X-ray fluoroscopic imaging apparatus

Abstract

To shorten stand-by time for filament heating when changing to imaging from fluoroscopy.SOLUTION: An X-ray tube includes: a first filament of which electron beam has a small focus size; and a second filament of which focus size is larger than that of the first filament. A controller sets heating time of the filament depending on whether a filament current is supplied in a fluoroscopic mode or an imaging mode before the imaging mode for this time when executing an imaging mode.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an X-ray fluoroscopic imaging apparatus capable of fluoroscopy and imaging. [Background technology]

[0002] An X-ray fluoroscopic imaging device is a device that performs fluoroscopy (moving image display) by irradiating a subject with a relatively small dose of X-rays and generating and displaying images of multiple frames per second (e.g., 30 frames / s).In addition, at a timing desired by the operator, the fluoroscopy can be stopped and a predetermined dose of X-rays larger than the fluoroscopy can be irradiated to the subject to capture one X-ray image (still image).

[0003] X-ray tubes used in X-ray fluoroscopy imaging devices generally have two types of filaments: a small focus filament with a small focus size suitable for irradiating a small dose of X-rays, and a large focus filament with a large focus size suitable for irradiating a large dose of X-rays, as disclosed in Patent Document 1. Small focus filaments are mainly used for fluoroscopy, and large focus filaments are mainly used for photography.

[0004] The operator decides the location to be photographed while viewing the fluoroscopic image, and switches from fluoroscopy to photography. At the stage when an instruction to switch to photography is given, the large focus filament is not yet heated, and it takes 1 to 2 seconds for the large focus filament to reach a temperature at which it can emit thermoelectrons. For this reason, conventional X-ray fluoroscopic imaging devices are configured to give instructions to photograph in two stages, in which the operator's first instruction starts overheating the large focus filament, and the operator is permitted to give an instruction for the second stage once 1 to 2 seconds have passed until the appropriate temperature has been reached.

[0005] In response to this, Patent Document 1 proposes an X-ray tube in which both the small focus filament and the large focus filament are constantly heated so that the operator does not have to wait 1 to 2 seconds when switching from fluoroscopy to radiography. By constantly heating two types of filaments, electron beams are constantly generated from the two types of filaments, but a grid is placed between the filament and the anode, and only one of the electron beams reaches the anode to generate X-rays. As a result, during fluoroscopy, the electron beam from the large focus filament does not reach the anode, and at the time of switching from fluoroscopy to radiography, the grid is controlled to make the electron beam from the large focus filament reach the anode, so that radiography can be performed by irradiating a large dose of X-rays without making the operator wait 1 to 2 seconds. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 5-258893 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, conventional X-ray tubes equipped with a small focus filament and a large focus filament make the operator wait for 1 to 2 seconds when switching from fluoroscopy to radiography, which causes stress for the operator.

[0008] On the other hand, the technology of Patent Document 1 has a problem in that the lifespan of the filaments is shortened because two types of filaments are constantly heated.

[0009] An object of the present invention is to shorten the waiting time for filament heating when switching from fluoroscopy to radiography. [Means for solving the problem]

[0010] In order to achieve the above object, the present invention provides an X-ray fluoroscopic imaging device having an X-ray tube for irradiating an object with X-rays, a voltage device connected to the X-ray tube, a control unit for controlling the voltage device, an X-ray detector for detecting X-rays transmitted through the object, and an operation unit. The X-ray tube includes an anode and a filament for irradiating an electron beam to the anode. The filament includes a first filament having a small focal spot size of the electron beam and a second filament having a larger focal spot size than the first filament. The voltage device selectively supplies a filament current to one of the first filament and the second filament, and applies a tube voltage between the filament and the anode. The control unit has a fluoroscopy mode and an imaging mode. In the fluoroscopy mode, when the control unit receives a fluoroscopy instruction from the operation unit, the control unit supplies a filament current to one of the first filament and the second filament, and applies a tube voltage to cause the anode to emit a small dose of X-rays. In the radiography mode, when an instruction to perform imaging is received from the operation unit, a filament current larger than that in the fluoroscopy mode is started to be supplied to one of the first and second filaments, and then, after a predetermined waiting time has elapsed, a tube voltage larger than that in the fluoroscopy mode is applied to emit a large dose of X-rays from the anode. When executing the radiography mode, the control unit sets the length of the waiting time to the filament to be used in the radiography mode out of the first and second filaments, depending on whether a filament current was supplied to the filament before the radiography mode to be executed this time. Effect of the Invention

