X-ray fluoroscopic imaging device

Abstract

The present invention addresses the problem of providing an X-ray fluoroscopic imaging device that shortens the standby time for filament heating when switching from fluoroscopic to imaging. The X-ray tube includes a first filament having a small focus size of an electron beam and a second filament having a larger focus size than the first filament. When the imaging mode is executed, the control unit sets the length of the heating time of the filament according to whether the filament current is supplied in the perspective mode or the imaging mode before the current imaging mode.

Description

Technical Field

[0001] The present invention relates to an X-ray fluoroscopic imaging device capable of performing fluoroscopy and photography. Background Art

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

[0003] As disclosed in Patent Document 1, an X-ray tube used in an X-ray fluoroscopic imaging device generally has two types: a small focus filament having a small focus size suitable for irradiating a small dose of X-rays, and a large focus filament having a large focus size suitable for irradiating a large dose of X-rays. The small focus filament is mainly used for fluoroscopy, and the large focus filament is mainly used for imaging.

[0004] The operator determines the imaging part while observing the fluoroscopic image and switches from fluoroscopy to imaging. At the stage of switching to imaging, the large focus filament has not yet been heated, and it takes 1 to 2 seconds for the large focus filament to reach a temperature that can release thermal electrons. Therefore, the conventional X-ray fluoroscopic imaging device is configured to perform imaging instructions in two stages. The heating of the large focus filament starts under the operator's instruction of the first stage, and after 1 to 2 seconds until the appropriate temperature is reached, the operator is allowed to give the instruction of the second stage.

[0005] In contrast, Patent Document 1 proposes an X-ray tube that always heats both a small-focus filament and a large-focus filament in order to avoid making the operator wait for 1 to 2 seconds when switching from fluoroscopy to photography. By always heating both filaments, electron beams are always generated from both filaments, but a grid is arranged between the filaments and the anode so that only one type of electron beam 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 photography, the electron beam from the large-focus filament reaches the anode by controlling the grid, thereby making it possible to irradiate a large dose of X-rays for photography without making the operator wait for 1 to 2 seconds.

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 5-258893

[0007] As described above, since the conventional X-ray tube having a small-focus filament and a large-focus filament makes the operator wait for 1 to 2 seconds when switching from fluoroscopy to imaging, the operator feels stressed.

[0008] On the other hand, the technology of Patent Document 1 has a problem in that the life of the filaments is shortened because both filaments are heated at all times. Summary of the invention

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

[0010] In order to achieve the above-mentioned object, according to the present invention, there is provided an X-ray fluoroscopic imaging device, which comprises: 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 that have penetrated the object; and an operation unit. The X-ray tube comprises an anode and a filament for irradiating an electron beam to the anode. The filament comprises 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 while applying a tube voltage between the filament and the anode. The control unit has a fluoroscopic mode and a photographic mode. In the fluoroscopic mode, if the control unit receives a fluoroscopic instruction from the operation unit, the filament current is supplied to one of the first filament and the second filament while applying a tube voltage, so that a small dose of X-rays is radiated from the anode. In the photographing mode, when an instruction to photograph is received from the operation unit, after a filament current larger than that in the fluoroscopic mode is supplied to one of the first filament and the second filament, if a predetermined standby time has passed, a tube voltage larger than that in the fluoroscopic mode is applied to emit a large dose of X-rays from the anode. When the photographing mode is executed, the control unit sets the length of the standby time according to whether the filament current was supplied to the filament used in the photographing mode, of the first filament and the second filament, before the currently executed photographing mode.

[0011] Effects of the Invention

[0012] According to the present invention, when switching from fluoroscopy to imaging, the waiting time for heating the filament can be shortened, thereby shortening the waiting time of the operator. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a block diagram showing the overall configuration of the X-ray fluoroscopy apparatus according to the first embodiment of the present invention.

[0014] Figure 2 1 is a block diagram showing the configuration of an X-ray high voltage device 100 of the X-ray fluoroscopy device according to the first embodiment.

