Patent Publication Number: US-2018035524-A1

Title: Radiation irradiation device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2016-145895, filed on Jul. 26, 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 radiation irradiation device having a radiation source that receives electric power supply from a battery. 
     2. Description of the Related Art 
     In the related art, portable radiation irradiation devices used in a case where a patient&#39;s radiation image are captured in operating rooms, examination rooms, or inpatient rooms have been suggested variously. 
     The portable radiation irradiation devices basically include a leg part enabled to travel by wheels, a main body part that houses a control part consisting of a battery for driving a radiation source, an electric circuit related to the driving of the radiation source, and the like and is held on the leg part, and an arm part connected to the main body part, and are configured by attaching the radiation source to a tip of the arm part. 
     When such radiation irradiation devices are used, a radiation irradiation device is first moved to the vicinity of a patient&#39;s bed. Next, the radiation source is moved to a desired position, and a radiation detector is moved to a desired position behind a subject. Then, in this state, the subject is irradiated with radiation by driving the radiation source, and a radiation image of the subject is acquired by detecting the radiation transmitted through the subject using the radiation detector. 
     Here, in the related art, in the portable radiation irradiation devices, lead storage batteries are used as batteries. However, in a case where the lead storage batteries are frequently charged, degradation of the batteries becomes early due to a memory effect, and energy density is small. Therefore, there are problems in that the weight becomes heavy. 
     Thus, it is suggested that lithium ion batteries are used as the batteries of the radiation irradiation devices (for example, refer to JP2013-180059A, JP2010-273827A, and JP2014-150948A). 
     SUMMARY OF THE INVENTION 
     However, even in a case where the lithium ion batteries are used, there are several problems. The lithium ion batteries have large internal resistance because the lithium ion batteries are connected in series. Hence, in a case where a high current is sent through a radiation source when generating radiation, a voltage drop of the lithium ion batteries becomes large, and becomes equal to or lower than a lower limit of battery rating. As a result, the lifespan of the lithium ion batteries becomes short. 
     Additionally, if the number of lithium ion batteries is increased by connecting the lithium ion batteries more in series, the value of a current of each lithium ion battery can be held down. However, due to the serialization, internal resistance becomes large, and the voltage drop increases. 
     The invention is to provide a radiation irradiation device that can prevent degradation of a battery resulting from a high current that flows when radiation is generated, in view of the above problems. 
     A radiation irradiation device of the invention includes a radiation generating part that generates radiation; a battery part that supplies electric power to the radiation generating part; and an emission instruction receiving part that receives an emission instruction of the radiation from the radiation generating part. The battery part has a storage battery, a capacitor connected in parallel to the storage battery, a switching part that performs switching from a state where electric power is supplied from the storage battery to the capacitor to a state where electric power is supplied from the capacitor to the radiation generating part. The switching part switches between the states of the electric power supply according to an instruction received at the emission instruction receiving part. 
     Additionally, in the radiation irradiation device of the above invention, the switching part can have a switch element connected between the storage battery and the capacitor. 
     Additionally, in the radiation irradiation device of the above invention, the emission instruction receiving part can receive two-step instructions of an emission preparation instruction of the radiation and an emission instruction of the radiation, and the switching part can be brought into a state where electric power is supplied from the storage battery to the capacitor, according to the emission preparation instruction of the radiation. 
     Additionally, the radiation irradiation device of the above invention can further include a notification part that performs notification of charging from the storage battery to the capacitor being completed. 
     Additionally, in the radiation irradiation device of the above invention, the notification part can include a light-emitting part that emits light when the charging from the storage battery to the capacitor is completed. 
     Additionally, the radiation irradiation device of the above invention can further include a reverse current suppressing part that suppresses a reverse current from the capacitor to the storage battery. 
     Additionally, in the radiation irradiation device of the above invention, the reverse current suppressing part can have a diode element. 
     Additionally, the radiation irradiation device of the above invention can further include an inrush current suppressing part that suppresses an inrush current from the storage battery to the capacitor. 
     Additionally, in the radiation irradiation device of the above invention, the inrush current suppressing part can have a resistance element. 
     Additionally, in the radiation irradiation device of the above invention, an electric double layer capacitor can be used as the capacitor. 
     Additionally, in the radiation irradiation device of the above invention, a lithium ion battery can be used as the storage battery. 
     According to the radiation irradiation device of the invention, the battery part has the storage battery, the capacitor connected in parallel to the storage battery, the switching part that performs the switching from the state where electric power is supplied from the storage battery to the capacitor to the state where electric power is supplied from the capacitor to the radiation generating part. The switching part switches between the states of the electric power supply according to the instruction received at the emission instruction receiving part. Hence, since electric power is not directly supplied from the storage battery to the radiation generating part but electric power is supplied to the radiation generating part with the discharge voltage of the capacitor when radiation is generated from the radiation generating part, degradation resulting from a voltage drop of the storage battery can be prevented. 
     Additionally, since the states of the electric power supply are switched therebetween according to the instruction received at the emission instruction receiving part, the discharge voltage of the capacitor can be supplied to the radiation generating part at a user&#39;s desired timing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating an entire shape of a radiation irradiation device of an embodiment of the invention. 