[0011] According to the present invention, when switching from fluoroscopy to radiography, the waiting time for heating the filament can be shortened, and the waiting time of the operator can be shortened. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram showing the overall configuration of an X-ray fluoroscopic imaging apparatus according to a first embodiment of the present invention. [Diagram 2] 1 is a block diagram showing the configuration of an X-ray high voltage device 100 of the X-ray fluoroscopic imaging apparatus of the first embodiment. [Diagram 3]2 is a circuit diagram showing the configuration of an X-ray tube device 7 of the X-ray fluoroscopic imaging apparatus of the embodiment 1. [Figure 4] 5 is a flowchart showing the operation of a control unit 8 of the X-ray fluoroscopic imaging apparatus of the first embodiment. [Diagram 5] 10 is a flowchart showing the operation of a control unit 8 of the X-ray fluoroscopic imaging apparatus of the second embodiment. [Figure 6] 11 is a flowchart showing the operation of a control unit 8 of the X-ray fluoroscopic imaging apparatus of the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an X-ray fluoroscopic imaging apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[0014] <<Embodiment 1>> An explanation will be given of an X-ray fluoroscopic imaging apparatus according to embodiment 1. Fig. 1 is a diagram showing the overall configuration of the X-ray fluoroscopic imaging apparatus, Fig. 2 is a diagram showing the configuration of an X-ray high voltage device 100, Fig. 3 is a diagram showing the configuration of an X-ray tube device 7, and Fig. 4 is a flowchart showing the operation of a control unit 8.

[0015] 1, the X-ray fluoroscopic imaging apparatus of the first embodiment includes an X-ray tube device 7 that irradiates a subject with X-rays, an X-ray high voltage device 100 connected to the X-ray tube device 7, a control unit 8 built in the X-ray high voltage device 100, a fluoroscopic imaging table 220, an X-ray detector 210 arranged inside the fluoroscopic imaging table 220, and an operation console 300. The fluoroscopic imaging table 220 is provided with a top plate 200, and a subject is placed on the top plate 200. The X-ray detector 210 detects X-rays that have passed through the subject.

[0016] The operation console 300 includes an image processing device 310, an operation unit 320, and a display device 330. The image processing device 310 receives the output of the X-ray detector 210, generates fluoroscopic images and radiographic images, and displays them on the display device 330. The operation unit 320 includes a fluoroscopy switch 320a for instructing the start of fluoroscopy, an imaging switch 320b for instructing the start of imaging, and an input unit 320c through which the operator inputs imaging conditions and the like.

[0017] As shown in Fig. 2, the X-ray tube device 7 includes an X-ray tube 11 incorporating a filament 20 and an anode 10, and a stator 9 that rotates the anode 10. The filament 20 is heated by the supply of a filament current and emits thermoelectrons. These thermoelectrons become an electron beam due to a tube voltage applied between the filament 20 and the anode 10, and are irradiated onto the anode 10. As a result, a tube current flows between the anode 10 and the filament 20.

[0018] The filaments 20 include a first filament 21 having a small focal spot size on the anode 10 of the electron beam, and a second filament 22 having a larger focal spot size than the first filament 21. The first filament 21 having a small focal spot size is more suitable for irradiating a smaller dose of X-rays than the second filament 22 having a large focal spot size.

[0019] The X-ray high voltage device 100 selectively supplies a filament current to one of the first filament 21 and the second filament 22. The X-ray high voltage device 100 also applies a tube voltage between the filaments 21, 22 and the anode 10.

[0020] The X-ray high voltage device 100 is configured to include a rectifier circuit 2 that rectifies AC power from an external commercial AC power source 1, a boost chopper circuit 3 that boosts the rectified DC power, an inverter circuit / heating circuit 4 that generates AC power of a desired frequency from the boosted DC power and generates a filament current, and a high voltage generation circuit 5 that generates a desired high tube voltage from the AC power of the desired frequency output by the inverter circuit / heating circuit 4.