[0015] Figure 3 1 is a circuit diagram showing the configuration of the X-ray tube device 7 of the X-ray fluoroscopy apparatus according to the first embodiment.

[0016] Figure 4 This is a flowchart showing the operation of the control unit 8 of the X-ray fluoroscopy apparatus according to the first embodiment.

[0017] Figure 5 This is a flowchart showing the operation of the control unit 8 of the X-ray fluoroscopy apparatus according to the second embodiment.

[0018] Figure 6 This is a flowchart showing the operation of the control unit 8 of the X-ray fluoroscopy apparatus according to the third embodiment.

[0019] Explanation of symbols

[0020] 1-commercial AC power supply, 2-rectifier circuit, 3-boost chopper circuit, 4-inverter circuit / heating circuit, 5-high voltage generating circuit, 7-X-ray tube device, 8-control unit, 9-statator, 10-anode, 11-X-ray tube, 20-filament, 21-first filament, 22-second filament, 100-X-ray high voltage device, 200-top plate, 210-X-ray detector, 220-fluoroscopic photography table, 300-operating table, 310-image processing device, 320-operating unit, 320a-fluoroscopic switch, 320b-photographic switch, 320c-input unit, 330-display device. DETAILED DESCRIPTION

[0021] Hereinafter, an X-ray fluoroscopy imaging device according to an embodiment of the present invention will be described with reference to the drawings.

[0022] <<Implementation Method 1>>

[0023] The X-ray fluoroscopy imaging device according to the first embodiment will be described. Figure 1 is a diagram showing the overall structure of an X-ray fluoroscopic imaging device. Figure 2 is a diagram showing the structure of the X-ray high voltage device 100, Figure 3 is a diagram showing the structure of an X-ray tube device 7, Figure 4 It is a flowchart showing the operation of the control unit 8 .

[0024] like Figure 1 As shown, the X-ray fluoroscopy apparatus of the first embodiment includes: an X-ray tube device 7 for irradiating an object with X-rays; an X-ray high voltage device 100 connected to the X-ray tube device 7; a control unit 8 built into the X-ray high voltage device 100; a fluoroscopy table 220; an X-ray detector 210 disposed inside the fluoroscopy table 220; and an operation table 300. The fluoroscopy table 220 includes a top plate 200, and the object is placed on the top plate 200. The X-ray detector 210 detects X-rays that have penetrated the object.

[0025] The 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 a fluoroscopic image or a radiographic image, and displays it on the display device 330. The operation unit 320 includes a fluoroscopic switch 320a for instructing the start of fluoroscopy, a radiographic switch 320b for instructing the start of radiography, and an input unit 320c for the operator to input radiographic conditions and the like.

[0026] like Figure 2 As shown, the X-ray tube device 7 includes an X-ray tube 11 having a filament 20 and an anode 10 therein, and a stator 9 for rotating the anode 10. The filament 20 is heated by being supplied with a filament current, thereby releasing thermal electrons. The thermal electrons are converted into electron beams by a tube voltage applied between the filament 20 and the anode 10, and are irradiated to the anode 10. Thus, the tube current flows between the anode 10 and the filament 20.

[0027] The filaments 20 include a first filament 21 having a small focal spot size of the electron beam on the anode 10 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 suitable for irradiating a smaller dose of X-rays than the second filament 22 having a large focal spot size.

[0028] The X-ray high voltage device 100 selectively supplies a filament current to one of the first filament 21 and the second filament 22 . In addition, the X-ray high voltage device 100 applies a tube voltage between the filaments 21 and 22 and the anode 10 .

[0029] The X-ray high voltage device 100 is constructed to include: a rectifier circuit 2 for rectifying the AC power from an external commercial AC power supply 1; a boost chopper circuit 3 for boosting the rectified DC power; an inverter circuit / heating circuit 4 for generating AC power of a desired frequency from the boosted DC power and generating a filament current; and a high voltage generating circuit 5 for generating a desired high voltage tube voltage from the AC power of a desired frequency output by the inverter circuit / heating circuit 4.

