Patent Publication Number: US-2013230142-A1

Title: X-ray imaging apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an X-ray imaging apparatus. Specifically, the present invention relates to an X-ray imaging apparatus including an X-ray tube, a storing unit for storing an X-ray reception unit, and a control unit for controlling the X-ray tube, which are supported by the same arm unit. 
     2. Description of the Related Art 
     In recent years, an X-ray imaging apparatus for the purpose of medical diagnosis or the like has been used for emergency treatment or medical care at home because of its enhanced portability due to downsizing and weight reduction of an X-ray generator including the X-ray tube. 
     Japanese Patent Application Laid-Open No. 2011-56170 discloses a technology in which an X-ray tube is used while suspended vertically above a part of a subject to be inspected by a holding fixture of an assembly type. However, the X-ray imaging apparatus disclosed in Japanese Patent Application Laid-Open No. 2011-56170 has the problem that it requires time and effort to assemble and install the holding fixture prior to radiography being performed. In addition, the X-ray tube and the holding fixture are separate members, and hence there is also a problem in that the portability itself is poor. 
     Japanese Patent Application Laid-Open No. 2010-57546 discloses a structure in which an X-ray tube and the holding fixture are integrated. According to the structure described in Japanese Patent Application Laid-Open No. 2010-57546, an X-ray imaging apparatus can be quickly installed. However, the X-ray reception unit (X-ray detector) is still a separate member. Therefore, in order to arrange the X-ray tube vertically above the part of a body to be inspected it is necessary to turn on an illumination lamp for illuminating a range equivalent to the X-ray radiation range and to adjust the position of the X-ray tube so that the part of the body to be inspected is placed within the radiation field. In this way, the structure described in Japanese Patent Application Laid-Open No. 2010-57546 has the problem in that it is difficult to perform radiography quickly. 
     SUMMARY OF THE INVENTION 
     An X-ray imaging apparatus includes: an X-ray generation unit for radiating an X-ray; a control unit for controlling the X-ray generation unit; an X-ray reception unit; a storing unit capable of storing the X-ray reception unit for receiving the X-ray radiated from the X-ray generation unit; and a U-shaped arm unit formed of a rod-like member, for holding the X-ray generation unit, the control unit, and the storing unit. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. Each of the embodiments of the present invention described below can be implemented solely or as a combination of a plurality of the embodiments or features thereof where necessary or where the combination of elements or features from individual embodiments in a single embodiment is beneficial. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view schematically illustrating a structure of a main part of an X-ray imaging apparatus according to a first embodiment of the present invention. 
         FIG. 2  is a block diagram schematically illustrating a system configuration of the X-ray imaging apparatus according to the first embodiment of the present invention. 
         FIG. 3  schematically illustrates a relationship among an X-ray generation unit, a storing unit, a control unit, and an arm unit. 
         FIG. 4  is a plan view of the X-ray imaging apparatus according to the first embodiment of the present invention viewed from the above. 
         FIG. 5  schematically illustrates the X-ray imaging apparatus according to the first embodiment of the present invention in a state of being installed in a sideways posture. 
         FIG. 6  is a flowchart illustrating an example of a process of the X-ray imaging apparatus according to the first embodiment of the present invention. 
         FIG. 7  is a block diagram schematically illustrating a system configuration of an X-ray imaging apparatus according to a second embodiment of the present invention. 
         FIG. 8  is a flowchart illustrating an example of a process of the X-ray imaging apparatus according to the second embodiment of the present invention. 
         FIG. 9  is a block diagram schematically illustrating a system configuration of an X-ray imaging apparatus according to a third embodiment of the present invention. 
         FIG. 10  is a block diagram schematically illustrating a system configuration of an X-ray imaging apparatus according to a fourth embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment  
       FIG. 1  schematically illustrates a structure of a main part of an X-ray imaging apparatus  101   a  according to a first embodiment of the present invention.  FIG. 2  is a block diagram illustrating a system configuration of the main part of the X-ray imaging apparatus  101   a  according to the first embodiment of the present invention. 
     As illustrated in  FIGS. 1 and 2 , the X-ray imaging apparatus  101   a  according to the first embodiment includes an X-ray generation unit  102 , a control unit  103 , a storing unit  104 , and an arm unit  105 . Further, the X-ray generation unit  102 , the control unit  103 , and the storing unit  104  are fixed to the arm unit  105 . 
     When the X-ray generation unit  102  receives an X-ray generation signal (described later) from an X-ray control unit  108  of the control unit  103 , which is to be described later, the X-ray generation unit  102  generates an X-ray to irradiate a subject H with the X-ray. The X-ray generation unit  102  includes an X-ray tube (not shown) for generating the X-ray, a high voltage generation unit (not shown) for driving the X-ray tube, and a collimator  107  for restricting an X-ray radiation area. 
     The X-ray tube generates the X-ray, for example, by irradiating an X-ray target made of tungsten or molybdenum with thermoelectrons emitted from a filament heated at high temperature. Further, the X-ray tube and the high voltage generation unit are disposed in the same container. The inside of the container is filled with insulating oil. 
