Patent Publication Number: US-2022218299-A1

Title: X-ray fluoroscopic imaging apparatus and x-ray fluoroscopy imaging process

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The related application No. JP2021-004449, entitled “X-Ray Fluoroscopic Imaging Apparatus and X-Ray Fluoroscopy Imaging Method,” filed on Jan. 14, 2021, invented by Koki YOSHIDA, and Fumiaki TANAKA, upon which this patent application is based is hereby incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an X-ray fluoroscopic imaging apparatus and an X-ray fluoroscopic imaging method. In particular, the present invention relates to an X-ray fluoroscopic imaging apparatus equipped with a storage unit for storing a plurality of target positions serving as targets toward which an imaging unit is moved and the order of moving the imaging unit toward the plurality of target positions in an associated manner, and also related to an X-ray fluoroscopic imaging method. 
     Description of the Background Art 
     Conventionally, an X-ray fluoroscopic imaging apparatus equipped with a storage unit for storing a plurality of target positions serving as targets toward which the imaging unit is moved and the order of moving the imaging unit toward the plurality of target positions in an associated manner is known. Such an apparatus is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2000-197621. 
     The medical imaging apparatus described in Japanese Unexamined Patent Application Publication No. 2000-197621 is provided with: an imaging means for imaging a medical image relating to a subject; a support mechanism for supporting the imaging means at various positions; a means for storing a plurality of positions of the imaging means and the order as data in an associated manner; and a control means for controlling the support mechanism in accordance with the stored positions and the order to sequentially change the position of the imaging means. 
     In the medical imaging apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2000-197621, the control means is configured to move the imaging means to stored positions in accordance with sequential positioning data composed of data of the positions of the imaging means stored in the storing means and the order. When the next positioning switch is pressed after completion of the imaging, the control unit reads out the data relating to the next position from the storing means and moves the imaging unit to the next position. 
     Here, although not described in the above-described Japanese Unexamined Patent Application Publication No. 2000-197621, imaging is sometimes performed by finely adjusting the imaging position because there is an individual difference depending on a subject. Further, in some cases, imaging is performed at a position not stored during a series of imaging at each imaging position. 
     However, in the X-ray fluoroscopic imaging apparatus configured to read out the data of the next imaging position when the imaging unit has moved to the position stored in the storage unit, there are the following issues. That is, in a case where imaging has been performed by stopping the imaging unit between the current position and the next position, or in a case where imaging has been performed at a position not stored, there are the following problems. That is, the next imaging position will not be read because the movement of the imaging unit has not yet been completed. Further, since the next imaging position is not read, the next imaging position (target position) must be selected again, and then the positioning switch must be pressed again. 
     SUMMARY OF THE INVENTION 
     The present invention has been made to solve the above-described problems. It is an object of the present invention to provide an X-ray fluoroscopic imaging apparatus capable of switching the imaging position to the next target position without selecting the next target position when imaging has been performed at any imaging position. 
     In order to attain the above-described objects, an X-ray fluoroscopic imaging apparatus according to one aspect of the present invention includes: a bed configured to place a subject thereon; an imaging unit including an X-ray source for irradiating the subject with X-rays, a detector for detecting X-rays emitted from the X-ray source, the detector facing the X-ray source, and an arm for connecting the X-ray source and the detector; a storage unit configured to store a plurality of target positions serving as targets toward which the imaging unit is moved and an order of moving the imaging unit to the plurality of target positions in an associated manner; a control unit configured to sequentially switch the plurality of target positions according to the order; and a drive unit configured to move the imaging unit toward a target position switched by the control unit. The control unit includes a first determination unit configured to determine whether or not X-ray imaging has been performed. When it is determined by the first determination unit that X-ray imaging has been performed, the control unit is configured to perform control to switch the target position to a next target position. 
     In the X-ray fluoroscopic imaging apparatus according to the above-described one aspect of the present invention, the control unit includes a first determination unit for determining whether or not X-ray imaging has been performed and is configured to perform control to switch the imaging position to the next target position when it is determined by the first determination unit that X-ray imaging has been performed. Thus, when it is determined by the first determination unit that X-ray imaging has been performed, the control unit performs control to switch the imaging position to the next target position. With this, when the imaging is completed regardless of the position of the imaging unit after moving, the control unit performs control to switch the target position. For this reason, the target position can be switched even in a case where imaging has been performed at a position other than the target position. Consequently, when imaging has been performed at any imaging position, the imaging position can be switched to the next target position without selecting the next imaging position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram for explaining the configuration of an X-ray fluoroscopic imaging apparatus. 
         FIG. 2A  is a schematic diagram for explaining imaging directions as viewed from the side of the subject. 
         FIG. 2B  is a schematic diagram for explaining imaging directions as viewed from the foot side of the subject. 
         FIG. 3  is a diagram for explaining relative positions between a bed and an imaging unit. 
         FIG. 4  is a block diagram showing the configuration of the control unit of the X-ray imaging apparatus. 
         FIG. 5  is a diagram for explaining the configurations of a rotation mechanism and a moving mechanism of the imaging unit. 
         FIG. 6  shows an example of target positions displayed on a display unit. 
         FIG. 7A  is a diagram for explaining the rotation of an arm about a rotating axis by a rotation mechanism when imaging at an RAO position. 
         FIG. 7B  is a diagram for explaining the rotation of an arm about a rotating axis by a rotation mechanism when imaging at an LAO position. 
         FIG. 8A  is a diagram for explaining a circumferential rotation of an arm by a rotation mechanism when imaging at a CRANIAL position. 
         FIG. 8B  is a diagram for explaining a circumferential rotation of an arm by a rotation mechanism when imaging at a CAUDAL position. 
         FIG. 9  is a flowchart showing an example of control by a control unit in a sequence mode. 
         FIG. 10  is a flowchart showing an example of movement control of an imaging unit. 
         FIG. 11  is a flowchart showing an example of control by a control unit in a sequence mode according to a first modification. 
         FIG. 12  is a diagram showing an example of target positions displayed on a display unit according to a second modification. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, an embodiment in which the present invention is embodied will be described with reference to the attached drawings. 
     Overall Configuration of X-Ray Fluoroscopic Imaging Apparatus 
     Referring to  FIG. 1  to  FIG. 8 , an X-ray fluoroscopic imaging apparatus  100  according to an embodiment of the present invention will be described. 
     As shown in  FIG. 1 , the X-ray fluoroscopic imaging apparatus  100  is a device for diagnosing a disease in a target site of a subject  50 . The target site is, for example, a blood vessel (coronary artery) of a heart but may also be an abdomen or a lower limb. 