[0030] The control unit 8 has a fluoroscopic mode and a photographing mode. When the operator turns on the fluoroscopic switch 320a of the operation unit 320 and instructs to perform fluoroscopic operation, the control unit 8 performs the fluoroscopic mode. That is, the control unit 8 supplies a filament current to one of the first filament and the second filament from the inverter circuit / heating circuit 4 and the high voltage generating circuit 5, and applies a tube voltage between the anode 10 and the filament 20. As a result, the electron beam is irradiated from the first filament and the second filament supplied with the filament current to the anode 10, and a relatively small dose of X-rays is emitted from the anode 10.

[0031] The irradiated X-rays pass through the subject and are detected by the X-ray detector 210. The image processing device 310 generates an image at a predetermined rate (for example, 30 frames / s) based on the output of the X-ray detector 210, and displays it on the display device 330. Thus, a fluoroscopic image (dynamic image) is displayed on the display device 330.

[0032] On the other hand, when the operator turns on the imaging switch 320b of the operation unit 320 and instructs to execute imaging, the control unit 8 executes the imaging mode. That is, the control unit 8 starts to supply a filament current larger than that in the fluoroscopy mode to one of the first filament and the second filament from the inverter circuit / heating circuit 4 and the high voltage generating circuit 5, and when a predetermined standby time has passed, a tube voltage larger than that in the fluoroscopy mode is applied between the anode 10 and the filament 20. Thus, a larger dose of X-rays than that in the fluoroscopy mode is radiated from the anode 10.

[0033] 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 based on the output of the X-ray detector 210 and displays it on the display device 330. Thus, the display device 330 displays the captured image.

[0034] In this embodiment, the control unit 8 sets the length of the standby time when the photographing mode is executed. At this time, the length of the standby time is set based on whether the filament current is supplied from the inverter circuit / heating circuit 4 and the high voltage generating circuit 5 to the filament used in the photographing mode, out of the first filament 21 and the second filament 22, before the photographing mode is executed this time.

[0035] Specifically, when the control unit 8 switches from the perspective mode to the photographing mode after executing the perspective mode, the predetermined first waiting time is set as the waiting time when a filament different from the filament used in the perspective mode among the first filament 21 and the second filament 22 is used in the photographing mode. When the same filament as the filament used in the perspective mode is used in the photographing mode, a second waiting time shorter than the first waiting time is set.

[0036] Below, use Figure 4 The process of FIG. 8 is used to explain the operation of the control unit 8 in more detail. Figure 4 The process is to first perform perspective, and then switch to photography and take pictures during the perspective process.

[0037] The control unit 8 is composed of a computer or the like having a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), and a memory. The CPU reads and executes a program stored in the memory (storage unit) to realize Figure 4 In addition, the control unit 8 may be partially or entirely constituted by hardware. For example, a custom IC such as an ASIC (Application Specific Integrated Circuit) or a programmable IC such as an FPGA (Field-Programmable Gate Array) may be used to design a circuit to implement Figure 4 The action of the process.

[0038] (Step S101)

[0039] When the operator turns on the power of the device or when the operator instructs to start the inspection by operating the input unit 320 c , the control unit 8 receives these operations and starts rotating the anode 10 .

[0040] (Step S102)

[0041] Next, when the operator presses the fluoroscopy switch 320 a to indicate the start of fluoroscopy, the control unit 8 receives the instruction, supplies a specified filament current to the filament used in fluoroscopy (the first filament 21 for small focus or the second filament 22 for large focus), and applies a specified tube voltage between the anode 10 and the filament 20 .

[0042] The filament 20 used in fluoroscopy uses a predetermined filament (here, the first filament 21 for small focus). However, the designation of the filament 20 used in fluoroscopy may be received from the operator via the input unit 320 c .

[0043] Thereby, a small dose of X-rays for fluoroscopy is generated and irradiated to the subject.

[0044] The X-ray detector 210 detects X-rays that have passed 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 (eg, 30 frames / s), and displays it on the display device 330 .