     The collimator  107  is disposed in a radiation opening of the X-ray generation unit  102 . The collimator  107  restricts a radiation range of the X-ray radiated from the X-ray tube and is used for the purpose of reducing generation of scattering rays as much as possible. The collimator  107  is generally movable. Further, an operator can adjust the X-ray radiation range by moving a lead vane disposed on the collimator  107  while confirming the radiation range using a lamp disposed on the collimator  107 . In addition, the collimator  107  can also automatically adjust the X-ray radiation range (described later). 
     The storing unit  104  has a structure of enable storage (in other words, installation) of an X-ray reception unit  106 . When the radiography is performed, the X-ray reception unit  106  is stored (installed) in the storing unit  104 . 
     The X-ray reception unit  106  includes a reception surface R and is stored in the storing unit  104  so that the reception surface R faces toward the X-ray generation unit  102 . Then, the X-ray reception unit  106  receives, on the reception surface R, the X-ray radiated from the X-ray generation unit  102 . As the X-ray reception unit  106 , any known unit such as an FPD sensor, a CR cassette, or a film cassette can be used. 
     The FPD sensor or the like as the X-ray reception unit  106  has a size such as half size, a large quarter size, a quarter size, or the like. The half size has a short side size of 383.5±1.0 mm and a long side size of 459.5±1.0 mm. The large quarter size has a short side size of 307.5±1.0 mm and a long side size of 383.5±1.0 mm. The quarter size has a short side size of 281.5±1.0 mm and a long side size of  332 . 5 ± 1 . 0  mm. These sizes are defined by the JIS standard. There are two orientations of the FPD sensor or the like, including a portrait in which the FPD sensor or the like is longitudinal to the subject H and a landscape in which the FPD sensor or the like is transverse to the subject H. One of the orientations is appropriately selected in accordance with a part to be photographed and the purpose of the photography. 
     In the storing unit  104 , any of the FPD sensor, the CR cassette, and the film cassette as the X-ray reception unit  106  can be stored. Further, in the storing unit  104 , the size and the orientation of the X-ray reception unit  106  to be stored can are arbitrarily selected. In other words, in the storing unit  104 , the FPD sensor or the like in any size can be stored, and the orientation of the FPD sensor or the like to be stored (portrait or landscape) can be arbitrarily selected. 
     The storing unit  104  is made of a material having light weight and high rigidity such as any synthetic resin material or a carbon fiber reinforced plastic (CFRP). The storing unit  104  has a bag-like structure having an opening formed on one side. Further, the FPD sensor, the CR cassette, or the film cassette as the X-ray reception unit  106  can be inserted into and removed from the storing unit  104  through the opening. The height of the opening is larger than a thickness of 15 mm of the FPD sensor or the like. In addition, the side of the storing unit  104  on which the X-ray enters (the side on which the reception surface R of the X-ray reception unit  106  is disposed) is formed to have a uniform thickness so that the shadow thereof does not fall on the X-ray image. 
     When the storing unit  104  storing the X-ray reception unit  106  is inserted under the subject H who is lying, the X-ray generation unit  102  can radiate the X-ray toward the subject H. 
     Inside the storing unit  104 , an X-ray reception unit recognizing unit  112  is disposed. The X-ray reception unit recognizing unit  112  recognizes whether or not the X-ray reception unit  106  is stored in the storing unit  104  (installed or not). When the X-ray reception unit  106  is stored, the X-ray reception unit recognizing unit  112  recognizes a type (for example, which one of the FPD sensor, the CR cassette, and the film cassette is used), the size, and the orientation of the X-ray reception unit  106 . For instance, identification information is provided on the exterior of the X-ray reception unit  106 , and the X-ray reception unit recognizing unit  112  reads this identification information to perform the above-mentioned recognition. As the identification information provided on the exterior of the X-ray reception unit  106 , any known one-dimensional code, two-dimensional code, RFID tag, or the like can be used, for example. On the other hand, the X-ray reception unit recognizing unit  112  includes a predetermined reader of various types so as to read for the recognition the identification information provided on the exterior of the X-ray reception unit  106 . 
     Then, the X-ray reception unit recognizing unit  112  generates a recognition signal from a recognition result and sends the generated recognition signal to a radiation condition setting unit  109 . The recognition signal contains information regarding whether or not the X-ray reception unit  106  is stored, the type (which one of the FPD sensor, the CR cassette, and the film cassette is used), the size, and the installation orientation of the X-ray reception unit  106 . 
     Note that, when the X-ray reception unit  106  stored in the storing unit  104  is replaced after the X-ray generation unit  102  radiates the X-ray, the X-ray reception unit recognizing unit  112  performs recognition of the X-ray reception unit  106  again and updates the recognition signal. The X-ray reception unit recognizing unit  112  recognizes whether or not the X-ray reception unit  106  is replaced when the recognition signal is updated. When the X-ray reception unit  106  is recognized as the CR cassette or the film cassette (namely, a type that is used through replacement for each photography), and the recognition signal is not updated, the control unit  103  restricts the second X-ray radiation. In other words, when the recognition signal is not updated, the X-ray reception unit recognizing unit  112  determines that the X-ray reception unit  106  is not replaced, and restricts the second X-ray radiation. Thus, double X-ray radiation of the same CR cassette or film cassette can be prevented. 