     The X-ray fluoroscopic imaging apparatus  100  according to this embodiment is provided with a bed  1 , an imaging unit  2 , a storage unit  3 , a control unit  4 , an operation unit  5 , a drive unit  6 , and a position information acquisition unit  7 . The X-ray fluoroscopic imaging apparatus  100  sequentially images the target sites at a plurality of angles and positions based on a plurality of target positions  40  stored in the storage unit  3 . 
     Note that, in this embodiment, the mode in which the X-ray fluoroscopic imaging apparatus  100  sequentially images the target sites based on the plurality of target positions  40  stored in the storage unit  3  at the plurality of angles and positions will be referred to as a sequence mode. 
     The bed  1  includes a top board  11  configured to place a subject  50  thereon and a base  12  configured to support the bed  1  from below. The subject  50  is laid on the top board  11  such that the longitudinal direction of the bed  1  (top board  11 ) and the head-to-foot direction of the subject  50  coincide. Here, in the state shown in  FIG. 1 , the longitudinal direction of the bed  1  is defined as an X-direction. Further, the side on which the head of the subject  50  is placed is defined as an X 1  side, and the side on which the foot is placed is defined as an X 2  side. The short direction (left-right direction of the subject  50 ) of the bed  1  perpendicular to the X-direction is defined as a Y-direction. The right hand side of the subject  50  when the subject  50  lies on the back is defined as a Y 1  side, and the left hand side is defined as a Y 2  side. Further, the up-down direction of the bed  1  orthogonal to the X-direction and the Y-direction is defined as a Z-direction. Further, the top board  11  side is defined as a Z 1  side, and the base  12  side is defined as a Z 2  side. The base  12  is provided at a part of the bottom surface side (Z 2  side) of the bed  1 . 
     The imaging unit  2  is provided with an X-ray source  21 , a detector  22 , and an arm  23 . The X-ray source  21  includes an X-ray tube (not shown). The X-ray tube is configured to heat an anode and a cathode therein by passing a current therethrough and emit X-rays when the thermal electrons ejected from the cathode by applying a voltage between the anode and the cathode collide against the anode. Further, it is configured such that the X-rays generated by the X-ray tube are emitted toward the detector  22 . When the tube voltage applied to the X-ray tube is changed, the X-ray fluoroscopic dose (irradiation intensity) of the X-rays to be emitted is determined according to the tube voltage. Further, the X-ray source  21  is configured to transmit a signal to the control unit  4  while emitting X-rays. 
     The detector  22  is, for example, an FPD (Flat Panel Detector). The detector  22  is configured to receive the X-rays emitted from the X-ray source  21  and transmitted through the subject  50 , and converts the received X-rays into an electric signal. The detector  22  has an imaging element (not shown) having a plurality of pixels (zones) therein, detects the intensity of the X-rays for each corresponding pixel, and converts the X-ray information (detection signal) for each pixel into an electric signal (digital data) as a pixel value. The X-ray information converted into an electric signal is transmitted to the control unit  4 . 
     The arm  23  has an arcuate shape. The X-ray source  21  is connected to one end of the arm  23 , and the detector  22  is connected to the other end of the arm  23 . The arm  23  is a so-called C-shaped arm. By means of the arm  23 , the X-ray source  21  and the detector  22  are arranged so as to face each other across the subject  50  lying on the bed  1 . The base  12  of the bed  1  is provided only at a part of the top board  11 . Therefore, it is possible to insert the arm  23  at the portion not provided with the base  12  to thereby place the X-ray source  21  on the bottom surface side of the bed  1  (Z 2  side). In this embodiment, the X-ray fluoroscopic imaging apparatus  100  is a single-plane type equipped with a single arm  23 . 
     The arm  23  is rotatably mounted on the arm base  24 . The arm base  24  is provided with a rotation mechanism  61  for rotating the arm  23  therein. Note that the rotation mechanism  61  is an example of the “drive unit” recited in claims. 
     The imaging unit  2  is configured to perform imaging from the following directions. That is, the imaging unit  2  is configured to perform imaging from any direction in which a direction along which X-rays are emitted obliquely with respect to the subject  50  from one end side (CRANIAL side) or the other end side (CAUDAL side) in a longitudinal cross-section along the longitudinal direction (X-direction) of the bed  1  for placing the subject  50  thereon as shown in  FIG. 2A , the RAO (right anterior oblique) direction, the front direction, and the LAO (left anterior oblique) direction of the subject  50  are combined. Note that the illustration of the arm  23  is omitted in  FIG. 2B . 
     As shown in  FIG. 3 , the relative position of the imaging unit  2  with respect to the bed  1  differs depending on the site to be imaged. In  FIG. 3 , the direction of the arrow indicates the direction of inserting the imaging unit  2  between the top board  11  of the bed  1  and the floor. The detector  22  is positioned on the tip end side of the arrow, which is the subject  50  side, and the arm base  24  is positioned on the base end side of the arrow opposite to the tip end side. The position in which the arm  23  is positioned along the longitudinal direction (X-direction) of the bed  1  on the top view is referred to as a “HOME position.” The position in which the arm  23  is arranged obliquely from the head side (X 1  side) toward the foot side (X 2  side) of the subject  50  and from the peripheral portion of the bed  1  in the longitudinal direction (X-direction) toward the subject  50  is referred to as a “MULTI position.” The position in which the arm  23  is arranged along the short direction (Y-direction) of the bed  1  from the side of the subject  50  toward the center thereof in the top view is referred to as a “SIDE position.” In addition, the position moved from the SIDE position to the foot side (X 2  side) of the subject  50  is referred to as a “PERI position.” For example, in the case of imaging from the head to the chest of the subject  50 , the arm  23  is set to the HOME position. In the case of imaging the lower limb, the arm  23  is set to the PERI position. Further, in the case of imaging the abdomen of the subject  50 , the arm  23  is set to the MULTI position or the SIDE position. 
     As shown in  FIG. 1 , the storage unit  3  stores a plurality of target positions  40  toward which the imaging unit  2  is moved and the order of moving the imaging unit toward the plurality of target positions  40  in an associated manner. The storage unit  3  is, for example, an HDD (Hard Disk Drive) or a nonvolatile memory. 
     The control unit  4  controls the imaging unit  2  to image the subject  50  based on the operation via the operation unit  5 . Further, the control unit  4  performs control to make the storage unit  3  store target positions  40 . Further, the control unit  4  performs control to make the display unit  8  display an image. The control unit  4  is, for example, a CPU (Central Processing Unit). 
     As shown in  FIG. 4 , the control unit  4  composed of a CPU or the like as hardware includes a first determination unit  41  and a second determination unit  42  as functional blocks of the software. The first determination unit  41  determines whether or not X-ray imaging has been performed. The second determination unit  42  determines whether or not the current position information on the imaging unit  2  acquired by the position information acquisition unit  7  matches the currently selected target position  40 . The control unit  4  performs control to sequentially switch a plurality of target positions  40 . Further, the control unit  4  performs control to sequentially move the imaging unit  2  toward the plurality of target positions  40  stored in the storage unit  3  based on the operation of moving the imaging unit  2 . Specifically, the control unit  4  moves (rotates) the imaging unit  2  by controlling the rotation mechanism  61  (see  FIG. 1 ) to rotate the arm  23 . 