[0045] (Step S103)

[0046] The control unit 8 receives the brightness information of the generated fluoroscopic image from the image processing device 310 , and performs feedback control to increase the filament current or the tube voltage when the brightness is lower than a predetermined value.

[0047] (Step S104)

[0048] The control unit 8 calculates the photographic conditions when switching to photography (selection of whether the filament used in photography is the first filament 21 or the second filament 22, the filament current supplied, and the tube voltage) based on the fluoroscopy conditions (whether the filament used in fluoroscopy is the first filament 21 or the second filament 22, the filament current supplied, and the tube voltage) with reference to a pre-calculated table or mathematical formula.

[0049] Since the fluoroscopic conditions (filament current, tube voltage) are feedback-controlled in step S103, the state of the subject (thickness or part of the subject) is reflected. Therefore, the relationship between the fluoroscopic conditions and the imaging conditions is obtained in advance by experiments or calculations, and a table or mathematical formula is prepared, thereby being able to calculate appropriate imaging conditions corresponding to the state of the subject.

[0050] (Steps S105, S106)

[0051] The control unit 8 repeats steps S103 and S104 to continue the fluoroscopy until the pressing of the imaging switch is received.

[0052] When the imaging switch is pressed, the process proceeds to step S106, where the supply of the filament current to the fluoroscopy filament and the supply of the tube voltage between the anode 10 and the filament 20 are stopped, and fluoroscopy is terminated.

[0053] (Steps S107, S108, S109)

[0054] Next, the control unit 8 determines whether the filament for imaging calculated (selected) in step S104 is the same filament as the filament used for fluoroscopy (step S107). If the filaments are different, the filament used for imaging is in a state of not being heated at all, so the process proceeds to step S109, and a predetermined standby time (heating time) is set (step S109).

[0055] The standby time (heating time) is the time required for the temperature of the imaging filament to rise to a temperature capable of emitting a large dose of electron beams emitted from the anode 10 used in imaging when the filament current is supplied to the filament that is not heated at all. The standby time (heating time) is a time predetermined for each of the first filament 21 and the second filament 22. The time is selected and set based on the same filament used in imaging calculated in step S104.

[0056] (Step S108)

[0057] On the other hand, in step S106, in the control unit 8, when the filament for imaging calculated (selected) in step S104 is the same filament as the filament used in fluoroscopy, since the filament current has been supplied during fluoroscopy and has been heated to a certain extent, the time required to increase the temperature from this state to a state capable of irradiating a large dose used in imaging can be shorter than the waiting time (heating time) in step S109. Therefore, the process proceeds to step S108 to calculate and set the heating time.

[0058] Specifically, the control unit 8 calculates the difference between the filament current supplied to the filament during fluoroscopy adjusted in step S103 and the imaging filament current calculated in step S104. Based on the obtained difference, the control unit 8 calculates the heating time required to raise the imaging filament to a temperature capable of irradiating a large dose, using a table or a mathematical formula indicating the relationship between the difference and the required heating time obtained in advance by experiments or calculations.

[0059] In addition, in addition to the above-mentioned difference, these tables or mathematical formulas may also include the imaging filament current, the outside air temperature, etc. as parameters.

[0060] (Step S110)

[0061] The control unit 8 starts supplying the filament current calculated in step S104 to the imaging filament selected in step S104 .

[0062] (Step S111)

[0063] When the heating time (waiting time) of the imaging filament set in step S109 or S108 has elapsed, the control unit 8 determines that the temperature of the imaging filament has risen to a temperature capable of irradiating an electron beam capable of releasing a large dose of imaging from the anode 10 , and proceeds to step S112 .

[0064] (Step S112)

[0065] 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 a large dose of X-rays for imaging.

[0066] The X-rays pass through the subject and are detected by the X-ray detector 210 . The image processing device 310 generates one image (X-ray image) and displays it on the display device 330 .