     The control unit  103  includes the X-ray control unit  108 , the radiation condition setting unit  109 , an X-ray radiation instruction unit  110 , and a power supply unit  111 . 
     The radiation condition setting unit  109  can set the X-ray radiation condition based on operation by the operator. For instance, a touch panel is disposed on the exterior of the control unit  103 , and the operator uses this touch panel to perform the operation of setting the X-ray radiation condition. The X-ray radiation condition includes an X-ray tube voltage, an X-ray tube current, a radiation time, and the like. Note that, the radiation condition setting unit  109  can also set the X-ray radiation condition based on the recognition signal received from the X-ray reception unit recognizing unit  112 , and further, the radiation condition setting unit  109  can automatically set the X-ray radiation condition to a recommended value, or a predetermined value. Further, the radiation condition setting unit  109  calculates an X-ray radiation amount or the like based on the set X-ray radiation condition value to generate a radiation condition signal, and sends the generated radiation condition signal to the X-ray control unit  108 . The radiation condition signal contains information regarding the X-ray radiation condition such as the X-ray radiation amount. 
     An operation unit  119  is connected to (or disposed on) the X-ray radiation instruction unit  110 . The operation unit  119  includes a button or the like for operating the X-ray radiation instruction unit  110 . The X-ray radiation instruction unit  110  sends a signal for instructing the X-ray control unit  108  to radiate the X-ray (hereinafter referred to as an “X-ray radiation instruction signal”) based on the operation of the operation unit  119  by the operator. As the operation unit  119 , a deadman&#39;s X-ray radiation switch is used. In other words, when the X-ray radiation instruction unit  110  detects that the button disposed on the operation unit  119  is pressed by the operator, the X-ray radiation instruction unit  110  sends the X-ray radiation instruction signal to the X-ray control unit  108 . On the other hand, when the X-ray radiation instruction unit  110  detects that the button disposed on the operation unit  119  is released, the X-ray radiation instruction unit  110  promptly sends a signal for instructing the X-ray control unit  108  to stop the X-ray radiation (hereinafter referred to as an “X-ray radiation stop instruction signal”). 
     Note that, a remote control switch may be used for the X-ray radiation instruction unit  110  and the operation unit  119  so that the operator can perform remote operation. For instance, as the X-ray radiation instruction unit  110  and the operation unit  119 , it is possible to use a structure including an infrared reception unit disposed on the exterior of the control unit  103  and a remote switch for transmitting an infrared signal. In this structure, when the X-ray radiation instruction unit  110  detects that the operator has operated the button disposed on the operation unit  119 , the X-ray radiation instruction unit  110  sends the X-ray radiation instruction signal to the X-ray control unit  108 . On the other hand, when the X-ray radiation instruction unit  110  detects that the operator has released the button, the X-ray radiation instruction unit  110  promptly sends the X-ray radiation stop instruction signal to the X-ray control unit  108 . The X-ray radiation instruction unit  110  and the operation unit  119  may have a structure for communicating with the X-ray control unit  108  by a wireless method of the IEEE 802.11 standard, which is widespread as a wireless LAN for personal computers. 
     When the X-ray control unit  108  receives the radiation condition signal from the radiation condition setting unit  109  and receives the X-ray radiation instruction signal from the X-ray radiation instruction unit  110 , the X-ray control unit  108  generates the X-ray generation signal based on the received signals. Then, the X-ray control unit  108  sends the generated X-ray generation signal to the X-ray generation unit  102 . 
     The power supply unit  111  is a power supply for supplying power to each unit of the X-ray imaging apparatus  101   a , such as the X-ray generation unit  102 . Power supply from the outside to the power supply unit  111  may be commercial power supply of a single phase 100 V, or may be 12 V or 24 V DC power supply from a cigar lighter socket of a car. In addition, the power supply from the outside to the power supply unit  111  may be DC power supply from a battery such as a lithium ion battery, a nickel hydrogen battery, or a fuel cell. 
     Further, the power supply unit  111  boosts the voltage of the electric power supplied from the outside to approximately 300 V, for example. Then, the power supply unit  111  supplies the electric power with the boosted voltage to the high voltage generation unit disposed on the X-ray generation unit  102 . 
     The control unit  103  is a computer including a central processing unit (CPU), a RAM, a ROM, and the like. The central processing unit executes a computer program so as to cause the X-ray control unit  108 , the radiation condition setting unit  109 , the X-ray radiation instruction unit  110 , and the operation unit  119  to function. 
     The X-ray imaging apparatus  101   a  according to the first embodiment of the present invention has a fixed, invariable distance from the X-ray tube of the X-ray generation unit  102  to the reception surface R of the X-ray reception unit  106 . Therefore, the collimator  107  can drive the lead vane by a motor or the like based on the recognition signal received from the X-ray reception unit recognizing unit  112 , and automatically adjust the radiation range to be a predetermined range. The recognition signal contains information of whether or not the X-ray reception unit  106  is stored, the type (for example, which one of the FPD sensor, the CR cassette, and the film cassette is used), the size, and the installation orientation of the X-ray reception unit  106 . The recognition signal generated by the X-ray reception unit recognizing unit  112  is sent to the collimator  107  via the radiation condition setting unit  109  and the X-ray control unit  108  as described later. 