     The first determination unit  41  determines whether or not X-ray imaging has been performed. Specifically, the first determination unit  41  determines whether or not X-ray imaging has been performed based on the signal transmitted from the X-ray source  21  to the control unit  4  during the X-ray irradiation. 
     The second determination unit  42  determines whether or not the current position information on the imaging unit  2  matches the currently selected target position  40 . Specifically, the second determination unit  42  compares the current absolute position of the imaging unit  2  acquired by the position information acquisition unit  7  with the absolute position of the imaging unit  2  at the target position  40 . The absolute position is determined, for example, by the position coordinate. 
     In a case where the second determination unit  42  has determined that the current position information on the imaging unit  2  does not match the currently selected target position  40 , i.e., even in a case where the imaging unit  2  after moving has not reached the target position  40 , it is determined by the first determination unit  41  that imaging has been completed and the imaging has been performed. With this, the control unit  4  performs control to sequentially switch the plurality of target positions  40 . Further, the control unit  4  performs control to switch the target positions  40  upon receipt of the imaging operation via the operation unit  5 . Further, when the imaging unit  2  has been moved manually, the control unit  4  performs control to terminate the sequence mode. Note that, when the sequence mode has been terminated, the control unit  4  performs control to set the selected target position  40  to a new target position  40  upon receipt of the operation of selecting a target position  40 . 
     As shown in  FIG. 1 , the operation unit  5  includes a first operation unit  51 , a second operation unit  52 , and a third operation unit  53 . The first operation unit  51  receives an operation of moving the imaging unit  2  toward the target position  40 . The second operation unit  52  receives an operation of moving the imaging unit  2  in a direction different from a direction toward the target position  40 . The third operation unit  53  receives an imaging operation. The operation unit  5  is arranged on the side (Y-direction side) of the bed  1 . 
     When the first operation unit  51  is operated, the control unit  4  controls the rotation mechanism  61  and the moving mechanism  62  to rotate or move the arm  23  to thereby move the imaging unit  2  toward the target position  40 . Further, when the operation of the first operation unit  51  has been terminated, even if the imaging unit  2  has not yet reached the target position  40 , the control unit  4  terminates the control to move the imaging unit  2  toward the target position  40 . Furthermore, in a case where the imaging unit  2  has not yet reached the target position  40  and the first operation unit  51  is again operated after the stop of the movement of the imaging unit  2  toward the target position  40 , the control unit  4  controls as follows. That is, the control unit  4  controls the rotation mechanism  61  and the moving mechanism  62  to rotate or move the arm  23  to thereby move the imaging unit  2  toward the target position  40 . The first operation unit  51  is, for example, a push button. Note that the moving mechanism  62  is an example of the “drive unit” recited in claims. 
     When the second operation unit  52  is operated, the control unit  4  controls the rotation mechanism  61  and the moving mechanism  62  to rotate or move the arm  23  to thereby move the imaging unit  2  in a direction different from a direction toward the target position  40 . The second operation unit  52  is, for example, a lever switch. In this case, the control unit  4  controls the rotation mechanism  61  and the moving mechanism  62  to rotate or move the arm  23  toward the inclination direction of the lever switch. 
     When the third operation unit  53  is operated, the control unit  4  controls the imaging unit  2  to image the subject  50 . The third operation unit  53  is, for example, a foot switch or a hand switch. 
     The first operation unit  51 , the second operation unit  52 , and the third operation unit  53  may be provided on one console or may be arranged independently. For example, in a case where the third operation unit  53  is configured by a foot switch, the first operation unit  51  and the second operation unit  52  may be provided on a single console. In a case where the third operation unit  53  is configured by a hand switch, the first operation unit  51 , the second operation unit  52 , and the third operation unit  53  may be provided on a single console. 
     As shown in  FIG. 1 , the drive unit  6  includes a rotation mechanism  61  and a moving mechanism  62 . As shown in  FIG. 5 , the rotation mechanism  61  rotates the arm  23  about the axis of a rotating shaft  611 , which is a line extending in the longitudinal direction (X-direction) of the bed  1  connecting the head and the foot of the subject  50 . Further, the rotation mechanism  61  is configured to rotate the arm  23  in the circumferential direction  612  of the arm  23 . In this embodiment, the angle at which the arm  23  rotates about the axis of the rotating axis  611  is referred to as a first rotation angle  25  (see  FIG. 7A  and  FIG. 7B ). Further, the angle at which the arm  23  is rotated in the circumferential direction  612  of the arm  23  is referred to as a second rotation angle  26  (see  FIG. 8A  and  FIG. 8B ). The rotation mechanism  61  includes, for example, a motor and the like. 
     The moving mechanism  62  is attached to the arm base  24 . With the moving mechanism  62 , it is possible to move the arm  23  horizontally by moving the arm base  24 . The moving mechanism  62  includes a first rotation unit  621  provided on a floor  90  and a second rotation unit  622  rotatably held by the first rotation unit  621  to rotatably hold the arm base  24 . The first rotation unit  621  includes a base axis  623  and an intermediate axis  624  provided at a position away from the base axis  623 . The second rotation unit  622  includes a horizontal rotation axis  625 . 
     The base axis  623  and the intermediate axis  624  are each a rotation axis oriented in the vertical direction with respect to the floor  90 . Further, the horizontal rotation axis  625  is a rotation axis oriented in the vertical direction with respect to the floor  90 . This allows the moving mechanism  62  to combine the rotation about the base axis  623 , the rotation about the intermediate axis  624 , and the rotation about the horizontal rotation axis  625  to move the arm base  24  and the arm  23  horizontally to a desired position. 
     The position information acquisition unit  7  acquires the current position of the imaging unit  2 . Specifically, the position information acquisition unit  7  acquires the absolute position of the imaging unit  2  and the absolute position of the top board  11 . 
     As shown in  FIG. 1 , the X-ray fluoroscopic imaging apparatus  100  of this embodiment further includes a display unit  8 . The display unit  8  is provided on the side (Y-direction side) of the bed  1 . The display unit  8  displays a plurality of target positions  40 . The display unit  8  is a touch panel liquid crystal monitor for receiving the operator&#39;s operation. The control unit  4  performs control to make the display unit  8  display the current target position  40  in a manner different from the other target positions  40 . In this case, the control unit  4  controls, for example, to distinguish the color from the colors of the other target positions  40  with the current target position  40  surrounded by a frame. Alternatively, the control unit  4  performs control to blink the current target position  40 . In  FIG. 6 , an example is shown in which the current target position  40  is surrounded by a hatched frame. 