[0067] According to this embodiment, when the filament used for fluoroscopy is the same as the filament used for imaging, the waiting time for heating is shortened, thereby shortening the waiting time for the operator. Therefore, the convenience for the operator is improved and the stress on the operator can be reduced.

[0068] <<Implementation Method 2>>

[0069] use Figure 5 The X-ray fluoroscopy imaging device of the second embodiment is described with reference to the flowchart of the embodiment. The device structure of the X-ray fluoroscopy imaging device of the second embodiment is the same as that of the first embodiment. Figure 5 In the process of implementation mode 1, Figure 4 The same steps in the process are marked with the same numbers.

[0070] In the second embodiment, when different filaments are used in fluoroscopy and photography, when the control unit 8 is executing the photography mode, when the filament current was supplied to the first filament 21 and the second filament 22 used in the photography mode in the photography mode before the photography mode executed this time, the standby time is set according to the length of the rest time during which the filament current was not supplied from the previous photography mode to the current photography mode.

[0071] use Figure 5 The specific actions of the control unit 8 are explained in the following process.

[0072] (Step S101)

[0073] Implementation 1 Figure 4 In the same manner as in the process of FIG. 1 , the control unit 8 starts the rotation of the anode 10 .

[0074] (Step S202)

[0075] The difference from the first embodiment is that when the operator presses the perspective switch 320 a , the control unit 8 always selects the first filament 21 with a small focal spot size. A predetermined filament current is supplied to the small focal spot filament, and a tube voltage is applied between the anode 10 and the filament 20 .

[0076] (Steps S103 to S106)

[0077] As in the first embodiment, fluoroscopy is performed, imaging conditions are calculated, and when the imaging switch 320b is pressed, fluoroscopy is terminated.

[0078] (Steps S107, S209)

[0079] In step S107 , when the imaging filament calculated (selected) in step S104 is the second filament with a large focal size, the control unit 8 sets the waiting time in step S209 based on the rest time counted in step S214 described later.

[0080] What is counted in step S214 is the time during which no current is supplied to the second filament 22 of the large focal size from the last photography mode to the current photography mode. During the last photography, the photography filament current was supplied to the second filament 22, and the temperature rose, but the temperature gradually dropped during the rest time. Therefore, if the rest time is short, the time required to heat the second filament 22 to a state where a large dose for photography can be released in this photography is short. However, if the rest time is long, the time required to heat the second filament 22 to a state where a large dose for photography can be released in this photography will be longer.

[0081] Therefore, in the second embodiment, in step S209 , the heating time (waiting time) is calculated and set based on the rest time counted in step S214 by referring to a table obtained in advance by experiments or calculations.

[0082] (Steps S108, S110-S112)

[0083] When the imaging filament calculated (selected) in step S104 is the second filament with a large focal size, in step S108 , the control unit 8 calculates and sets the heating time based on the difference in filament current between the fluoroscopy and imaging, similarly to the first embodiment.

[0084] Steps S110 to S112 are performed in the same manner as in the first embodiment. When the filament current starts to be supplied to the second filament 22 with a large focal spot size, the tube voltage is applied after the heating time (waiting time) set in step S209 or S108 has elapsed, and imaging is performed.

[0085] (Steps S213, S214)

[0086] The control unit 8 proceeds to step S213, and when the imaging filament selected in step S104 is the second filament 22 with a large focal size, the control unit 8 proceeds to step S214 to count the rest time until the imaging switch 320b is pressed next time.

[0087] According to the second embodiment, in addition to the effects of the first embodiment, even when the filament used for fluoroscopy is different from the filament used for imaging, if the time elapsed from the last imaging is short, the standby time (heating time) is shortened. Therefore, compared with the first embodiment, the convenience for the operator is further improved.

[0088] <<Implementation Method 3>>

[0089] use Figure 6 The X-ray fluoroscopy imaging device of the third embodiment is described with reference to the flowchart of the embodiment. The device structure of the X-ray fluoroscopy imaging device of the third embodiment is the same as that of the first embodiment. Figure 6In the process of implementation mode 1, Figure 4 The same steps in the process are marked with the same numbers.