     Besides, the X-ray imaging apparatus  101   a  may have a structure further including a display unit (not shown) for displaying the X-ray image received by the FPD sensor when the FPD sensor is used as the X-ray reception unit  106 . As this display unit, various types of display apparatus such as a liquid crystal monitor can be used. 
     The arm unit  105  is a member for fixing the X-ray generation unit  102 , the control unit  103 , and the storing unit  104 . Note that, for convenience sake of description, the “upside” and “downside” of the arm unit  105  are set with reference to the state illustrated in  FIG. 1 , unless otherwise noted. 
     The arm unit  105  is formed of a rod-like member. The arm unit  105  includes a portion extending substantially horizontally on the downside (hereinafter referred to as a lower portion  151 ), a portion extending substantially horizontally on the upside (referred to as an upper portion  153 ), and a portion connecting the lower portion  151  and the upper portion  153  on the same side (referred to as an intermediate portion  152 ). Further, the lower portion  151 , the intermediate portion  152 , and the upper portion  153  are formed integrally. Therefore, the arm unit  105  has a substantially U-shape in side view. 
     The lower portion  151  and the upper portion  153  of the arm unit  105  are opposed to each other with a predetermined distance therebetween. Further, the subject H can be positioned in the space between the lower portion  151  and the upper portion  153  (for example, an area surrounded by the lower portion  151 , the intermediate portion  152 , and the upper portion  153 , which is hereinafter referred to as an inside). 
     The storing unit  104  is fixed to the lower portion  151  of the arm unit  105 . The control unit  103  is fixed to the intermediate portion  152  of the arm unit  105 . The X-ray generation unit  102  is fixed to the upper portion  153  of the arm unit  105 . In this way, the storing unit  104 , the control unit  103 , and the X-ray generation unit  102  are fixed to the arm unit  105 . Further, the arm unit  105  supports the X-ray generation unit  102  and the storing unit  104  in a cantilever manner. In other words, end portions of the lower portion  151  and the upper portion  153  on the same side (proximal end portions) are fixed ends connected to the intermediate portion  152 . The end portions on the opposite side (distal end portions) are free ends that are not fixed. According to this structure, when the radiography is performed, the X-ray radiated from the X-ray generation unit  102  irradiates the subject H without being blocked. 
     The X-ray generation unit  102  and the X-ray reception unit  106  are fixed to the arm unit  105  so that a positional relationship therebetween is fixed. Further, only the periphery of the bottom of the storing unit  104  is held in contact with the ground when the X-ray imaging apparatus  101   a  is installed in such a posture that the storing unit  104  is positioned on the downside as illustrated in  FIG. 1 . Therefore, even when the subject H lies on a bed or a futon (Japanese bedding), the X-ray imaging apparatus  101   a  can be used without adjusting the arm unit  105 . 
     The arm unit  105  is made of an aluminum alloy, titanium, a carbon fiber reinforced plastic (CFRP), or the like, for example. According to this structure, weight of the arm unit  105  can be reduced, and rigidity of the arm unit  105  can be enhanced. 
     Detailed structure of the arm unit  105  and a relationship among the X-ray generation unit  102 , the control unit  103 , the storing unit  104 , and the arm unit  105  are described with reference to  FIGS. 3 to 5 .  FIG. 3  schematically illustrates the relationship among the X-ray generation unit  102 , the control unit  103 , the storing unit  104 , and the arm unit  105 .  FIG. 4  is a schematic plan view of the X-ray imaging apparatus  101   a  in use as viewed from the above.  FIG. 5  schematically illustrates the X-ray imaging apparatus  101   a  in the state of being used in a sideways posture. 
     As illustrated in  FIG. 3 , the storing unit  104  storing the X-ray reception unit  106  and the X-ray generation unit  102  are fixed by the arm unit  105  so as to be opposed to each other with a predetermined distance therebetween. The X-ray reception unit  106  is stored in the storing unit  104  in such a posture that the reception surface R faces toward the X-ray generation unit  102 . A distance between a focal point F of the X-ray tube of the X-ray generation unit  102  and the reception surface R of the X-ray reception unit  106  stored in the storing unit  104  (distance C in  FIG. 3 ) is preferred to be 1,100 mm or less in view of portability. 
     A dashed dotted line L in  FIG. 3  is the normal passing through the center of the reception surface R of the X-ray reception unit  106 . As illustrated in  FIG. 3 , the X-ray generation unit  102  and the X-ray reception unit  106  are fixed so that the focal point F of the X-ray tube of the X-ray generation unit  102  is positioned above the center of the reception surface R of the X-ray reception unit  106  in the vertical direction (so as to be positioned on the normal L passing through the center of the reception surface R). With this structure, the X-ray radiated from the X-ray tube of the X-ray generation unit  102  passes through the subject H positioned between the upper portion  153  and the lower portion  151  of the arm unit  105  and is received by the X-ray reception unit  106  on the reception surface R. Therefore, a good X-ray image can be obtained. 