     When one of the target positions  40  on the display unit  8  is selected, the target position  40  is switched to the selected target position  40 . Therefore, it becomes possible to perform imaging by skipping the imaging of unnecessary target positions  40 . Further, by selecting the same target position  40 , imaging at the same position can be repeated. The control unit  4  perform control to make the display unit  8  display a plurality of target positions  40  in a list format. Further, the control unit  4  performs control to display a plurality of target positions  40  on the display unit  8  in order. For example, the control unit  4  performs control to make the display unit  8  display a plurality of target positions  40  in the sequential order from the top. 
     The target position  40  is a position where one target site of a subject  50  registered in advance is imaged at a plurality of angles. The target position  40  includes a rotation angle of the arm  23 , a relative position of the arm  23  with respect to the top board  11  of the bed  1 , and the distance between the focal position of the X-ray source  21  and the detector  22 . 
     As shown in  FIG. 2 , the rotation angle of the arm  23  is a combination of an angle for rotating the arm  23  by the rotation mechanism  61  when imaging is performed at either the RAO position or the LAO position and an angle for rotating the arm  23  when imaging is performed either at the CRANIAL position or the CAUDAL position. 
     As shown in  FIG. 6 , a plurality of target positions  40  is displayed on the display unit  8 . The numerals “01,” “02,” “03,” and “04” among the target positions  40  each show the order of moving the imaging unit  2  toward the target positions  40 . Also, “RAO” and “LAO” indicate that imaging is performed at the “RAO” position and at the “LAO” position, respectively. Also, the number after “RAO” or “LAO” indicates the first rotation angle  25  (see  FIG. 7A  and  FIG. 7B ). Further, “CRA” and “CAU” indicate that imaging is performed at the CRANIAL position and at the CAUDAL position, respectively. The numbers after “CRA” and “CAU” indicate the second rotation angle  26  (see  FIG. 8A  and  FIG. 8B ). “HOME” indicates that the relative position of the imaging unit  2  with respect to the bed  1  is a HOME position (see  FIG. 2 ). The “01:RAO40, CRA20(HOME)” displayed on the display unit  8  indicates that “the first target position  40  is that the arm  23  is rotated at the RAO position of a rotation angle of 40 degrees and at the CRANIAL position of the rotation angle of 20 degrees, and the relative position of the imaging unit  2  with respect to the bed  1  is a HOME position.” 
     Note that the number of target positions  40  is two or more. In  FIG. 6 , four positions  40 , i.e., the first to fourth four target positions  40 , are displayed, but the fifth and subsequent target positions  40  can be displayed by scrolling. 
     As shown in  FIG. 7A , in a case where the target position  40  (see  FIG. 1 ) is a RAO position, the control unit  4  controls the rotation mechanism  61  so as to rotate the arm  23  in the Y 1 -direction from the position shown by the dotted line to the position shown by the solid line. Further, as shown in  FIG. 7B , in a case where the target position  40  is a LAO position, unlike the case of the RAO position, the control unit  4  controls the rotation mechanism  61  so as to rotate the arm  23  in the Y 2 -direction from the position shown by the dotted line to the position shown by the solid line. Note that the position shown by the dotted line is a position where the arm  23  is to be placed first and a combination of the front positions in  FIG. 2A  and  FIG. 2B . 
     As shown in  FIG. 8A , in a case where the target position  40  (see  FIG. 1 ) is a CRANIAL position, the control unit  4  controls the rotation mechanism  61  so as to rotate the arm  23  in the X 1 -direction from the position shown by the dotted line to the position shown by the solid line. Further, as shown in  FIG. 8B , in a case where the target position  40  is a CAUDAL position, unlike the case of the CRANIAL position, the control unit  4  controls the rotation mechanism  61  so as to rotate the arm  23  in the X 2 -direction from the position shown by the dotted line to the position shown by the solid line. Note that the position shown by the dotted line is a position where the arm  23  is to be arranged first and a combination of the front positions in  FIG. 2A  and  FIG. 2B . 
     The plurality of target positions  40  is set by the user in advance. For example, the control unit  4  makes the storage unit  3  store a plurality of target positions  40  and the order of imaging in an associated manner based on the operation input via the operation unit  5 . The control unit  4  may perform control to replace the order of imaging the plurality of target positions  40 , based on the operation input via the operation unit  5 , 
     Control In Sequence Mode 
     The control of the control unit  4  of the X-ray fluoroscopic imaging apparatus  100  of this embodiment in a sequence mode will be described with reference to  FIG. 9 . In Step  81 , the control unit  4  sets the first target position  40  among the plurality of target positions  40  stored in the storage unit  3  as a position toward which the imaging unit  2  is moved. 
     In Step  82 , an operation for moving the imaging unit  2  toward the target position  40  is received via the first operation unit  51 . Thus, the control unit  4  controls the rotation mechanism  61  and the moving mechanism  62  to move the imaging unit  2  toward the set target position  40 . At this time, at the position where an input of the movement operation has not become available anymore, the control unit  4  terminates the control to move the imaging unit  2  regardless of whether or not the imaging unit  2  has reached the target position  40 . Further, the control unit  4  receives an operation to move the imaging unit  2  in a direction different from a direction toward the target position  40  via the second operation unit  52 . This controls the rotation mechanism  61  or the moving mechanism  62  to move the imaging unit  2  in a direction different from the direction toward the target position  40 . As a result, the adjustment of the imaging position is performed. 
     In Step  83 , the control unit  4  determines by the first determination unit  41  whether or not imaging has been performed. In a case where it is determined that imaging has been performed, the process proceeds to Step  84 . In a case where it is determined that imaging has not been performed, the processing returns to Step  82 . 
     In Step  84 , the next Step changes depending on whether or not the next target position  40  has been stored in the storage unit  3 . In a case where the next target position  40  has been stored in the storage unit  3 , the process proceeds to Step  85  because the imaging of the subject  50  at the current target position  40  has been completed. In Step  85 , the control unit  4  switches the next target position  40  as a position toward which the imaging unit  2  is moved. Then, the process returns to Step  82 , and the processing from Step  82  to Step  85  is repeated. 
     In Step  84 , in a case where the next target position  40  has not been stored in the storage unit  3 , the control unit  4  terminates the sequence mode. 
     With reference to  FIG. 10 , the control to move the imaging unit  2  will be described in detail. In Step  91 , the next Step changes depending on whether or not there is either the input of the movement operation of the operation unit  51  via the first imaging unit  2  or the input of the movement operation of the imaging unit  2  via the second operation unit  52 . In a case where there is either the input of the movement operation of the imaging unit  2  via the first operation unit  51  or the input of the movement operation of the imaging unit  2  via the second operation unit  52 , the process proceeds to Step  92 . In Step  92 , the control unit  4  controls the rotation mechanism  61  and the moving mechanism  62  to move the imaging unit  2 . In a case where there is neither the input of the movement operation of the imaging unit  2  via the first operation unit  51  nor the input of the movement operation of the imaging unit  2  via the second operation unit  52 , the process proceeds to Step  94 . In Step  94 , the control unit  4  terminates the control to move the imaging unit  2 . 