         FIG. 2  is a view illustrating the state when the radiation irradiation device of the embodiment of the invention is used. 
         FIG. 3  is a view of a leg part as seen from below. 
         FIG. 4  is a schematic view illustrating an electrical configuration of a battery part and a radiation generating part. 
         FIG. 5  is a timing chart for explaining the operation from charging to a capacitor of the battery part to exposure of radiation. 
         FIG. 6  is a view illustrating another embodiment of the battery part. 
         FIG. 7  is a view illustrating an example of a gate voltage applied to a switch element. 
         FIG. 8  is a view illustrating still another embodiment of the battery part. 
         FIG. 9  is a view of the radiation irradiation device illustrated in  FIG. 1  as seen from the front. 
         FIG. 10  is an external perspective view of a radiation detector as seen from a radiation detection surface side. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, a radiation irradiation device of an embodiment of the invention will be described in detail, referring to the drawings. Although the invention has features in the configuration of electric power supply to the radiation generating part in the radiation irradiation device, the entire configuration of the radiation irradiation device will first be described.  FIG. 1  is a perspective view illustrating the entire shape of the radiation irradiation device of the present embodiment when being not used, and  FIG. 2  is a side view illustrating the state when the radiation irradiation device of the present embodiment is used. In addition, in the following, an upper side and a lower side in the vertical direction in a state where the radiation irradiation device is placed on, for example, a device placement surface, such as a floor of a medical institution, are referred to as “up” and “down”, respectively, and a direction perpendicular to the vertical direction in the same state is referred to as a “horizontal” direction. Additionally, in the views to be described below, the vertical direction is defined as a z direction, a leftward-rightward direction of the radiation irradiation device is defined as an x direction, and a forward-backward direction of the radiation irradiation device is defined as a y direction. In addition, the front herein means a side to which an arm part extends from a main body part of the radiation irradiation device when the device is used. 
     As illustrated in  FIGS. 1 and 2 , a radiation irradiation device  1  of the present embodiment includes a leg part  10 , a main body part  20 , a supporting member  30 , an arm part  40 , and a radiation generating part  50 . 
     The leg part  10  is capable of traveling on a device placement surface  2 , and consists of a plate-shaped pedestal part  11  on which the main body part  20  is placed, and a foot arm part  12  that extends from the pedestal part  11  toward the front.  FIG. 3  is a view of the leg part  10  as seen from below. As illustrated in  FIG. 3 , the foot arm part  12  is formed in a V shape that widens in the leftward-rightward direction toward the front. First casters  10   a  are respectively provided on bottom surfaces of two tip parts  12   a  at the front of the foot arm part  12 , and second casters  10   b  are respectively provided on bottom surfaces of two corners at the rear of the pedestal part  11 . By forming the foot arm part  12  in a V shape as described above, for example, as compared to a case where the entire leg part  10  is formed in a rectangular shape, an edge part of the leg part does not easily collide against its surrounding obstacle when the leg part  10  is rotated. Thus, handling can be made easy. Additionally, weight reduction can also be achieved. 
     Each first caster  10   a  has a shaft that extends in the upward-downward direction, and is attached to the foot arm part  12  such that a rotating shaft of a wheel is revolvable within a horizontal plane about the shaft of the first caster. Additionally, each second caster  10   b  also has a shaft that extends in the upward-downward direction, and is attached to the pedestal part  11  such that a rotating shaft of a wheel is revolvable within the horizontal plane about the shaft of the second caster. In addition, the rotating shaft of each wheel herein is a rotating shaft when the wheel rotates and travels. The leg part  10  is configured so as to be capable of traveling in an arbitrary direction on the device placement surface  2  by the first casters  10   a  and the second casters  10   b.    
     Additionally, as illustrated in  FIG. 1 , a pedal part  13  is provided at the rear of the leg part  10 . The pedal part  13  consists of two pedals of a first pedal  13   a  and a second pedal  13   b . The first pedal  13   a  is a pedal for bringing the second casters  10   b  into a non-revolvable state. As a user steps on the first pedal  13   a , the second casters  10   b  are configured so as to be locked in revolution by a locking mechanism and brought into the non-revolvable state. 
     Additionally, the second pedal  13   b  is a pedal for bringing the second casters  10   b  into a revolvable state from the non-revolvable state. As the user steps on the second pedal  13   b , the second casters  10   b  are configured so as to be released from the locking by the locking mechanism and brought into the revolvable state again. 
     A well-known configuration can be used as the locking mechanism that locks the revolution of the second casters  10   b . For example, the revolution may be locked such that both sides of the wheels of the second casters  10   b  are sandwiched by plate-shaped members, or the revolution may be locked by providing members that stop the rotation of shafts of the second caster  10   b  that extend in the upward-downward direction. 
     The main body part  20  is placed on the pedestal part  11  of the leg part  10 , and includes a housing  21 . A control part  22  that controls driving of the radiation irradiation device  1  and an electric power supply part  60  are housed within the housing  21 . 