[0021] The control unit 8 has a fluoroscopy mode and an imaging mode. When the operator turns on the fluoroscopy switch 320a of the operation unit 320 and issues an instruction to perform fluoroscopy, the control unit 8 executes the fluoroscopy mode. That is, the control unit 8 supplies a filament current from the inverter circuit / heating circuit 4 and the high voltage generating circuit 5 to one of the first filament and the second filament, and applies a tube voltage between the anode 10 and the filament 20. As a result, the first filament and the second filament that have received the filament current are caused to irradiate the anode 10 with an electron beam, causing the anode 10 to emit a relatively small dose of X-rays.

[0022] The irradiated X-rays pass through the subject and are detected by the X-ray detector 210. The image processing device 310 generates images from the output of the X-ray detector 210 at a predetermined rate (e.g., 30 frames / s) and displays them on the display device 330. As a result, a fluoroscopic image (moving image) is displayed on the display device 330.

[0023] On the other hand, when the operator turns on the imaging switch 320b of the operation unit 320 and issues an instruction to perform imaging, the control unit 8 executes the imaging mode. That is, the control unit 8 starts supplying a filament current larger than that in the fluoroscopy mode to one of the first and second filaments from the inverter circuit / heating circuit 4 and the high voltage generating circuit 5, and when a predetermined waiting time has elapsed, applies a tube voltage larger than that in the fluoroscopy mode between the anode 10 and the filament 20. This causes the anode 10 to radiate a larger dose of X-rays than during fluoroscopy.

[0024] The irradiated X-rays pass through the subject and are detected by the X-ray detector 210. The image processing device 310 generates one image from the output of the X-ray detector 210, and displays it on the display device 330. As a result, the captured image is displayed on the display device 330.

[0025] In this embodiment, the control unit 8 sets the length of the standby time when executing the shooting mode. At this time, the control unit 8 sets the length of the standby time depending on whether or not a filament current was supplied from the inverter circuit / heating circuit 4 and the high voltage generating circuit 5 to the filament to be used in the shooting mode out of the first filament 21 and the second filament 22 before the shooting mode to be executed this time.

[0026] Specifically, when switching from the fluoroscopy mode to the imaging mode after executing the fluoroscopy mode, if one of the first filament 21 and the second filament 22, which is different from the filament used in the fluoroscopy mode, is used in the imaging mode, the control unit 8 sets a first waiting time determined in advance as the waiting time. If the same filament as that used in the fluoroscopy mode is used in the imaging mode, a second waiting time shorter than the first waiting time is set.

[0027] The operation of the control unit 8 will be described in further detail below with reference to the flow in Fig. 4. The flow in Fig. 4 is an operation in which fluoroscopy is first performed, and then switching to radiography during fluoroscopy is performed, and radiography is then performed.

[0028] The control unit 8 is configured by a computer or the like equipped with a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit) and a memory, and the CPU reads and executes a program stored in the memory (storage unit), thereby realizing the operations shown in the flow of Fig. 4. Note that the control unit 8 can also be configured in part or in whole by hardware. For example, a circuit can be designed to realize the operations of the flow of Fig. 4 using a custom IC such as an ASIC (Application Specific Integrated Circuit) or a programmable IC such as an FPGA (Field-Programmable Gate Array).

[0029] (Step 101) When the operator turns on the power supply of the device, or when the operator issues an instruction to start an examination by operating the input unit 320c, the control unit 8 accepts the operation and starts the rotation of the anode 10.

[0030] (Step 102) Next, when the operator presses the fluoroscopy switch 320a to instruct the start of fluoroscopy, the control unit 8 accepts this, supplies a predetermined filament current to the filament used for fluoroscopy (the first filament 21 for a small focus or the second filament 22 for a large focus), and applies a predetermined tube voltage between the anode 10 and the filament 20.