     In Step  93 , the next Step changes depending on whether or not the input of the movement operation of the imaging unit  2  via the first operation unit  51  and the input of the movement operation of the imaging unit  2  via the second operation unit  52  have been terminated. In a case where the input of the movement operation of the imaging unit  2  via the first operation unit  51  and the input of the movement operation of the imaging unit  2  via the second operation unit  52  have been terminated (in a case where there is neither of inputs), the process proceeds to Step  94 . In Step  94 , the control unit  4  terminates the control to move the imaging unit  2 . In this case, regardless of whether or not the imaging unit  2  has reached the target position  40 , the control unit  4  terminates the control to move the imaging unit  2 . Then, the process proceeds to Step  95 . Also, in a case where either the input of the movement operation of the imaging unit  2  via the first operation unit  51  or the input of the movement operation of the imaging unit  2  via the second operation unit  52  is being received, the process proceeds to Step  92 . In Step  92 , the control unit  4  performs control to move the imaging unit  2 . Then, in Step  93 , the control unit  4  controls the rotation mechanism  61  and the moving mechanism  62  to move the imaging unit  2  until the input of the movement operation via the first operation unit  51  or the second operation unit  52  of the movement operation via the second operation unit  52  has been completed. That is, the control unit  4  performs to control the rotation mechanism  61  and the moving mechanism  62  to move the imaging unit  2  while either the input of the movement operation via the first operation unit  51  or the input of the movement operation via the second operation unit  52  continues. 
     In Step  95 , the proceeding step differs depending on whether or not there is an input operation to start imaging. In a case where there is an operation input to start imaging, the control unit  4  controls the rotation mechanism  61  and the moving mechanism  62  to terminate the control to move the imaging unit  2 . In a case where there is no operation input to start imaging, the process returns to Step  91 . The processing from Step  91  to Step  94  is repeated until there is an operation input to start imaging. Note that it is configured such that an operation input by the first operation unit  51  is not accepted at the time when the imaging unit  2  has reached the target position  40  during Step  94  from Step  91 , but the operation via the second operation unit  52  is accepted. That is, it is configured to determine whether or not there is an input of the moving operation of the imaging unit  2  via the second operation unit  52  after reaching the target position. 
     Effects of This Embodiment 
     In this embodiment, the following effects can be obtained. 
     In the X-ray fluoroscopic imaging apparatus  100  of the present invention, as described above, the apparatus is provided with the bed  1 , the imaging unit  2 , the storage unit  3 , the control unit  4 , and the drive unit  6 . The bed  1  is configured to place a subject  50  thereon. The imaging unit  2  includes the X-ray source  21  for irradiating the subject  50  with X-rays, the detector  22  for detecting X-rays emitted from the X-ray source  21 , the detector being arranged to face the X-ray source, and the arm  23  for connecting the X-ray source  21  and the detector  22 . The storage unit  3  stores a plurality of target positions  40  as targets toward which the imaging unit  2  is moved and the order of moving the imaging unit  2  toward the plurality of target positions  40  in an associated manner. The control unit  4  sequentially selects the plurality of target positions  40  in order. The drive unit  6  moves the imaging unit  2  toward the target position  40  switched by the control unit  4 . The control unit  4  includes a first determination unit  41  for determining whether or not X-ray imaging has been performed. The control unit  4  is configured to perform control to switch the target position to the next target position when it is determined by the first determination unit  41  that X-ray imaging has been performed. 
     With this, in a case where it is determined by the first determination unit  41  that X-ray imaging has been performed, the control unit  4  completes imaging regardless of the position of the imaging unit  2  after moving when the control to switch the target position to the next target position has been completed. With this, since the control unit  4  performs control to switch the target position  40 , it is possible to switch the target position  40  even in a case where imaging has been performed at a position other than the target position  40 . Consequently, in a case where imaging has been performed at any imaging position, it is possible to switch the target position to the next target position  40  without selecting the next target position  40 . 
     Further, in the above-described embodiment, the following further effects can be obtained by the following configuration. 
     That is, this embodiment is further provided with the position information acquisition unit  7  for acquiring the current information on the imaging unit  2  as described above. The control unit  4  includes the second determination unit  42  for determining whether or not the current position information of the imaging unit  2  acquired by the position information acquisition unit  7  matches the currently selected target position  40 . When it is determined by the first determination unit  41  that X-ray imaging has been performed, the control unit  4  is configured to perform control to switch the target position to the next target position even when it is determined by the second determination unit  42  that the current position information of the imaging unit  2  does not match the currently selected target position  40 , in addition to the case where it is determined by the second determination unit  42  that the current position information of the imaging unit  2  matches the currently selected target position  40 . As a result, in a case where it is determined by the first determination unit  41  that X-ray imaging has been performed, the control unit  4  is configured to perform the control to switch the target position to the next target position even in a case where it is determined by the second determination unit  42  that the current position information of the imaging unit  2  does not match the currently selected target position  40 , in addition to the case where it is determined by the second determination unit  42  that the current position information of the imaging unit  2  matches the currently selected target position  40 . With this configuration, even in a case where imaging has been performed at a position different from the target position  40 , the control unit  4  can switch the target position  40 . As a result, it is possible to perform a series of imaging of the subject  50  while arbitrarily selecting the imaging position without performing an operation for switching the target position  40 . 
     Further, in this embodiment, as described above, it is further provided with the operation unit  5  for receiving an operation for moving the imaging unit  2  toward the target position  40  and an operation for moving the imaging unit  2  in a direction different from a direction toward the target position  40 . The control unit  4  performs control to move the imaging unit  2  toward the target position  40  stored in the storage unit  3  when the operation for moving the imaging unit  2  toward the target position  40  is received. Further, the control unit  4  performs control to move the imaging unit  2  in a direction different from a direction toward the target position  40  when the operation for moving the imaging unit  2  in a direction different from a direction toward the target position  40  is received. In a case where it is determined by the first determination unit  41  that X-ray imaging has been performed, the control unit  4  is configured to perform the control to sequentially switch the plurality of target positions  40  after completing the imaging. This allows the user to move the imaging unit  2  along the path toward the target position  40  and move the imaging unit  2  to a position deviating from the path toward the target position  40 . Further, the control unit  4  is configured to perform control to sequentially switch the plurality of target positions  40  after completing the imaging even if the imaging unit  2  after moving has not yet reached the target position  40 . Therefore, the control unit  4  can switch the target position  40  even in a case where the user has performed imaging at a position deviating from the path toward the target position  40  in addition to the case where the user has performed imaging on the path toward the target position  40 . As a result, a series of imaging can be performed while adjusting the position at which the user performs imaging in accordance with the subject  50 . 