     The control part  22  performs control regarding generation and irradiation of radiation, such as a tube current, irradiation time, and a tube voltage, in the radiation generating part  50 , and control regarding acquisition of radiation images, such as image processing of a radiation image acquired by the radiation detector to be described below. The control part  22  is configured of, for example, a computer in which a program for control is installed, exclusive hardware, or combination of both. 
     The electric power supply part  60  supplies electric power to the radiation generating part  50 , a monitor  23 , and the radiation detector housed within, a cradle  25  to be described below. In addition, the monitor  23  may be configured so as to be attachable to and detachable from the main body part  20 . In that case, the electric power supply part  60  supplies electric power to a battery built in the monitor  23  to charge the battery. Additionally, the radiation detector also has a battery built therein, and the electric power supply part  60  supplies electric power to the built-in battery to charge the battery. 
       FIG. 4  is a schematic view illustrating an electrical configuration of the electric power supply part  60  and the radiation generating part  50 . As illustrated in  FIG. 4 , the electric power supply part  60  includes a battery part  61 , an inverter circuit part  62 , and a first booster circuit part  63 . 
     The battery part  61  includes a lithium ion battery  61   a , a capacitor  61   b , a switch element  61   c , and a battery control part  64 . 
     The lithium ion battery  61   a  is equivalent to a storage battery of the invention and is a cell obtained by connecting a plurality of lithium ion batteries in parallel. The lithium ion battery  61   a  of the present embodiment outputs a voltage of 48 V. Although the voltage output from the lithium ion battery  61   a  is not limited to 48 V, it is desirable that this voltage is 60 V or less. By setting the voltage to 60 V or less, the insulation creepage space distance can be made small, and size reduction can be achieved. 
     Additionally, although one lithium ion battery is used in the present embodiment, the invention is not limited to this. Two or more lithium ion batteries may be connected in parallel and used. In this case, in the plurality of lithium ion batteries, it is preferable to short-circuit the same poles. Noise can be reduced by connecting the lithium ion batteries in this way. 
     Additionally, by connecting the lithium ion batteries in parallel in this way, as compared to a case where lithium ion batteries are connected in series, the insulation creepage space distance can be made small, and size reduction can be achieved. However, two or more lithium ion batteries may be connected in series. 
     Additionally, in the present embodiment, the lithium ion battery is used as the storage battery from a viewpoint of weight reduction and easy handling. However, the invention is not limited to this. A battery consisting of a nickel hydride battery, a battery consisting of a NaS battery, a battery consisting of a fuel cell, and the like can be used. In addition, the storage battery may not be necessarily installed within a main body part  20 . For example, storage batteries of electric automobiles may be used. 
     The capacitor  61   b  is connected in parallel to the lithium ion battery  61   a , and is charged by the lithium ion battery  61   a . Although it is preferable to use an electric double layer capacitor as the capacitor  61   b , the invention is not limited to this, and an electrolytic capacitor may be used. As the capacity of the capacitor  61   b , it is desirable to set the capacity such that the voltage output from the electric power supply part  60  becomes 4 times or more and 6 times or less the output voltage of the lithium ion battery  61   a.    
     By setting the voltage output from the electric power supply part  60  to 4 times or more the output voltage of the lithium ion battery  61   a , a resistance against the noise from the outside when going via the cable part  70  to be described below can be made stronger. Additionally, by setting the voltage output from the electric power supply part  60  to 6 times or less the output voltage of the lithium ion battery  61   a , it is not necessary to use a high-voltage cable as the cable part  70 , and reduction of cost can be achieved. Moreover, since wiring line coating of the cable part  70  can be made thin, the degree of freedom of the cable part  70  can be improved. Accordingly, the movement of the arm part  40  (to be described below) in which the cable part  70  extends is can be made smooth. Specifically, it is desirable that the voltage output from the electric power supply part  60  is 60 V or more and 300 V or less. In the present embodiment, the voltage output from the electric power supply part  60  is set to 250 V. 
     The switch element  61   c  is connected between the lithium ion battery  61   a  and the capacitor  61   b , and is turned on and off according to the operation of an exposure switch  90  to be described below. As the switch element  61   c , for example, it is preferable to use a semiconductor switch, such as an FET (field effect transistor) switch. However, the invention is not limited to this, and a mechanical switch, such as a relay, may be used. 
     The capacitor  61   b  is charged by the lithium ion battery  61   a  while the switch element  61   c  is turned on and when the switch element  61   c  is turned off, the voltage charged by the capacitor  61   b  is discharged. 
     The battery control part  64  controls ON and OFF states of the switch element  61   c  according to the operation of the exposure switch  90 . Specifically, in the present embodiment, an FET switch is used as the switch element  61   c , and the battery control part  64  applies a gate voltage to a gate of the FET switch according to the operation of the exposure switch  90 . In addition, in the present embodiment, the switch element  61   c  and the battery control part  64  are equivalent to a switching part of the invention. 
     The inverter circuit part  62  converts a direct current voltage discharged from the capacitor  61   b  of the battery part  61  into an alternating voltage. Specifically, the inverter circuit part  62  includes a positive electrode side inverter circuit  62   a  and a negative electrode side inverter circuit  62   b . In addition, the circuit configuration of the inverter circuits is not limited to the circuit configuration illustrated in  FIG. 4 , and other well-known inverter circuits may be adopted. 