     The control unit  103  is fixed to the intermediate portion  152  of the arm unit  105  and is positioned between the X-ray generation unit  102  and the storing unit  104  in the vertical direction. Further, a center of gravity G 2  of the control unit  103  in the vertical direction is positioned lower (closer to the storing unit  104 ) than a center of gravity G 1  of the arm unit  105  to which the X-ray generation unit  102  and the storing unit  104  storing the X-ray reception unit  106  are fixed. Therefore, in a state where the X-ray imaging apparatus  101   a  is installed on a substantially horizontal surface with the lower portion  151  being on the downside, the center of gravity G 2  of the control unit  103  is positioned lower than the center of gravity G 1  of the arm unit  105  to which the X-ray generation unit  102  and the storing unit  104  storing the X-ray reception unit  106  are fixed. With this structure, in a state where the X-ray imaging apparatus  101   a  is installed in such a posture that the storing unit  104  is positioned on the downside, a position of the center of gravity of the X-ray imaging apparatus  101   a  can be low. Therefore, even when the X-ray imaging apparatus  101   a  is placed on an examination table, the posture of the X-ray imaging apparatus  101   a  can be stabilized enough to prevent falling. 
     The arm unit  105  further has a function of protecting each of the X-ray generation unit  102 , the control unit  103 , and the storing unit  104  from an impact applied from the outside (for example, from the side opposite to the space in which the subject H is positioned, and the same is true in the following description). 
     For instance, as illustrated in  FIG. 3 , in side view, the X-ray generation unit  102 , the control unit  103 , and the storing unit  104  are disposed so that the outer circumference surfaces thereof are positioned inside the outer circumference surface of the arm unit  105 . In other words, the outer circumference surfaces of the X-ray generation unit  102 , the control unit  103 , and the storing unit  104  do not protrude from the outer circumference surface of the arm unit  105  in side view. With this structure, it is possible to prevent an impact from being applied from the outside of the X-ray imaging apparatus  101   a  to the X-ray generation unit  102 , the control unit  103 , and the storing unit  104 , when the X-ray imaging apparatus  101   a  is touched by a human or an object. In addition, a structure may be adopted, in which a protective member  155  (for example, an external cover member) for protecting the X-ray generation unit  102 , the control unit  103 , and the storing unit  104  is disposed on the arm unit  105 . For instance, a structure can be adopted, in which a rod-like or grid-like member such as a rib or a plate-like member is disposed as the protective member  155  on the outer side of the X-ray generation unit  102 , the control unit  103 , and the storing unit  104 . Even with this structure, it is possible to prevent an impact from being applied from the outside of the X-ray imaging apparatus  101   a  to the X-ray generation unit  102 , the control unit  103 , and the storing unit  104  when the X-ray imaging apparatus  101   a  is touched or struck by a human or an object. Therefore, the X-ray generation unit  102 , the control unit  103 , and the storing unit  104  can be protected. 
     The distal end portion of the lower portion  151  of the arm unit  105  (end portion on the opposite side to the intermediate portion  152 ) is formed into a tapered shape. For instance, the distal end portion of the lower portion  151  of the arm unit  105  is formed into a triangular shape as illustrated in  FIG. 3  or into a circular or elliptic shape. According to the structure in which the distal end portion of the lower portion  151  of the arm unit  105  is formed into a tapered shape, the lower portion  151  of the arm unit  105  can be easily inserted under the subject H. 
     In addition, as illustrated in  FIG. 4 , a handle  156  to be used for the operator to grip is disposed close to a part of the upper portion  153  of the arm unit  105 , in which the X-ray generation unit  102  is disposed. Specifically, as illustrated in  FIG. 4 , the upper portion  153  of the arm unit  105  has two rod-like members extending substantially horizontally in parallel to each other. Further, the rod-like handle  156  is further disposed to connect the distal end portions of the two rod-like members. 
     Further, as illustrated in  FIG. 5 , this handle  156  is formed into such a shape that the posture of the X-ray imaging apparatus  101   a  is stabilized even when the X-ray imaging apparatus  101   a  is installed sideways. 
       FIG. 5  schematically illustrates a state where the X-ray imaging apparatus  101   a  is installed in the sideways posture. In the sideways posture, the distal end portion of the upper portion  153  or the handle  156  and the distal end portion of the lower portion  151  of the arm unit  105  are held in contact with the ground. In the state illustrated in  FIG. 5 , the shape and dimensions of the handle  156  are determined so that a center of gravity G o  of the X-ray imaging apparatus  101   a  is positioned between the distal end portion of the upper portion  153  or the handle  156  (a part held in contact with the ground) and the distal end portion of the lower portion  151  (a part held in contact with the ground) of the arm unit  105 . For instance, as illustrated in  FIG. 3 , a straight line M, which passes through the distal end portion of the lower portion  151  and the distal end portion of any one of the upper portion  153  and the handle  156 , which has a longer distance from the intermediate portion  152 , is set to be perpendicular to the extending direction of the upper portion  153  and the lower portion  151 . According to this structure, as illustrated in  FIG. 5 , the upper portion  153  and the lower portion  151  are substantially perpendicular to the ground surface (for example, the horizontal surface). Further, the X-ray generation unit  102  is fixed to the upper portion  153 , the storing unit  104  is fixed to the lower portion  151 , and the control unit  103  is fixed to the intermediate portion  152 . Therefore, as illustrated in  FIG. 5 , the center of gravity G 0  of the X-ray imaging apparatus  101   a  is positioned between the distal end portion of the upper portion  153  or the handle  156  (a part held in contact with the ground) and the distal end portion of the lower portion  151  (a part held in contact with the ground) of the arm unit  105 . Therefore, even in the state where the X-ray imaging apparatus  101   a  is installed in the sideways posture and the distal end portion of the upper portion  153  or the handle  156  and the distal end portion of the lower portion  151  are held in contact with the ground, the posture of the X-ray imaging apparatus  101   a  does not become unstable. 