[0031] The filament 20 used during fluoroscopy is a predetermined filament (here, the first filament 21 for a small focus). However, the filament 20 to be used during fluoroscopy may be specified by the operator via the input unit 320c.

[0032] This generates a small dose of X-rays for fluoroscopy and irradiates the subject.

[0033] The X-ray detector 210 detects X-rays transmitted through the subject. The image processing device 310 receives output data from the X-ray detector 210, generates a fluoroscopic image at a predetermined frame rate (e.g., 30 frames / s), and displays the image on the display device 330.

[0034] (Step 103) The control unit 8 receives luminance information of the generated perspective image from the image processing device 310, and performs feedback control to increase the filament current and tube voltage if the luminance is lower than a predetermined value. (Step 104) The control unit 8 calculates the imaging conditions (selection of whether the filament used for imaging is the first filament 21 or the second filament 22, the filament current being supplied, and the tube voltage) when switching to imaging based on the fluoroscopy conditions (whether the filament used for imaging is the first filament 21 or the second filament 22, the filament current being supplied, and the tube voltage) by referring to tables and formulas that have been obtained in advance.

[0035] The fluoroscopy conditions (filament current, tube voltage) reflect the state of the subject (thickness and part of the subject) because they are feedback-controlled in step 103. Therefore, by determining the relationship between the fluoroscopy conditions and the imaging conditions in advance by experiment or calculation, and creating a table or formula, it is possible to calculate appropriate imaging conditions corresponding to the state of the subject.

[0036] (Steps 105 and 106) The control unit 8 repeats steps 103 and 104 and continues fluoroscopy until pressing of the imaging switch is received.

[0037] If pressing of the imaging switch is accepted, the process proceeds to step 106, where the supply of filament current to the filament for fluoroscopy and the supply of tube voltage between the anode 10 and the filament 20 are stopped, and fluoroscopy is terminated.

[0038] (Steps 107, 108, 109) Next, the control unit 8 determines whether the filament for imaging calculated (selected) in step 104 is the same as the filament used for fluoroscopy (step 107). If it is a different filament, the filament used for imaging is not heated at all, so the process proceeds to step 109, and a predetermined waiting time (heating time) is set (step 109).

[0039] This waiting time (heating time) is the time required for the temperature of the imaging filament to rise to a temperature at which an electron beam capable of emitting a large dose used for imaging can be emitted from the anode 10 when a filament current is supplied to the filament that has not been heated at all up until that point. This waiting time (heating time) is a time previously determined for each of the first filament 21 and the second filament 22. It is selected and set according to the same filament used for imaging calculated in step 104.

[0040] (Step 108) On the other hand, in step 106, when the filament for imaging calculated (selected) in step 104 is the same filament as the filament used for fluoroscopy, since a filament current is supplied during fluoroscopy and the filament is already heated to a certain degree, the time required to increase the temperature from this state to a state where a large dose used for imaging can be irradiated is shorter than the waiting time (heating time) in step 109. Therefore, the process proceeds to step 108, where the heating time is calculated and set.

[0041] Specifically, the control unit 8 calculates the difference between the filament current supplied to the filament during fluoroscopy, which was adjusted in step 103, and the filament current for radiography, which was calculated in step 104. According to the calculated difference, the control unit 8 calculates the heating time required to raise the temperature of the filament for radiography to a temperature at which a large dose can be irradiated, using a table or formula indicating the relationship between the difference and the required heating time, which has been calculated in advance by experiment or calculation.

[0042] In addition to the above difference, these tables and formulas may also include other parameters such as a filament current for imaging and an outside air temperature.

[0043] (Step 110) The control unit 8 starts supplying the filament current calculated in step 104 to the filament for imaging selected in step 104.

[0044] (Step 111) When the heating time (standby time) of the filament for imaging set in step 109 or 108 has elapsed, the control unit 8 determines that the temperature of the filament for imaging has risen to a temperature at which an electron beam can be irradiated to emit a large dose for imaging from the anode 10, and proceeds to step 112.

[0045] (Step 112) The control unit 8 applies a tube voltage between the imaging filament and the anode, and irradiates the anode with an electron beam from the imaging filament, thereby irradiating the anode with a large dose of X-rays for imaging.