     The first booster circuit part  63  boosts an alternating voltage output from the inverter circuit part  62 . Specifically, the first booster circuit part  63  includes a positive electrode side first booster circuit  63   a  and the negative electrode side first booster circuit  63   b . The positive electrode side first booster circuit  63   a  of the present embodiment boosts an alternating voltage output from the positive electrode side inverter circuit  62   a , and boosts the alternating voltage to, for example, an alternating voltage of 4 times or more and 6 times or less. In the present embodiment, the positive electrode side first booster circuit  63   a  boosts an alternating voltage of 48 V output from the positive electrode side inverter circuit  62   a  to an alternating voltage of 250 V. 
     Meanwhile, the negative electrode side first booster circuit  63   b  boosts an alternating voltage output from the negative electrode side inverter circuit  62   b , and boosts the alternating voltage to, for example, an alternating voltage of 4 times or more and 6 times or less, similar to the positive electrode side first booster circuit  63   a . In the present embodiment, the negative electrode side first booster circuit  63   b  boosts an alternating voltage of −48 V output from the negative electrode side inverter circuit  62   b  to an alternating voltage of −250 V. It is desirable that the alternating voltage output from the negative electrode side first booster circuit  63   b  is −60 V or more and −300 V or less. In addition, various well-known circuit configurations can be adopted as specific circuit configurations of the first booster circuit part  63 . 
     In addition, the lithium ion battery  61   a  of the electric power supply part  60  is connected to an external power source via a connector (not illustrated), and receives the supply of electric power from the external power source, and thus, the lithium ion battery  61   a  is charged. 
     The alternating voltage output from the first booster circuit part  63  of the electric power supply part  60  is supplied to the radiation generating part  50  via the cable part  70 . The cable part  70  electrically connects the electric power supply part  60  provided within the main body part  20  and the radiation generating part  50  provided at the tip of the arm part  40  to each other, and includes a positive electrode side electric power supply wiring line  70   a  and a negative electrode side electric power supply wiring line  70   b . Each of the positive electrode side electric power supply wiring line  70   a  and the negative electrode side electric power supply wiring line  70   b  is formed by covering a conductive member with an insulating member, and extends inside the supporting member  30  and inside the arm part  40 . The length of the cable part  70  is, for example, about 3 m and the wiring resistance of the cable part is, for example, about 75 mΩ. Additionally, although not illustrated, the cable part  70  includes a control signal wiring line that supplies a control signal output from the control part  22  to the radiation generating part  50 , in addition to the positive electrode side electric power supply wiring line  70   a  and the negative electrode side electric power supply wiring line  70   b.    
     The radiation generating part  50  is a so-called mono-tank in which a radiation source, a booster circuit, a voltage doubler rectifier circuit, and the like are provided within the housing  51  (refer to  FIG. 1 ). As illustrated in  FIG. 4 , the radiation generating part  50  of the present embodiment includes an X-ray tube  52  serving as a radiation source, a second booster circuit part  53 , and a voltage doubler rectifier circuit part  54 . 
     The second booster circuit part  53  boosts an alternating voltage input via the cable part  70 . Specifically, the second booster circuit part  53  includes a positive electrode side second booster circuit  53   a , and a negative electrode side second booster circuit  53   b . The positive electrode side second booster circuit  53   a  of the present embodiment boosts the alternating voltage supplied from the positive electrode side electric power supply wiring line  70   a , and boosts the alternating voltage to, for example, an alternating voltage of 50 times or more. The positive electrode side second booster circuit  53   a  of the present embodiment boosts the alternating voltage of 250 V supplied from the positive electrode side electric power supply wiring line  70   a , and boosts the alternating voltage to an alternating voltage of 12.5 kV. 
     Meanwhile, the negative electrode side second booster circuit  53   b  boosts the alternating voltage supplied from the negative electrode side electric power supply wiring line  70   b , and boosts the alternating voltage to, for example, an alternating voltage of 50 times or more, similar to the positive electrode side second booster circuit  53   a . The negative electrode side second booster circuit  53   b  of the present embodiment boosts the alternating voltage of −250 V supplied from the negative electrode side electric power supply wiring line  70   b  to an alternating voltage of −12.5 kV. In addition, various well-known circuit configurations can be adopted as specific circuit configurations of the second booster circuit part  53 . 
     Additionally, in the present embodiment, as described above, the two booster circuit parts of the first booster circuit part  63  and the second booster circuit part  53  are provided. However, the invention is not necessarily limited to such a configuration. Only one of the booster circuit parts may be provided so that an alternating voltage is boosted. 
     The voltage doubler rectifier circuit part  54  doubles and rectifies an alternating voltage output from the second booster circuit part  53 . Specifically, the voltage doubler rectifier circuit part  54  includes a positive electrode side voltage doubler rectifier circuit  54   a  and a negative electrode side voltage doubler rectifier circuit  54   b . The positive electrode side voltage doubler rectifier circuit  54   a  doubles and rectifies the alternating voltage output from the positive electrode side second booster circuit  53   a , and rectifies the alternating voltage to, for example, a positive direct current voltage of 4 times. The positive electrode side voltage doubler rectifier circuit  54   a  of the present embodiment rectifies the alternating voltage of 12.5 kV boosted by the positive electrode side second booster circuit  53   a  to a direct current voltage of 50 kV. 