     A gap is formed between the arm unit  105  and the X-ray generation unit  102  as illustrated in  FIG. 4 . In the same manner, a gap (not shown) is also formed between the arm unit  105  and the control unit  103 . Therefore, the operator can grip the arm unit  105  by inserting a hand in this gap. In addition, through these gaps, the operator can confirm the position or the posture of the subject H from the outside of the X-ray imaging apparatus  101   a.    
     Next, an example of a process of the X-ray imaging apparatus  101   a  according to the first embodiment is described with reference to  FIG. 6 .  FIG. 6  is a flowchart illustrating the example of the process of the X-ray imaging apparatus  101   a  according to the first embodiment. This process is stored as a computer program (computer software) in the RAM or the ROM of the computer of the control unit  103  except for the process and operation performed by the operator. Then, the central processing unit of the computer of the control unit  103  reads and executes the computer program so that this process is performed. 
     First, in the first Step S 101 , the X-ray reception unit  106  is stored in the storing unit  104  by the operator. In Step S 102 , the X-ray reception unit recognizing unit  112  recognizes whether or not the X-ray reception unit  106  is stored, and further recognizes the type, the size, and the orientation of the X-ray reception unit  106  to generate the recognition signal. Then, the X-ray reception unit recognizing unit  112  sends the generated recognition signal to the radiation condition setting unit  109 . 
     In Step S 103 , the collimator  107  receives the recognition signal generated by the X-ray reception unit recognizing unit  112  via the radiation condition setting unit  109  and the X-ray control unit  108 . Then, the collimator  107  automatically adjusts the X-ray radiation range based on the received recognition signal. If the FPD sensor is used for the X-ray reception unit  106 , Steps S 102  and  5103  can be omitted by storing the FPD sensor in the storing unit  104  in advance. 
     In Step S 104 , the storing unit  104  of the X-ray imaging apparatus  101   a  (lower portion  151  of the arm unit  105 ) is inserted under the lying subject H by the operator. 
     Note that, Step S 104  may be performed before Step S 101 . In other words, a structure may be adopted, in which the storing unit  104  of the X-ray reception unit  106  is inserted after the X-ray imaging apparatus  101   a  is inserted under the subject H. 
     In Step S 105 , the radiation condition setting unit  109  sets the X-ray radiation condition including the X-ray tube voltage, the X-ray tube current, the radiation time, and the like based on operation by the operator using the touch panel or the like disposed on the exterior of the control unit  103 . The radiation condition setting unit  109  may set the X-ray radiation condition based on the recognition signal containing information such as the type, the size, and the orientation of the X-ray reception unit  106 , which is received from the X-ray reception unit recognizing unit  112  in Step S 102 . Further, the radiation condition setting unit  109  may also automatically set the X-ray radiation condition to a recommended value or a predetermined value. 
     In Step S 106 , the X-ray radiation instruction unit  110  sends the X-ray radiation instruction signal to the X-ray control unit  108  when the deadman&#39;s button is pressed by the operator. The X-ray control unit  108  receives the radiation condition signal from the radiation condition setting unit  109  and receives the X-ray radiation instruction signal from the X-ray radiation instruction unit  110 . Then, the X-ray control unit  108  sends the X-ray generation signal to the X-ray generation unit  102  at a timing when the X-ray radiation condition is satisfied. When the X-ray generation unit  102  receives the X-ray generation signal, the X-ray generation unit  102  radiates the X-ray. 
     In Step S 107 , after the X-ray generation unit  102  radiates the X-ray, the X-ray imaging apparatus  101 a displays the photographed image on the display unit (not shown). Thus, the operator can confirm the photographed X-ray image. The method of confirming the photographed X-ray image is different depending on the type of the X-ray reception unit  106  or the like. 
     As described above, the first embodiment of the present invention provides the structure in which the operator stores the X-ray reception unit  106  in the storing unit  104  in advance in Step S 101 , and the radiation condition setting unit  109  sets the radiation condition in Step S 105 . With this structure, the operator can operate the X-ray imaging apparatus  101   a  to radiate the X-ray only by inserting the storing unit  104  of the X-ray imaging apparatus  101   a  under the subject H in Step S 104  and operating the X-ray radiation instruction unit  110  in Step S 106 . Further, it is possible to prevent unnecessary radiation or double radiation when the CR cassette or the film cassette is used as the X-ray reception unit  106 . Therefore, operability can be improved. 