     First Modification of this Embodiment 
     With reference to  FIG. 1  to  FIG. 8 ,  FIG. 10 , and  FIG. 11 , a first modification of this embodiment will be described. Note that the same components as those of the above-described embodiment are allotted by the same reference numerals, and the descriptions thereof will be omitted. 
     The first modification differs from the first embodiment as follows. In a case where the difference between the position of the imaging unit  2  at the end of imaging and the target position  40  toward which the imaging unit  2  is moved to perform imaging is within a preset range, the control unit  4  controls as follows. That is, even in a case where the imaging unit  2  after moving has not yet reached the target position  40 , which is a case where it is determined by the second determination unit  42  that the current position of the imaging unit  2  does not match the target position  40 , the control unit  4  performs control to sequentially switch the plurality of target positions  40  after completing the imaging. Further, in a case where the difference between the position of the imaging unit after completing the imaging and the target position  40  toward which the imaging unit  2  is moved to perform imaging is outside a preset range, the control unit  4  performs control not to switch the target position  40 . The first modification is designed to prevent the target position from being switched due to the imaging unintended by the user, for example, when the same part has been imaged by mistake. 
     As shown in  FIG. 11 , in the first modification, the range of the difference between the position of the imaging unit  2  at the end of imaging, which is a condition for switching the target position  40 , and the target position  40  toward which the imaging unit  2  is moved to perform imaging is set. The range of the difference between the position of the imaging unit  2  at the end of imaging, which is a condition for switching the target position  40 , and the target position  40  toward which the imaging unit  2  is moved to perform imaging is stored in the storage unit  3 . The difference between the position of the imaging unit  2  at the end of imaging and the target position  40  toward which the imaging unit  2  is moved to perform imaging is a difference between the first rotation angles  25  (see  FIG. 7A  and  FIG. 7B ) and between the second rotation angles  26  (see  FIG. 8A  and  FIG. 8B ). The set range is the allowable range of the error between the first rotation angle  25  set to the current first rotation angle  40  and the first rotation angle at the position where the imaging was performed and the allowable range of the error between the second rotation angle  26  and the second rotation angle  26  at the position where the imaging was performed. The allowable range of the error is set, for example, within ±5 degrees or less. That is. in a case where the target position  40  is in the LAO40 position and the error is set to ±5 degrees, when the imaging position is positioned within a range from the LAO35 degrees to the LAO45 degrees, the control unit  4  performs control to switch the target position  40 . 
     In a case where the difference between the position of the imaging unit  2  at the end of imaging and the target position  40  toward which the imaging unit  2  is moved to perform imaging is outside the preset range, the control unit  4  terminates the sequence mode. The control unit  4  does not switch the target position  40  even if an operation input for imaging via the third operation unit  53  is performed. Note that, in this case, the control unit  4  starts the sequence mode from the received target position  40  by receiving the selection of the new target position  40 . The selection of the new target position  40  is performed by selecting one of the plurality of target positions  40  displayed on the display unit  8 . At this time, the next target position  40  of the current target position  40  may be selected, and another target position  40  may be selected. 
     With reference to  FIG. 11 , the control of the control unit  4  in the sequence mode of the first modification will be described. First, the control from Step  81  to Step  85  is the same as that of this embodiment. Further, the movement of the imaging unit  2  in Step  82  is the same control as in  FIG. 9 . Unlike the above-described embodiment, in this first modification, Step  86  is performed after imaging is completed in Step  83  and before the process proceeds to Step  84 . In Step  86 , the following step changes depending on whether or not the difference between the position at the end of imaging and the target position  40  toward which the imaging unit  2  is moved is within the preset value. 
     In a case where the difference between the position of the imaging unit  2  at the end of imaging and the target position  40  toward which the imaging unit  2  is moved to perform imaging is within the preset range, the process proceeds to Step  84 . In a case where the difference between the position at the end of imaging and the target position  40  toward which the imaging unit  2  is moved is outside the preset range, the process proceeds to Step  82 . 
     The rest of the configurations of the first modification is the same as those of the above-described embodiment. 
     Effects of First Modified Example 
     In the first modification, as described above, the bed  1 , the imaging unit  2 , the storage unit  3 , the control unit  4 , and the drive unit  6  are provided. The bed  1  is configured to lay a subject  50  thereon. The imaging unit  2  includes the X-ray source  21  for irradiating the subject  50  with X-rays, the detector  22  for detecting X-rays emitted from the X-ray source  21 , the detector  22  facing the X-ray source, and the arm  23  for connecting the X-ray source  21  and the detector  22 . The storage unit  3  stores the plurality of target positions  40  serving as targets toward which the imaging unit  2  is moved and the order of moving the imaging unit  2  toward the target positions  40  in an associated manner. The control unit  4  sequentially selects the plurality of target positions  40  in order. The drive unit  6  moves the imaging unit  2  toward the target position  40  switched by the control unit  4 . The control unit  4  includes the first determination unit  41  for determining whether or not X-ray imaging has been performed and is configured to perform control to switch the target position to the next target position when it is determined by the first determination unit  41  that X-ray imaging has been performed. 
     With this, when it is determined by the first determination unit  41  that X-ray imaging has been performed, the control unit  4  performs control to switch the target position to the next target position  40 . With this configuration, the control unit  4  performs control to switch the target position  40  upon completion of imaging regardless of the position of the imaging unit  2  after moving. Therefore, the target position  40  can be switched even in a case where imaging has been performed at a position other than the target position  40 . Consequently, in a case where imaging has been performed at any imaging position, it is possible to switch the target position to the next target position  40  without selecting the next target position  40 . 
     Further, in the above-described first modification, the following further effects can be obtained by the following configuration. 
     In the first modification, as described above, in a case where it is determined ty the second determination unit  42  that the current position information of the imaging unit  2  does not match the currently selected target position  40 , when the difference between the position of the imaging unit  2  at the end of imaging and the target position  40  toward which the imaging unit  2  is moved to perform imaging is within the preset range, the control unit  4  is configured to perform the following control. That is, the control unit  4  is configured to perform control to sequentially switch the plurality of target positions  40  after completion of the imaging even in a case where the imaging unit  2  after moving has not reached the target position  40 . Further, the control unit  4  is configured to perform control not to switch the target position  40  in a case where the difference between the position of the imaging unit at the end of imaging and the target position  40  toward which the imaging unit  2  is moved to perform imaging is outside the preset range. Thus, for example, in a case where a plurality of imaging operations is performed at the same position, e.g., when imaging is performed again, by setting a value smaller than the difference between consecutive target positions  40  as the upper limit of the preset range, after switching to the next target position  40  in the first imaging, the second and subsequent imaging positions are not the switched target position  40  but the preceding target position  40 . Therefore, the difference between the position of the imaging unit  2  at the end of the imaging and the target position  40  toward which the imaging unit  2  is moved to perform imaging is the difference between the consecutive target positions  40 . Then, the difference between the position of the imaging unit  2  at the end of imaging and the target position  40  toward which the imaging unit  2  is moved to perform imaging becomes larger than the preset range. Therefore, the control unit  4  performs control not to switch the target position  40 . As a result, it is possible to suppress the target position  40  from being sequentially switched every time imaging is performed at the same position. 