     Meanwhile, the negative electrode side voltage doubler rectifier circuit  54   b  doubles and rectifies the alternating voltage output from the negative electrode side second booster circuit  53   b , and rectifies the alternating voltage to, for example, a negative direct current voltage of 4 times. The negative electrode side voltage doubler rectifier circuit  54   b  of the present embodiment rectifies the alternating voltage of −12.5 kV boosted by the negative electrode side second booster circuit  53   b  to a direct current voltage of −50 kV. In addition, the specific circuit configuration of the voltage doubler rectifier circuit part  54  is not limited to the circuit configuration illustrated in  FIG. 4 , and various well-known circuit configurations can be adopted. 
     The X-ray tube  52  generates radiation by applying a direct current voltage output from the voltage doubler rectifier circuit part  54 . In the present embodiment, as described above, the direct current voltage of 50 kV is supplied to a positive electrode side of the X-ray tube  52  by the positive electrode side voltage doubler rectifier circuit  54   a , and the direct current voltage of −50 kV is supplied to a negative electrode side of the X-ray tube  52  by the negative electrode side voltage doubler rectifier circuit  54   b . As a result, the direct current voltage of 100 kV is applied to the X-ray tube  52 . 
     The exposure switch  90  receives an emission (exposure) instruction of the radiation from the radiation generating part  50 . In addition, in the present embodiment, the exposure switch  90  is equivalent to an emission instruction receiving part of the invention. As illustrated in  FIG. 4 , the exposure switch  90  of the present embodiment includes an exposure SW 1  and an exposure SW 2 . The exposure SW 1  receives an emission preparation instruction of radiation, and the exposure SW 2  receives an emission instruction of radiation. 
     In a case where the exposure SW 1  is turned on by a user, the switch element  61   c  is turned on by the battery control part  64 , and thus, the capacitor  61   b  is charged by the lithium ion battery  61   a . Additionally, in a case where the exposure SW 2  is turned on by the user, the switch element  61   c  is turned off by the battery control part  64 , and thus, a discharge voltage is output from the capacitor  61   b.    
     In addition, in the present embodiment, the two separate switches of the exposure SW 1  and the exposure SW 2  are provided. However, the configuration of the exposure switch  90  is not limited to this. For example, a switch that receives two push states of half push and full push may be used, a switch element  61   c  may be turned on in the case of the half push, and the switch element  61   c  may be turned off in the case of the full push. 
     Additionally, the exposure switch  90  may be provided in an input part  24  in the monitor  23  to be described below, or may be provided separately from the monitor  23 . 
     Additionally, in the present embodiment, charging to the capacitor  61   b  by the lithium ion battery  61   a  and discharging from the capacitor  61   b  are switched therebetween according to the operation of the exposure SW 1  and the exposure SW 2  by a user. However, the invention is not limited to this. A control function of switching the connection between the lithium ion battery  61   a  and the capacitor  61   b  by determining an imaging menu registered by an engineer may be added. As the imaging menu, for example, there is an imaging menu for performing short-time X-ray imaging multiple times in a short time. In a case where this imaging menu is selected, it is desirable to perform discharging from the capacitor  61   b  to perform radiation exposure, in a state where the lithium ion battery  61   a  and the capacitor  61   b  are connected, that is, in a charging state. In addition, in this case, it is desirable to design the capacity of the capacitor  61   b  such that a voltage drop on an electric power supply side occurring at the time of the discharging from the capacitor  61   b  falls within a usable range of the lithium ion battery  61   a.    
     Additionally, the battery control part  64  monitors a terminal voltage of the capacitor  61   b . Then, in a case where the switch element  61   c  is turned on to charge the capacitor  61   b  and the terminal voltage of the capacitor  61   b  becomes equal to or more than a preset threshold value, a light-emitting part  91  is caused to emit light. By emitting light from the light-emitting part  91 , it is possible to notify a user that the charging of the capacitor  61   b  is completed. Hence, the user can check light emission of the light-emitting part  91  to turn on the exposure SW 2 , and can efficiently perform the charging to the capacitor  61   b  and the exposure of radiation. As the light-emitting part  91 , for example, a light emitting diode (LED) can be used. In addition, in the present embodiment, the light-emitting part  91  is caused to emit light by monitoring the terminal voltage of the capacitor  61   b . However, the invention is not limited to this. For example, the light-emitting part  91  may be caused to emit light in a case where the time after the exposure SW 1  is turned on is measured and the measured time becomes equal to or more than a preset threshold value. Although a threshold value of the measured time also depends on a charging speed to the capacitor  61   b  and the capacity of the capacitor  61   b , it is desirable that the threshold value is 0.8 seconds or more and 4 seconds or less. 
     Additionally, in the above description, the light-emitting part  91  is turned on in a case where the charging of the capacitor  61   b  is completed. However, the light-emitting part  91  may be caused to emit light not only in the case where the charging to the capacitor  61   b  is completed but also in a case where it is detected that, for example, other radiation exposure preparation operations, such as voltage application to a filament, are completed. 