     Second Embodiment  
     Next, an X-ray imaging apparatus  101   b  according to a second embodiment of the present invention is described with reference to  FIG. 7 . Note that, the same reference numerals or symbols are assigned to the same components as those in the first embodiment, and hence redundant description is omitted.  FIG. 7  is a block diagram schematically illustrating a system configuration of the X-ray imaging apparatus  101   b  according to the second embodiment. The X-ray imaging apparatus  101   b  according to the second embodiment includes an FPD sensor as the X-ray reception unit  106 , and is connected to an HIS/RIS server (not shown) or a PACS server (not shown) so as to transmit/receive signals from/to the server(s). 
     As illustrated in  FIG. 7 , the X-ray imaging apparatus  101   b  according to the second embodiment includes the X-ray generation unit  102 , the control unit  103 , the storing unit  104 , a sensor control unit  113 , and a sensor information display unit  114 . Further, the X-ray imaging apparatus  101   b  is connected to the HIS/RIS server or the PACS server (not shown) via a network  115  so as to transmit/receive signals from/to the server(s). 
     The sensor control unit  113  controls the X-ray reception unit  106 . The sensor information display unit  114  controls the X-ray control unit  108  and the sensor control unit  113 , and also controls a photography sequence of the X-ray imaging apparatus  101   b . Further, the sensor information display unit  114  performs display so that the operator can perform setting concerning the radiography. Note that, some operation to perform setting concerning the radiography may be omitted by using information on the subject H, which is transmitted from the HIS/RIS server. 
     Further, the sensor information display unit  114  displays information on the subject H (patient) (for example, a name, a sex, an age of the patient, a part to be photographed, and the like), and an electronic image, a histogram of the X-ray dose, and the like, which are sent from the FPD sensor as the X-ray reception unit  106 . Note that, the sensor control unit  113  and the sensor information display unit  114  are constituted separately from a main body of the X-ray imaging apparatus  101   b . In addition, the sensor control unit  113  and the sensor information display unit  114  are constituted integrally, for example. For instance, as the sensor control unit  113  and the sensor information display unit  114 , a portable tablet PC which has a plate-like outer shape and includes a touch-panel display and input unit or a portable laptop PC is used. 
     As communication between the sensor control unit  113  and the X-ray reception unit  106 , it is possible to use the wireless communication of the IEEE 802.11 standard, which is used as a wireless LAN for personal computers. In the same manner, as communication between the sensor information display unit  114  and at least one of the X-ray control unit  108 , the sensor control unit  113 , and the network  115 , it is also possible to use the wireless communication of the IEEE 802.11 standard. 
     Next, an example of a process of the X-ray imaging apparatus  101   b  according to the second embodiment of the present invention is described with reference to  FIG. 8 .  FIG. 8  is a flowchart illustrating the example of the process of the X-ray imaging apparatus  101   b  according to the second embodiment of the present invention. 
     In the first Step S 201 , in the same manner as Step S 101  of the first embodiment (see  FIG. 6 ), the X-ray reception unit  106  is stored in the storing unit  104  by the operator. In the second embodiment, the FPD sensor is used for the X-ray reception unit  106 . 
     In Step S 202 , the X-ray reception unit recognizing unit  112  recognizes whether or not the X-ray reception unit  106  is stored, and further recognizes the type, the size, the orientation of the X-ray reception unit  106 , and the like to generate the recognition signal. Then, the X-ray reception unit recognizing unit  112  sends the generated recognition signal to the radiation condition setting unit  109 . The recognition signal is sent from the X-ray reception unit recognizing unit  112  to the collimator  107  via the radiation condition setting unit  109  and the X-ray control unit  108 . 
     In Step S 203 , in the same manner as Step S 103  of the first embodiment (see  FIG. 6 ), the collimator  107  receives the recognition signal from the X-ray reception unit recognizing unit  112 , and automatically adjusts the X-ray radiation range based on the received recognition signal. Note that, Steps S 202  and S 203  can be omitted by storing the FPD sensor as the X-ray reception unit  106  in the storing unit  104  in advance. 
     In Step S 204 , in the same manner as Step S 104  of the first embodiment (see  FIG. 6 ), the storing unit  104  of the X-ray imaging apparatus  101   b  is inserted under the lying subject H by the operator. 
     Note that, Step S 204  may be performed before Step S 201 . In other words, a structure may be adopted, in which the X-ray reception unit  106  is stored in the storing unit  104  after the storing unit  104  of the X-ray imaging apparatus  101   b  is inserted under the subject H. 
     In Step S 205 , in the same manner as Step S 105  of the first embodiment (see  FIG. 6 ), the radiation condition setting unit  109  sets the X-ray radiation condition including the X-ray tube voltage, the X-ray tube current, the radiation time, and the like. The radiation condition setting unit  109  determines a set value based on the operation by the operator using the touch panel or the like disposed on the exterior of the control unit  103 . Note that, the radiation condition setting unit  109  may set the X-ray radiation condition based on the recognition signal containing information such as the type, the size, and the orientation of the X-ray reception unit  106 , which is received from the X-ray reception unit recognizing unit  112  in Step S 202 . Further, the radiation condition setting unit  109  may also automatically set the X-ray radiation condition to a recommended value or a predetermined value. Besides, the radiation condition setting unit  109  may set the X-ray radiation condition based on an input from the sensor information display unit  114 . Note that, the radiation condition setting unit  109  can omit a part of the input from the sensor information display unit  114  by using the patient information transmitted from the HIS/RIS server. For instance, it is possible to omit an input of the X-ray radiation condition including the X-ray tube voltage, the X-ray tube current, the radiation time, and the like. 
