fall within an allowable range even when the load is applied on the support substrate  15  from above.  
         [0031]     Further, a buffer material  19  is interposed between the upper housing  11   b  and the radiation detecting panel  16 , so that occurrence of a local stress on the radiation detecting panel  16  can be oppressed and dispersion of stress can be achieved by the buffer material  19  even in the event that the load is imposed on the upper housing  11   b  and the upper housing  11   b  is hence flexed.  
         [0032]     A plurality of recess portions  15   c  with openings are formed on the side of a lower surface  15   b  of the support substrate  15 . And, a planar reinforcing plate  20  is fixed such that those recess portions  15   c  can be covered therewith. The reinforcing plate  20  is formed of a material having high elastic coefficient and light weight, such as fiber-reinforced plastics, fiber-reinforced metal, and aluminum alloy.  
         [0033]     As illustrated in  FIG. 3 , the recess portions  15   c  are arranged with the same shape at sections of the support substrate  15  defined by alternate long and short dash lines, respectively. The reinforcing plate  20  is fixed at corners of each section, and the support member  14  for supporting the load is mounted to each corner of each section. The reinforcing plate  20  is fixed by the use of fastening by the support member  14  and bonding to the surface  15   b . The support member  14  is brought into contact with the inner surface of the lower housing  11   a , and some of the support members  14  are fastened by the screws  13 , respectively, as described above.  
         [0034]     Thus, extension occurring due to the bending can be oppressed by the arrangement of the reinforcing plate  20 , and load resistant capability achieved thereby can be enhanced more than that obtained by the structure having the recess portions  15   c  only. Further, although its strength is lower than a substrate  15  having a uniform thickness and lacking the recess portion  15   c , the strength can be compensated for by shortening the distance between the support points and increasing the number of escapes for the support members  14  formed in the circuit board  18 .  
         [0035]     When a thick portion  15   d  is formed on the side of the upper surface  15   a  of the support substrate  15  as discussed above, occurrence of its deformation due to the local load can be made difficult, and at the same time the thick portion  15   d  can effectively serve as an electromagnetic-wave shielding material for the radiation detecting panel  16 . Moreover, since the reinforcing plate  20  is mounted to the side of the lower surface  15   b , but not to the side of the upper surface  15   a , the fastening by the screw can be used as well as the bonding. Accordingly, the reinforcement can be effectively achieved. Owing to the use of such a reinforcing plate, it is thus possible to construct the support substrate for supporting the radiation detecting panel as a hollow structure, and achieve a thin and light apparatus. Resultantly, the load imposed on the operator and the object can be reduced, and operational conditions for the operator are improved and discomfort of the object is lightened.  
         [0036]      FIG. 4  is a cross-sectional view illustrating a second embodiment of the present invention, in which like reference characters designate the same or similar parts of the first embodiment. In the second embodiment, an opening  20   a  is formed in a portion of the reinforcing plate  20  near the periphery of the support substrate  15  in which possibility of load imposition is small. Through the opening  20   a , inserted into the recess  15   c  is a relatively tall electrical component  18   b  placed on the circuit board  18 , such as a capacitor.  
         [0037]     It is hence possible to shorten the size in the thickness direction, i.e., the distance between the support substrate  15  and the lower housing  11   a , without largely changing the load resistant capability. The radiation image photographing apparatus can be thus made thin.  
         [0038]     Further, the support substrate for supporting the radiation detecting panel can be constructed as a hollow structure because of the presence of the reinforcing plate, and the electrical circuit component can be contained in such a hollow portion, so that the apparatus can be thinned and lightened. Resultantly, the load imposed on the operator and the object can be reduced, and operational conditions for the operator are improved and discomfort of the object is lightened.  
         [0039]      FIG. 5  is a cross-sectional view illustrating a third embodiment of the present invention. In the third embodiment, plural sensors  21  are arranged in a divided manner in some of the recess portions  15   c  formed in the lower portion of the support substrate  15 . Those sensors  21  detect the amount of irradiated X-rays, control the X-ray generating apparatus, detect the end of X-ray irradiation, or start the reading of data from the radiation detecting panel  16 . The sensors  21  are connected to the circuit board  18  through connecting wires  22  and connectors  23 , respectively.  