     Additionally, in the present embodiment, the light-emitting part  91  is equivalent to a notification part of the invention. However, the configuration of the notification part is not limited to this. For example, when the charging of the capacitor  61   b  is completed, sound may be emitted, or a message may be displayed on the monitor  23 . 
     Here, the operation of the radiation irradiation device  1  from the charging to the capacitor  61   b  of the battery part  61  to the exposure of radiation will be described, referring to a timing chart illustrated in  FIG. 5 . 
     First, the exposure SW 1  is turned on by a user, and accordingly, the switch element  61   c  is turned on and the charging of the capacitor  61   b  is started. In a case where the charging of the capacitor  61   b  proceeds and the terminal voltage of the capacitor  61   b  becomes equal to or more than a threshold value of a voltage, the light-emitting part  91  is controlled by the battery control part  64 , and the light-emitting part  91  is turned on. 
     Then, the user turns on the exposure SW 2  after ON of the light-emitting part  91  is checked. The switch element  61   c  is turned off by ON state of the exposure SW 2 , and thus, the discharge voltage of the capacitor  61   b  is supplied to the radiation generating part  50  and radiation is radiated from the radiation generating part  50 . 
     In addition, as for the battery part  61 , a diode element  61   d  may be further provided, as illustrated in  FIG. 6 , such that the electric charge charged by the capacitor  61   b  does not flow back to the lithium ion battery  61   a  side. Although the diode element  61   d  is equivalent to a reverse current suppressing part of the invention, the reverse current suppressing part is not limited to the diode element  61   d , and other well-known elements or circuits can be used. 
     Additionally, in order to reduce an inrush current when charging the capacitor  61   b  from the lithium ion battery  61   a , current limiting may be performed. Specifically, a gate voltage to be applied to the switch element  61   c  by the battery control part  64  may be gradually increased according to the lapse of time, as illustrated by a solid line of  FIG. 7 . By controlling the waveform of the gate voltage as illustrated by a solid line of  FIG. 7 , the waveform of a current flowing into the capacitor  61   b  can be controlled as illustrated by a dotted line of  FIG. 7 , and the inrush current to the capacitor  61   b  can be suppressed. 
     Additionally, in a case where a relay switch is used as the switch element  61   c , in order to reduce the inrush current when the capacitor  61   b  is charged from the lithium ion battery  61   a , a resistance element  61   e  may be connected to the capacitor  61   b  in series, as illustrated in  FIG. 8 . 
     In addition, although the battery control part  64  and the resistance element  61   e  that apply the above-described gate voltage are equivalent to an inrush current suppressing part of the invention, the inrush current suppressing part is not limited to this, and other well-known elements or well-known circuits be used. 
     Returning to  FIGS. 1 and 2 , an L-shaped radiation source attachment part  32  is provided at a tip (one end) of the arm part  40 . The radiation generating part  50  is attached to the one end of the arm part  40  via the radiation source attachment part  32 . As illustrated in  FIGS. 1 and 2 , the cable part  70  taken out from the one end of the arm part  40  is connected to the radiation generating part  50  via a connector. 
     The radiation generating part  50  is connected to the radiation source attachment part  32  so as to be rotationally movable with an axis AX 2  as a rotational movement axis. The rotational movement axis AX 2  is an axis that extends in the leftward-rightward direction (x direction). In addition, the radiation source attachment part  32  holds the radiation generating part  50  such that the radiation generating part  50  moves rotationally via a friction mechanism. For this reason, the radiation generating part  50  is rotationally movable by applying a certain degree of strong external force, does not move rotationally unless an external force is applied, and maintains a relative angle with respect to the arm part  40 . 
     Additionally, the monitor  23  is attached to an upper surface of the housing  21 . Additionally, a handle part  26  for pushing or pulling the radiation irradiation device  1  is attached to an upper part of the housing  21 . The handle part  26  is provided so as to go around the housing  21 , and is configured so as to be capable of being held not only from a rear side of the radiation irradiation device  1  but also from a front side or a lateral side.  FIG. 9  is a view of the radiation irradiation device  1  as seen from the front. As illustrated in  FIG. 9 , the handle part  26  is provided so as to go around to a front side of the main body part  20 . 
     The monitor  23  consists of a liquid crystal panel or the like, and displays a radiation image acquired by imaging of a subject, and various kinds of information required for the control of the radiation irradiation device  1 . Additionally, the monitor  23  includes the touch panel type input part  24 , and receives input of various instructions required for the operation of the radiation irradiation device  1 . Specifically, input for setting of imaging conditions and input for imaging, that is, emission of radiation, can be received. The monitor  23  is attached to the upper surface of the housing  21  so as to be capable of changing the inclination and the rotational position of a display surface with respect to the horizontal direction. Additionally, instead of the touch panel type input part  24 , buttons for performing various operations may be included as the input part. 