     Further, in the first modification, as described above, the arm  23  of the imaging unit  2  has an arc-shaped shape. The difference between the position of the imaging unit  2  at the end of imaging and the target position  40  toward which the imaging unit  2  is moved to perform imaging is the difference between the first rotation angles  25  at which the arm  23  of the imaging unit  2  rotates about a line extending in the longitudinal direction of the bed  1  connecting the head and the foot of the subject  50 , and the difference between the second rotation angles  26  at which the arm  23  of the imaging unit  2  rotates in the circumferential direction of the arm  23  of the imaging unit  2 . Here, in a case where the difference between at least either the first rotation angles  25  or the second rotation angles  26  is increased, there is a possibility that the position of the imaging unit  2  may largely deviate from the target position  40 . Therefore, in a case where the difference between the first rotation angles  25  and the second rotation angles  26  between the second rotation angle and the target position  40  toward which the imaging unit  2  is moved to perform imaging is outside the range, the control unit  4  performs control not to switch the target position  40 . With this, it is possible to suppress the target position  40  from being switched when imaging has been performed at a position largely deviating from the target position  40 . 
     Further, in the first modification, as described above, in a case where the difference between the position of the imaging unit  2  at the end of imaging and the target position  40  toward which the imaging unit  2  is moved is outside the preset range and the control not to switch the target position  40  is performed, the control unit  4  is configured to perform control to switch the plurality of target positions  40  upon receipt of the operation input for performing control to switch to the target position  40 . With this, in a case where the control unit  4  performs control not to switch the target position  40 , the user can switch the target position  40  by performing the control to switch the target position to any target position  40 . Consequently, the imaging can be started at any target position  40 . 
     The other effects of the first modification are the same as those of the above-described embodiment. 
     Second Modification of This Embodiment 
     A second modification will be described with reference to  FIG. 1  to  FIG. 10  and  FIG. 12 . The same configuration as the above-described embodiment will be omitted using the same reference numerals. 
     Unlike the above-described embodiment, the second modification  3  is configured such that the storage unit  3  collectively stores target positions  40  of a plurality of sites. Note that the rest of the configurations of the second modification is the same as those of the above-described embodiment. Therefore, the same reference numerals are allotted, and the descriptions thereof will be omitted. The plurality of imaging positions is, for example, a combination of a blood vessel of a heart and a blood vessel of a lower limb. 
     As shown in  FIG. 12 , the setting of the target positions  40  is performed for each site. For example, in a case where imaging is performed twice at each side, a target position  40  relating to the imaging of the first side as the first target position  40  and the second target position  40  is set. Further, a target position  40  relating to imaging of the second part as the third target position  40  and the fourth target position  40  is set. These are stored together in the storage unit  3 . 
     The following description will be directed to the case in which the sites to be imaged are a blood vessel of a heart and a blood vessel of a lower limb. In this case, since the position of the blood vessel of the heart and the position of the blood vessel of the lower limb are separated from each other, it is necessary to change the relative position of the imaging unit  2  with respect to the bed  1  after imaging the position of the blood vessel of the heart. For example, after imaging the blood vessel of the heart at a HOME position, the control unit  4  controls the moving mechanism  62  to move the imaging unit  2  to a PERI position in order to image the blood vessel of the lower limb. Therefore, the setting of the target position  40  is set so as to include the moving of the relative position toward which the arm  23  is moved to perform imaging from the HOME position to the PERI position. For example, the target position  40  is set for the first and second imaging of the blood vessel of the heart, the relative position of the imaging unit  2  after moving to the bed  1  is set for the third imaging, and the relative position  40  for the imaging unit  2  after changing to the bed  1  is for the fourth imaging, and the relative position  40  of the imaging unit  2  after changing to the bed  1  is set for the fourth and fifth imaging. In  FIG. 12 , “POSITIONING CHANGE” indicates the change of the relative position of arm  23  with respect to the bed  1 . Also, “PERI” after “POSITIONING CHANGE” indicates that the relative position after changing denotes the PERI position. The rest of the configurations of the second modification is the same as those of the above-described embodiment. 
     Effects of Second Modification 
     In the second modification, as described above, the bed  1 , the imaging unit  2 , the storage unit  3 , the control unit  4 , and the drive unit  6  are provided. The bed  1  is configured to lay a subject  50  thereon. The imaging unit  2  includes the X-ray source  21  for irradiating the subject  50  with X-rays, the detector  22  arranged to face the X-ray source  21  for the purpose of detecting the X-rays emitted from the X-ray source  21 , and the arm  23  for connecting the X-ray source  21  and the detector  22 . The storage unit  3  stores a plurality of target positions  40  serving as targets toward which the imaging unit  2  is moved to perform imaging and the order of moving the imaging unit  2  toward the plurality of target positions  40 . The control unit  4  sequentially selects the plurality of target positions  40  in order. The drive unit  6  moves the imaging unit  2  toward the target position  40  switched by the control unit  4 . The control unit  4  includes the first determination unit  41  for determining whether or not X-ray imaging has been performed. When it is determined by the first determination unit  41  that X-ray imaging has been performed, the control unit is configured to perform control to switch the target position to the next target position  40 . 
     Thus, in a case where it is determined by the first determination unit  41  that X-ray imaging has been performed, the control unit  4  performs control to switch the target position to the next target position  40 . Thus, the control unit  4  performs control to switch the target position  40  when the imaging has been completed regardless of the position of the imaging unit  2  after moving. Therefore, the target position  40  can be switched even in a case where imaging has been performed at a position other than the target position  40 . Consequently, in a case where imaging has been performed at an arbitrary imaging position, it is possible to switch to the target position to the next target position  40  without selecting the next target position  40 . 
     Further, in the above-described second modification, the following further effects can be obtained. 
     In the second modification, it is configured such that the target positions  40  of a plurality of sites are collectively stored in the storage unit  3 . As a result, since the target positions  40  of the plurality of sites are configured to be collectively stored in the storage unit  3 , there is no need to set the target position  40  for each target site. Therefore, it is possible to reduce the burden on the user who sets the target position  40 . 
     The other effects of the second modification are the same as those of the above-described embodiment. 