     In Step S 206 , in the same manner as Step S 106  of the first embodiment (see  FIG. 6 ), the X-ray radiation instruction unit  110  sends the X-ray radiation instruction signal to the X-ray control unit  108  when the deadman&#39;s button is pressed by the operator. The X-ray control unit  108  receives the radiation condition signal from the radiation condition setting unit  109  and receives the X-ray radiation instruction signal from the X-ray radiation instruction unit  110 . Then, the X-ray control unit  108  sends the X-ray generation signal to the X-ray generation unit  102  at the timing when the X-ray radiation condition is satisfied. When the X-ray generation unit  102  receives the X-ray generation signal, the X-ray generation unit  102  radiates the X-ray. 
     In Step S 207 , the X-ray reception unit  106  performs A/D conversion of a charge corresponding to the X-ray dose after passing through the subject H to generate the electronic image, and sends the electronic image to the sensor information display unit  114 . The sensor information display unit  114  displays the electronic image together with the patient information, the histogram of the X-ray dose, and the like. 
     The sensor information display unit  114  performs predetermined image processing on the electronic image in accordance with the operation by the operator. Further, the sensor information display unit  114  performs the process of storing the electronic image in the PACS server. 
     Note that, when it is desired to repeat the process of the X-ray imaging apparatus  101   b  along with the changes of the subject H, a part to be photographed, or the like, the process can be performed from Step S 204 . 
     As described above, the second embodiment provides the structure in which the FPD sensor as the X-ray reception unit  106  is stored in the storing unit  104 , and the information such as the patient information is effectively used from the HIS/RIS server via the network  115 . Thus, the operator can omit setting of the X-ray radiation condition including the X-ray tube voltage, the X-ray tube current, and the radiation time. Further, the X-ray imaging apparatus  101   b  uses the information such as the patient information transmitted from the HIS/RIS server. Therefore, the operator can omit input or setting of the patient information. In addition, because the FPD sensor is used as the X-ray reception unit  106 , when repeating the process in the X-ray imaging apparatus  101   b  along with the changes of the subject H, the part to be photographed, or the like, it is possible to perform the process from Step S 204 . In this way, compared with the first embodiment, the operability can be further improved. 
     Third Embodiment  
     Next, an X-ray imaging apparatus  101   c  according to a third embodiment of the present invention is described with reference to  FIG. 9 .  FIG. 9  is a block diagram schematically illustrating a structure of a main part of the X-ray imaging apparatus  101   c  according to the third embodiment of the present invention. Note that, the same reference numerals or symbols are assigned to the same components as those in the first embodiment and the second embodiment, and hence redundant description is omitted. 
     As illustrated in  FIG. 9 , the X-ray imaging apparatus  101   c  according to the third embodiment is different from the X-ray imaging apparatus  101   b  according to the second embodiment in that the sensor control unit  113  is disposed in the control unit  103 . Except for this, the structure is the same as that of the X-ray imaging apparatus  101   b  according to the second embodiment. 
     The sensor control unit  113  is disposed in the control unit  103  and is controlled by the control unit  103 . With this structure, the sensor information display unit  114  is not required to control the sensor control unit  113 . Therefore, the sensor information display unit  114  is not required to have high processing performance. Therefore, as the sensor information display unit  114 , for example, a personal mobile phone having a general-purpose OS installed therein can be used. 
     Fourth Embodiment  
     Next, an X-ray imaging apparatus  101   d  according to a fourth embodiment of the present invention is described with reference to  FIG. 10 .  FIG. 10  is a block diagram schematically illustrating a system configuration of the X-ray imaging apparatus  101   d  according to the fourth embodiment. Note that, the same reference numerals or symbols are assigned to the same components as those in the first embodiment to the third embodiment, and hence redundant description is omitted. 
     As illustrated in  FIG. 10 , the X-ray imaging apparatus  101   d  according to the fourth embodiment of the present invention is different from the X-ray imaging apparatus  101   c  according to the third embodiment in that the sensor control unit  113  is disposed in the X-ray reception unit  106 . Except for this, the same structure as that in the third embodiment can be used. If the sensor control unit  113  is disposed in the X-ray reception unit  106 , all the FPD sensor, the CR cassette, and the film cassette can be stored in the storing unit  104  without disposing an independent sensor control unit  113 . Further, with this structure, operability can be improved as in the third embodiment. 
     As described above, according to each embodiment of the present invention, the X-ray tube, the storing unit for storing the X-ray reception unit, and the control unit for controlling the X-ray tube are fixed to the same arm unit, and hence portability of the X-ray imaging apparatus can be improved. In addition, according to each embodiment of the present invention, it is not necessary to adjust the radiation field position by the X-ray source and to set the radiation condition. Therefore, easiness of installation and operability can be improved. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2012-045678, filed Mar. 1, 2012, which is hereby incorporated by reference herein in its entirety.