     One end of the supporting member  30  is connected to the other end of the arm part  40 . The arm part  40  is connected to the supporting member  30  so as to be rotationally movable with an axis AX 1  as a rotational movement axis. The rotational movement axis AX 1  is an axis that extends in the leftward-rightward direction (x direction). The arm part  40  moves rotationally in a direction of arrow A illustrated in  FIG. 2  such that an angle formed with the supporting member  30  is changed about the rotational movement axis AX 1 . 
     A rotational movement part  31  having the rotational movement axis AX 1  holds the arm part  40  such that the arm part  40  moves rotationally via the friction mechanism. For this reason, the arm part  40  is rotationally movable by applying a certain degree of strong external force, does not move rotationally unless an external force is applied, and maintains a relative angle with respect to the supporting member  30 . 
     In addition, although the rotational movement of the arm part  40  and the radiation generating part  50  is performed via the friction mechanism, rotational movement positions of these parts may be fixed by a well-known locking mechanism. In this case, the rotational movements of the arm part  40  and the radiation generating part  50  become possible by releasing the locking mechanism. The rotational movement positions can be fixed by locking the locking mechanism at desired rotational movement positions. 
     The other end of the supporting member  30  is connected to the surface of the main body part  20  on the front side. The supporting member  30  is provided so as to be fixed with respect to the main body part  20 , and is attached so as to be non-rotatable with respect to the main body part  20 . In the present embodiment, as described above, the orientation of the arm part  40  can be freely changed together with the main body part  20  by the revolution of the first casters  10   a  and the second casters  10   b . Thus, it is not necessary to make the supporting member  30  have a degree of freedom, and a simpler configuration can be adopted. However, the invention is not limited to this, and the supporting member  30  may be configured to rotate with emphasis on handleability. That is, the supporting member  30  may be configured so as to be rotatable with an axis passing through the center of the portion of the supporting member  30  connected to the main body part  20  and extending in the vertical direction as a rotation axis. 
     In the present embodiment, when a subject is imaged, as illustrated in  FIG. 2 , the imaging is performed by arranging a radiation detector  80  under a subject H that lies on ones&#39; back on a bed  3  and irradiating the subject H with the radiation emitted from the radiation generating part  50 . In addition, the radiation detector  80  and the radiation irradiation device  1  are connected together with or without wires. Accordingly, the radiation image of the subject H acquired by the radiation detector  80  is directly input to the radiation irradiation device  1 . 
     Here, a radiation detector  80  will be briefly described with reference to  FIG. 10 .  FIG. 10  is an external perspective view of the radiation detector as seen from a front surface that is a radiation detection surface side. As illustrated in  FIG. 10 , the radiation detector  80  is a cassette type radiation detector including a housing  82  that has a rectangular flat plate shape and houses a detecting part  81 . The detecting part  81  includes a scintillator (fluorescent body) that converts incident radiation into visible light as is well known, and a thin film transistor (TFT) active matrix substrate. A rectangular imaging region where a plurality of pixels that accumulate electrical charge according to the visible light from the scintillator are arrayed is formed on the TFT active matrix substrate. 
     Additionally, the housing  82  includes a round-chamfered metallic frame. A gate driver that gives a gate pulse to a gate of a TFT to switch the TFT, an imaging control part including a signal processing circuit that converts an electrical charge accumulated in a pixel into an analog electrical signal representing an X-ray image to output the converted signal, and the like in addition to the detecting part  81  are built in the housing. Additionally, the housing  82  has, for example, a size based on International Organization for Standardization (ISO) 4090:2001 that is substantially the same as a film cassette, an imaging plate (IP) cassette, and a computed radiography (CR) cassette. 
     A transmission plate  83  that allows radiation to be transmitted therethrough is attached to a front surface of the housing  82 . The transmission plate  83  has a size that substantially coincides with a detection region of radiation in the radiation detector  80 , and is formed of a carbon material that is lightweight, has high rigidity, and has high radiation transmissivity. In addition, the shape of the detection region is the same oblong shape as the shape of the front surface of the housing  82 . Additionally, the portion of the frame of the housing  82  protrudes from the transmission plate  83  in a thickness direction of the radiation detector  80 . For this reason, the transmission plate  83  is not easily damaged. 
     Markers  84 A to  84 D showing identification information for identifying the radiation detector  80  are applied to four corners of the front surface of the housing  82 . In the present embodiment, the markers  84 A to  84 D consist of two bar codes that are orthogonal to each other, respectively. 
     Additionally, a connector  85  for charging the radiation detector  80  is attached to a side surface of the housing  82  on the markers  84 C,  84 D side. 
     When the radiation irradiation device  1  according to the present embodiment is used, the operator rotationally moves the arm part  40  around the rotational movement axis AX 1  in an illustrated counterclockwise direction from an initial position of the arm part  40  illustrated in  FIG. 1 , and thus, the radiation generating part  50  is moved to a target position immediately above the subject H, as illustrated in  FIG. 2 . The radiation image of the subject H can be acquired by driving the radiation generating part  50  according to an instruction from the input part  24  to irradiate the subject H with radiation and detecting the radiation transmitted through the subject H, using the radiation detector  80 , after the radiation generating part  50  is moved to the target position. 