[0046] The X-rays pass through the subject and are detected by the X-ray detector 210. The image processing device 310 generates an image (X-ray image) and displays it on the display device 330.

[0047] According to this embodiment, when the filament used for fluoroscopy and the filament used for radiography are the same, the waiting time for heating is shortened, and the waiting time of the operator is shortened. Therefore, the convenience of the operator is improved and the stress of the operator can be reduced.

[0048] <<Embodiment 2>> The X-ray fluoroscopic imaging apparatus of the second embodiment will be described with reference to the flow chart of Fig. 5. The device configuration of the X-ray fluoroscopic imaging apparatus of the second embodiment is similar to that of the first embodiment. In the flow chart of Fig. 5 of the second embodiment, the same operation steps as those in the flow chart of Fig. 4 of the first embodiment are denoted by the same numbers.

[0049] In embodiment 2, when different filaments are used for fluoroscopy and imaging, when executing the imaging mode, if filament current was supplied to the filament used in the imaging mode, either the first filament 21 or the second filament 22, in the imaging mode prior to the imaging mode being currently executed, the control unit 8 sets the standby time according to the length of the pause time during which no filament current was supplied from the previous imaging mode to the current imaging mode.

[0050] A specific operation of the control unit 8 will be described with reference to the flow chart of FIG.

[0051] (Step 101) Similar to the flow of FIG. 4 in the first embodiment, the control unit 8 starts the rotation of the anode 10.

[0052] (Step 202) When the operator presses the fluoroscopy switch 320a, the control unit 8 always selects the first filament 21 of the small focus size, which is different from the first embodiment. A predetermined filament current is supplied to the small focus filament, and a tube voltage is applied between the anode 10 and the filament 20.

[0053] (Steps 103-106) As in the first embodiment, fluoroscopy is performed, imaging conditions are calculated, and when the imaging switch 320b is pressed, the fluoroscopy ends.

[0054] (Steps 107, 209) In step 107, if the filament for imaging calculated (selected) in step 104 is the second filament of a large focal size, in step 209, the control unit 8 sets a waiting time according to the pause time counted in step 214 described later.

[0055] What is counted in step 214 is the time during which no current was supplied to the second filament 22 of the large focal spot size from the previous imaging mode to the current imaging mode. During the previous imaging, the filament current for imaging was supplied to the second filament 22, causing the temperature to rise, but the temperature gradually drops during the pause time. Therefore, if the pause time is short, the time required to heat the second filament 22 to a state where it can emit a large dose for imaging in the current imaging is short. However, if the pause time is long, the time required to heat the second filament 22 to a state where it can emit a large dose for imaging in the current imaging is long.

[0056] Therefore, in the second embodiment, in step 209, the heating time (standby time) is calculated and set according to the pause time counted in step 214 by referring to a table previously obtained by experiment or calculation.

[0057] (Steps 108, 110~112) In addition, when the filament for imaging calculated (selected) in step 104 is the second filament with a large focal size, in step 108, the control unit 8 calculates and sets the heating time based on the difference in filament current between fluoroscopy and imaging, as in embodiment 1.

[0058] Steps 110 to 112 are carried out in the same manner as in embodiment 1, and a filament current is started to flow to the second filament 22 of the large focal spot size. After the heating time (standby time) set in step 209 or 108 has elapsed, a tube voltage is applied and imaging is performed.

[0059] (Steps 213 and 214) The control unit 8 proceeds to step 213, and if the filament for imaging selected in step 104 is the second filament 22 of the large focal size, the control unit 8 proceeds to step 214 and counts the pause time until the next time the imaging switch 320b is pressed.

[0060] According to the second embodiment, in addition to the effects of the first embodiment, even if the filament used for fluoroscopy and the filament used for radiography are different, if the time elapsed since the previous radiography is short, the standby time (heating time) is shortened. Therefore, the convenience for the operator is further improved compared to the first embodiment.

[0061] <<Embodiment 3>> The X-ray fluoroscopic imaging apparatus of the third embodiment will be described with reference to the flow chart of Fig. 6. The device configuration of the X-ray fluoroscopic imaging apparatus of the third embodiment is similar to that of the first embodiment. In the flow chart of Fig. 6 of the third embodiment, the same operation steps as those in the flow chart of Fig. 4 of the first embodiment are denoted by the same numbers.