     Modified Embodiments 
     It should be understood that the embodiments disclosed here are examples in all respects and are not restrictive. The scope of the present invention is shown by claims rather than the descriptions of the embodiments described above, and includes all changes (modifications) within the meaning of equivalent and the scope of claims. 
     For example, in the above-described embodiment and the above-described first modification, an example is shown in which the arm  23  is of a single-plane type, but the present invention is not limited to thereto. For example, it may be of a biplane type in which two arms  23  are provided. In this case, the target positions of each arm may be displayed side by side on the display unit. Further, the storage unit may collectively store the movements of each arm. 
     Further, in the above-described embodiment, first modification, and second modification, an example is shown in which the operation units  5  for receiving the operation for moving the imaging unit  2  toward the target position and the operation for moving the imaging unit  2  in a direction different from a direction toward the target position are different from each other, but the present invention is not limited thereto. For example, one operation unit may be configured to accept both the operations. 
     In the above-described embodiment, first modification, and second modification, an example is shown in which the display unit  8  is a touch panel for accepting an operation input, but the present invention is not limited thereto. For example, the display unit may be a display panel that does not accept the operation input. 
     In the above-described embodiment, first modification, and second modification, the operation unit  5  and the display unit  8  are provided on the side of the bed  1 , but the present invention is not limited thereto. For example, the operation unit and the display unit may each be provided away from the bed. 
     Further, in the above-described embodiment, first modification, and second modification, an example is shown in which the difference between the position of the imaging unit  2  at the end of imaging and the target position  40  toward which the imaging unit  2  is moved to perform imaging is a difference between the first rotation angles  25  and the difference between the second rotation angles, but the present invention is not limited thereto. For example, the difference between the position of the imaging unit at the end of imaging and the target position toward which the imaging unit is moved to perform imaging may be the difference of the position coordinates showing the relative position between the imaging unit and the position coordinate. 
     Further, in the above-described first modification, an example is shown in which the selection of the new target position  40  is accepted via the display unit  8 , but the present invention is not limited thereto. For example, the target position displayed on the display unit may be selected by operating the operation unit. 
     Further, in the second modification, an example is shown in which the relative position of the imaging unit  2  with respect to the bed  1  is changed because the plurality of sites is separated from each other, but the present invention is not limited thereto. For example, in a case where a plurality of sites, such as, e.g., a blood vessel of a heart and a blood vessel of a lung, is closely positioned, the change of the relative position may not be included in the target position because there is no need to change the relative position. 
     Although the second modification has been described as a modification of the above-described embodiment, the second modification may be provided with the configuration of the first modification. 
     Aspects 
     It will be understood by those skilled in the art that the above-described exemplary embodiments are concrete examples of the following aspects. 
     (Item 1) 
     An X-ray fluoroscopic imaging apparatus comprising: 
     a bed configured to place a subject thereon; 
     an imaging unit including an X-ray source for irradiating the subject with X-rays, a detector for detecting X-rays emitted from the X-ray source, the detector facing the X-ray source, and an arm for connecting the X-ray source and the detector; 
     a storage unit configured to store a plurality of target positions serving as targets toward which the imaging unit is moved and an order of moving the imaging unit to the plurality of target positions in an associated manner; 
     a control unit configured to sequentially switch the plurality of target positions according to the order; and 
     a drive unit configured to move the imaging unit toward a target position switched by the control unit, 
     wherein the control unit includes a first determination unit configured to determine whether or not X-ray imaging has been performed, and 
     wherein when it is determined by the first determination unit that X-ray imaging has been performed, the control unit is configured to perform control to switch the target position to a next target position. 
     (Item 2) 
     The X-ray fluoroscopic imaging apparatus as recited in the above-described Item 1, further comprising: 
     a position information acquisition unit configured to acquire current information on the imaging unit, 
     wherein the control unit further includes a second determination unit for determining whether or not the current position information on the imaging unit acquired by the position information acquisition unit matches a currently selected target position, and 
     wherein when it is determined by the first determination unit that X-ray imaging has been performed, even in a case where it is determined by the second determination that the current position information on the imaging unit does not match the currently selected target position, in addition to a case where it is determined by the second determination unit that the current position information on the imaging unit matches the currently selected target position, the control unit performs control to switch the target position to the next target position. 
     (Item 3) 
     The X-ray fluoroscopic imaging apparatus as recited in the above-described Item 1 or 2, further comprising: 
     an operation unit configured to receive an operation for moving the imaging unit toward the target position and an operation for moving the imaging unit in a direction different from a direction toward the target position, 
     wherein the control unit performs 
     control to move the imaging unit toward the target position stored in the storage unit when an operation for moving the imaging unit toward the target position is received, 
     control to move the imaging unit in a direction different from a direction toward the target position when an operation for moving the imaging unit in the direction different from the direction toward the target position, and 
     a control to sequentially switch the plurality of target positions after completion of the imaging in a case where it is determined by the first determination unit that the X-ray imaging has been performed. 
     (Item 4) 
     The X-ray fluoroscopic imaging apparatus as recited in the above-described Item 2, 
     wherein in a case where it is determined by the second determination unit that the current position information on the imaging unit does not match the currently selected target position, the control unit is configured to perform 
     control to sequentially switch the plurality of target positions after completion of imaging even when the imaging unit after moving has not yet reached the target position in a case where a difference between the position of the imaging unit at an end of imaging and the target position toward which the imaging unit is moved to perform imaging is within a preset range, and 
     control not to switch the target position in a case where the difference between the position of the imaging unit after imaging and the target position toward which the imaging unit is moved to perform imaging is outside the preset range. 
     (Item 5) 
     The X-ray fluoroscopic imaging apparatus as recited in the above-described Item 4, 
     wherein the arm of the imaging unit has an arc-shaped shape, and 
     wherein the difference between the position of the imaging unit at the end of imaging and the target position toward which the imaging unit is moved to perform imaging is a difference between first rotation angles at which the arm of the imaging unit rotates about a line extending in a longitudinal direction of the bed connecting a head and a foot of the subject and a difference between second rotation angles at which the arm of the imaging unit rotates in a circumferential direction of the arm of the imaging unit. 
     (Item 6) 
     The X-ray fluoroscopic imaging apparatus as recited in the above-described Item 4 or 5, 
     wherein the control unit is configured to perform control to switch the plurality of target positions upon receipt of an operation input for selecting the target position. 
     (Item 7) 
     An X-ray fluoroscopic imaging method for an X-ray fluoroscopic imaging apparatus, the X-ray fluoroscopic imaging apparatus comprising an imaging unit for imaging a subject, and a plurality of target positions serving as targets toward which the imaging unit is performed and an order of moving the imaging unit toward the plurality of target positions being stored in an associated manner, 
     the X-ray fluoroscopic imaging method comprising the steps of: 
     determining whether or not X-ray imaging has been performed by the imaging unit; and 
     switching the target position to a next target position when it is determined that X-ray imaging has been performed.