         [0040]     In the third embodiment, through-holes for the connecting wire  22  only need to be formed in the reinforcing plate  20 . Accordingly, the reinforcing plate  20  can be advantageously made thin without weakening its physical strength. Sufficiently large electrical signals can be obtained by compounding outputs from the plural sensors  21  on the circuit.  
         [0041]     It is hence possible to construct the support substrate for supporting the radiation detecting panel as a hollow structure owing to the presence of the reinforcing plate, and contain the sensor for monitoring X-rays in such a hollow portion, so that the apparatus can be thinned and lightened. Resultantly, the load imposed on the operator and the object can be reduced, and operational conditions for the operator are improved and discomfort of the object is lightened.  
         [0042]      FIG. 6  is a cross-sectional view illustrating a fourth embodiment of the present invention. In the fourth embodiment, another reinforcing plate  24  is interposed between the radiation detecting panel  16  and the support substrate  15 . The reinforcing plate  24  is fixed since it serves as a means for correcting warps of the reinforcing plate  20  and the support substrate  15 . It is, however, desirable to mount the reinforcing plate  24  to the radiation detecting panel  16  through a soft bonding layer such that stress can readily escape.  
         [0043]     In this case, it is preferable to make the warp-correcting reinforcing plate  24  of fiber-reinforced plastics equivalent to that of the reinforcing plate  20 , or material equivalent to linear expansion coefficient with respect to order of magnitude of the reinforcing plate  20  for reinforcement. The linear expansion coefficient of CFRP used for the reinforcing plate  20  is about 2×10 −6 /° C., and so it is desirable to make the warp-correcting reinforcing plate  24  of a material having the linear expansion coefficient of about n×10 −6 /° C. The linear expansion coefficient of aluminum alloy or magnesium alloy used for the support substrate  15  is about 2×10 −5  to 3×10 −5 /° C., and this value is different by one order from the above value. In the event that the reinforcing plate  24  is made of tungsten, tantalum or molybdenum, the linear expansion coefficient thereof is small, for example, about 4×10 −6  to 6×10 −6 /° C.  
         [0044]     Owing to such a structure, large warp is unlikely to appear even when the ambient temperature is in a range of 20° C.±40° C., and a large bending stress can be prevented from occurring in the radiation detecting panel  16 .  
         [0045]     On the other hand, tungsten, tantalum and molybdenum are all heavy metals, and their weights are much larger than that of CFRP. However, since they are all heavy metals, their radiation shielding capabilities are high. Accordingly, each of those heavy metals can be used as a shielding means for shielding rays scattered from behind the radiation detecting panel  16 . When such a reinforcing plate for correcting thermal expansion is used as a means for preventing the warp, reduction of weight and reliability of environmental resistance can be both achieved.  
         [0046]     Furthermore, in the event that heavy metal is employed as the reinforcing plate, the radiation shielding function can also be obtained, and the apparatus can be simplified in its construction, and be somewhat lightened, as compared with a conventional construction with an externally-mounted leaden plate.  
         [0047]     Radiation cannot be all absorbed by the fluorescent member  16   a , and a portion thereof penetrates the apparatus, and goes outside the apparatus. When such radiation penetrating the apparatus is scattered by the wall, the floor and the like behind the apparatus, it returns from behind the apparatus, and becomes unwanted input which is to be photographed as an image of a structure such as the support substrate  15 . To shield such unwanted radiation, it is necessary to arrange a radiation shielding member covering the overall radiation detecting panel  16  therewith, and construct its structure without any slight openings.  
         [0048]      FIG. 7  is a cross-sectional view illustrating a fifth embodiment of the present invention. In the fifth embodiment, a recess portion  25  is formed over the entire lower surface of the lower housing  11   a , the recess portion  25  is lined with a plate-shaped radiation shielding member  26 , and the radiation shielding member  26  is covered with an external cover  27 , such that the radiation shielding need not depend on inner structures of the support substrate  15  and the lower housing  11   a . The radiation shielding member  26  is formed of lead which is generally available at a relatively cheap cost.  
         [0049]     As described in the foregoing, the radiation image photographing apparatus according to the present invention can be reduced in its thickness and weight.  
         [0050]     The present invention is not limited to the above embodiments, and various changes and modifications can be made within the spirit and scope of the present invention. Therefore to apprise the public of the scope of the present invention, the following claims are made.