[0062] In the third embodiment, when executing the imaging mode, the control unit 8 receives information on the part of the subject to be imaged and the body thickness from the input unit 320c of the operation unit 320, and selects the filament to be used for imaging from the first filament 21 and the second filament 22. Then, the selected filament is also used for fluoroscopy.

[0063] As a result, when switching from fluoroscopy to radiography, the filament is not switched, and the time required to heat the filament for radiography is shortened.

[0064] (Steps 301 and 302) First, the control unit 8 receives a selection of an examination region (head, abdomen, leg, etc.) from the operator via the input unit 320c (step 301), and then receives an input of the body thickness of the examination region of the subject (step 302).

[0065] (Step 303) The control unit 8 selects the first filament 21 or the second filament 22 as a filament for imaging by referring to a predetermined table or formula based on the examination site and body thickness received in steps 301 and 302. In the table, a filament for imaging (either the first filament 21 with a small focal spot size or the second filament 22 with a large focal spot size) suitable for each combination of examination site and body thickness, which have been obtained in advance by experiment or calculation, is determined.

[0066] This allows the control unit 8 to select a filament for imaging that is suitable for the combination of the examination site and body thickness of the subject to be imaged.

[0067] (Step 101) Next, the control unit 8 proceeds to step 101, and similarly to the first embodiment, when an instruction to start the inspection is received from the operator, the control unit 8 starts rotating the anode 10. (Steps 304~306) The control unit selects the same filament for fluoroscopy as the filament for imaging selected in step 303.

[0068] Specifically, when the filament for imaging selected in step 303 is the first filament 21 with a small focal spot size (step 304), the first filament 21 with a small focal spot size is selected as the filament for fluoroscopy (step 305).

[0069] If the filament for imaging selected in step 303 is not the first filament 21 with a small focal size (step 304), the second filament 22 with a large focal size is selected as the filament for fluoroscopy (step 305).

[0070] (Steps 102 and 103) Next, similar to steps 102 and 103 in embodiment 1, when the operator presses the fluoroscopy switch 320a, the control unit 8 supplies a predetermined filament current to the filament for fluoroscopy selected in steps 304 to 306, applies a predetermined tube voltage between the anode 10 and the filament 20, and starts fluoroscopy.

[0071] Furthermore, the control unit 8 receives luminance information of the perspective image from the image processing device 310 and performs feedback control of the filament current and the tube voltage.

[0072] (Step 307) Next, the control unit 8 calculates the imaging conditions (filament current, tube voltage) when switched to imaging based on the fluoroscopy conditions (filament current, tube voltage) by referring to a table or formula obtained in advance, similar to step 104 in embodiment 1. However, unlike step 104 in embodiment 1, the filament used for imaging is determined to be the filament used for fluoroscopy, and therefore the filament used for imaging is not selected.

[0073] (Steps 105~106, 108, 110~112) Thereafter, the control unit performs steps 105-106, 108, and 110-112 of the first embodiment. That is, the control unit 8 continues fluoroscopy until it receives pressing of the imaging switch, and when it receives pressing of the imaging switch, it ends fluoroscopy and calculates and sets the heating time required to raise the temperature of the imaging filament, which is the same as that for fluoroscopy, to a temperature at which a large dose can be irradiated. It starts supplying the imaging filament with the filament current calculated in step 307, and when the heating time (standby time) set in step 108 has elapsed, it applies a tube voltage, irradiates a large dose of X-rays for imaging, and performs imaging.