     In addition, as the radiation detector  80 , as described above, it is desirable to use a radiation detector in which the scintillator and the TFT active matrix substrate including light receiving elements are laminated and which receives irradiation of radiation from a TFT active matrix substrate side (a side opposite to a scintillator side). By using such a high-sensitivity radiation detector  80 , a low-output radiation source can be used as the radiation generating part  50 , and the weight of the radiation generating part  50  can be made light. In addition, generally, the radiation source output of the radiation generating part  50  and the weight of the radiation generating part  50  are in a proportional relation. 
     Since the weight of the radiation generating part  50  can be made light as described above, the total weight of the radiation irradiation device  1  can also be made light. Accordingly, by using the revolving casters as the second caster  10   b  (rear wheels) as in the radiation irradiation device  1  of the present embodiment, the revolution performance of the radiation irradiation device  1  can be improved, and handling can be markedly improved. 
     In addition, the radiation source output of the radiation generating part  50  is preferably 15 kW or less, and is more preferably 4 kW or less. Additionally, the total weight of radiation irradiation device  1  is preferably 120 kg or less, and is more preferably 90 kg or less. 
     Next, a configuration in which the radiation detector  80  in the main body part  20  is capable of being housed will be described. As illustrated in  FIGS. 1 and 2 , the housing  21  of the main body part  20  has a flat surface  21   a  inclined to a supporting member  30  side, on a surface opposite to a side where the supporting member  30  is attached, and the flat surface  21   a  is provided with the cradle  25 . 
     An insertion port  25   a  for inserting the radiation detector  80  is formed in an upper surface of the cradle  25 . The insertion port  25   a  has an elongated shape of a size such that the radiation detector  80  is fitted thereto. In the present embodiment, one end part on a side having the connector  85  of the radiation detector  80  is inserted to the insertion port  25   a . Accordingly, this one end part is supported by a bottom part of the cradle  25 , and the radiation detector  80  is held by the cradle  25 . In this case, a front surface of the radiation detector  80  is directed to a flat surface  21   a  side. 
     A connector  25   b  is attached to the bottom part of the cradle  25 . The connector  25   b  is electrically connected to the connector  85  of the radiation detector  80  when the radiation detector  80  is held by the cradle  25 . The connector  25   b  is electrically connected to the lithium ion battery  61   a  of the battery part  61 . Hence, when the radiation detector  80  is held by the cradle  25 , the radiation detector  80  is charged by the lithium ion battery  61   a  via the connector  85  of the radiation detector  80  and the connector  25   b  of the cradle  25 . 
     In addition, a configuration in which the radiation detector  80  is chargeable by the lithium ion battery  61   a  has been described in the present embodiment. As described above, a configuration in which the monitor  23  is chargeable by the lithium ion battery  61   a  may be adopted. Moreover, a configuration in which an external connector is further provided at the main body part  20  and external instruments other than the monitor are connectable may be adopted. Also, a configuration in which electric power is supplied to an external instrument by the lithium ion battery  61   a  via the external connector and the external instrument is chargeable may be adopted. As the external instrument, for example, there is a note-type computer used as a console, or the like. 
     In addition, the radiation irradiation device of the invention does not necessarily include the leg part  10  as in the radiation irradiation device  1  of the above embodiment. Additionally, the configuration of the supporting member  30  and the arm part  40  is not limited to the configuration of the above embodiment, and other configurations may be adopted. 
     EXPLANATION OF REFERENCES 
     
         
         
           
               1 : radiation irradiation device 
               2 : device placement surface 
               3 : bed 
               10 : leg part 
               10   a : first caster 
               10   b : second caster 
               11 : pedestal part 
               12 : foot arm part 
               12   a : tip part 
               13 : pedal part 
               13   a : first pedal 
               13   b : second pedal 
               20 : main body part 
               21 : housing 
               21   a : flat surface 
               22 : control part 
               23 : monitor 
               24 : input part 
               25 : cradle 
               25   a : insertion port 
               25   b : connector 
               26 : handle part 
               30 : supporting member 
               31 : rotational movement part 
               32 : radiation source attachment part 
               40 : arm part 
               50 : radiation generating part 
               51 : housing 
               52 : X-ray tube 
               53 : second booster circuit part 
               53   a : positive electrode side booster circuit 
               53   b : negative electrode side booster circuit 
               54 : voltage doubler rectifier circuit part 
               54   a : positive electrode side voltage doubler rectifier circuit 
               54   b : negative electrode side voltage doubler rectifier circuit 
               60 : electric power supply part 
               61 : battery part 
               61   a : lithium ion battery 
               61   b : capacitor 
               61   c : switch element 
               61   d : diode element 
               61   e : resistance element 
               62 : inverter circuit part 
               62   a : positive electrode side inverter circuit 
               62   b : negative electrode side inverter circuit 
               63 : first booster circuit part 
               64 : battery control part 
               70 : cable part 
               70   a : positive electrode side electric power supply wiring line 
               70   b : negative electrode side electric power supply wiring line 
               80 : radiation detector 
               81 : detecting part 
               82 : housing 
               83 : transmission plate 
               85 : connector 
               90 : exposure switch 
               91 : light-emitting part 
             AX 1 : rotational movement axis 
             AX 2 : rotational movement axis 
             H: subject 
               84 A to  84 D: marker