[0074] According to this embodiment, the same filament is selected for fluoroscopy and radiography in advance according to the part of the subject and the body thickness, so the waiting time for heating is always short. This shortens the waiting time for the operator, improving the convenience for the operator. [Explanation of symbols]

[0075] 1 Commercial AC power supply 2 Rectifier circuit 3. Boost chopper circuit 4 Heating circuit 5 High voltage generation circuit 7 X-ray tube equipment 8. Control Unit 9 Stator 10 Anode 11 X-ray tube 20 Filaments 21 First filament 22 Second filament 100 X-ray high voltage device 200 Tabletop 210 X-ray detector 220 Fluoroscopy Table 300 Control console 310 Image Processing Device 320 Control unit 320a X-ray switch 320b Shooting switch 320c Input section 330 Display device

Claims

1. The apparatus includes an X-ray tube for irradiating an object with X-rays, a voltage device connected to the X-ray tube, a control unit for controlling the voltage device, an X-ray detector for detecting the X-rays transmitted through the object, and an operation unit, The X-ray tube includes an anode and a filament for irradiating an electron beam to the anode, the filament including a first filament having a small focal spot size of the electron beam and a second filament having a larger focal spot size than the first filament; the voltage device selectively supplies a filament current to one of the first filament and the second filament and applies a tube voltage between the filament and the anode; The control unit has a fluoroscopy mode and an imaging mode, the control unit, in the fluoroscopy mode, upon receiving a fluoroscopy instruction from the operation unit, supplies a filament current to one of the first filament and the second filament, applies a tube voltage, and causes the anode to radiate a small dose of X-rays; and in the radiography mode, upon receiving an image capturing instruction from the operation unit, supplies a filament current larger than that in the fluoroscopy mode to one of the first filament and the second filament, and after a predetermined waiting time has elapsed, applies a tube voltage larger than that in the fluoroscopy mode, and causes the anode to radiate a large dose of X-rays; The control unit, when executing the shooting mode, sets the length of the waiting time depending on whether a filament current was supplied to the filament to be used in the shooting mode, out of the first filament and the second filament, prior to the shooting mode being currently executed.

2. 2. The X-ray fluoroscopic imaging device according to claim 1, wherein the control unit, when switching from the fluoroscopy mode to the imaging mode after executing the fluoroscopy mode, sets a predetermined first waiting time as the waiting time when a filament different from the filament used in the fluoroscopy mode is used in the imaging mode among the first filament and the second filament, and sets a second waiting time shorter than the first waiting time when the same filament as the filament used in the fluoroscopy mode is used in the imaging mode.

3. 2. The X-ray fluoroscopy imaging device according to claim 1, wherein when executing the shooting mode, if a filament current has been supplied to one of the first filament and the second filament to be used in the shooting mode prior to the shooting mode being currently executed, the control unit sets the waiting time based on a difference between the filament current that was supplied and the filament current to be supplied in the shooting mode being currently executed.

4. 2. The X-ray fluoroscopy imaging device according to claim 1, wherein when executing the shooting mode, if a filament current has been supplied to one of the first filament and the second filament used in the shooting mode in a fluoroscopy mode prior to the shooting mode being currently executed, the control unit calculates a filament current for the shooting mode in accordance with the filament current for the fluoroscopy mode.

5. 2. The X-ray fluoroscopic imaging device according to claim 1, wherein when executing the shooting mode, if a filament current was supplied to one of the first filament and the second filament used in the shooting mode in the shooting mode prior to the shooting mode being currently executed, the control unit sets the waiting time according to a length of a pause time during which no filament current was supplied from the previous shooting mode to the current shooting mode.

6. 2. The X-ray fluoroscopic imaging device according to claim 1, wherein the control unit receives information on an imaging site of a subject from the operation unit, selects a filament to be used in the imaging mode from among the first filament and the second filament, and uses the selected filament also in the fluoroscopy mode.

7. 2. The X-ray fluoroscopy imaging device according to claim 1, wherein the control unit determines, by referring to a table obtained in advance, whether the filament used for fluoroscopy is the first filament or the second filament, the filament current, and one or more of the tube voltage when the fluoroscopy mode is switched to the imaging mode, based on one or more conditions of whether the filament used in the fluoroscopy mode is the first filament or the second filament, the filament current supplied to the filament in the fluoroscopy mode, and the tube voltage.

8. 2. The X-ray fluoroscopic imaging device according to claim 1, wherein the control unit feedback-controls at least one of a filament current and a tube voltage in accordance with a detection result of the X-ray detector while the fluoroscopy mode is being executed.

Images