[0090] In the third embodiment, when the imaging mode is executed, the control unit 8 receives information on the imaging site and thickness of the subject from the input unit 320c of the operation unit 320, and selects a filament to be used for imaging from the first filament 21 and the second filament 22. The selected filament is also used in fluoroscopy.

[0091] As a result, when switching from fluoroscopy to imaging, the filament does not need to be switched, so the time required to heat the filament for imaging is shortened.

[0092] (Steps S301, S302)

[0093] First, the control unit 8 receives selection of an examination site (head, abdomen, feet, etc.) from the operator via the input unit 320 c (step S301 ), and then receives input of the thickness of the examination site of the subject (step S302 ).

[0094] (Step S303)

[0095] The control unit 8 selects the first filament 21 or the second filament 22 as the imaging filament based on the inspection part and the body thickness received in steps S301 and S302, with reference to a predetermined table or mathematical formula. In the table, for each combination of the inspection part and the body thickness obtained in advance by experiments or calculations, an imaging filament suitable for the combination (either the first filament 21 with a small focal spot size or the second filament 22 with a large focal spot size) is determined.

[0096] Thus, the control unit 8 can select the imaging filament suitable for the combination of the examination part and the body thickness of the subject to be imaged.

[0097] (Step S101)

[0098] Next, the control unit 8 proceeds to step S101 , and similarly to the first embodiment, when receiving an instruction to start the inspection from the operator, the control unit 8 starts rotating the anode 10 .

[0099] (Steps S304 to S306)

[0100] The control unit 8 selects the same filament as the imaging filament selected in step S303 as the fluoroscopy filament.

[0101] Specifically, when the imaging filament selected in step S303 is the first filament 21 with a small focal size (step S304 ), the first filament 21 with a small focal size is selected as the fluoroscopy filament (step S305 ).

[0102] When the imaging filament selected in step S303 is not the first filament 21 having a small focal size (step S304 ), the second filament 22 having a large focal size is selected as the fluoroscopy filament (step S305 ).

[0103] (Steps S102, S103)

[0104] Next, similar to steps S102 and S103 of the first embodiment, when the operator presses the fluoroscopy switch 320a, the control unit 8 supplies a predetermined filament current to the fluoroscopy filament selected in steps S304 to S306 and applies a predetermined tube voltage between the anode 10 and the filament 20, thereby starting fluoroscopy.

[0105] Furthermore, the control unit 8 receives the brightness information of the fluoroscopic image from the image processing device 310 and performs feedback control on the filament current or the tube voltage.

[0106] (Step S307)

[0107] Next, similarly to step S104 of embodiment 1, the control unit 8 calculates the imaging conditions (filament current, tube voltage) when switching to imaging based on the fluoroscopy conditions (filament current, tube voltage) by referring to a pre-calculated table or mathematical formula. However, unlike step S104 of embodiment 1, since the filament used for imaging has been determined as the filament used for fluoroscopy, the filament used for imaging is not selected.

[0108] (Steps S105-S106, S108, S110-S112)

[0109] Next, the control unit 8 executes steps S105 to S106, S108, and S110 to S112 of the first embodiment. That is, the control unit 8 continues to perform fluoroscopy until the imaging switch is pressed. If the imaging switch is pressed, the fluoroscopy is terminated, and the heating time required to raise the imaging filament, which is the same as the fluoroscopy filament, to a temperature capable of irradiating a large dose is calculated and set. The imaging filament current calculated in step S307 is started to be supplied to the imaging filament, and when the heating time (standby time) set in step S108 has passed, the tube voltage is applied, and a large dose of X-rays for imaging is irradiated to perform imaging.

[0110] According to this embodiment, since the same filament is selected in advance for fluoroscopy and imaging according to the part and thickness of the subject, the waiting time for heating is always shortened. Therefore, the operator's waiting time is shortened and the convenience of the operator is improved.

Claims

1. An X-ray fluoroscopic imaging device, characterized in that: The X-ray fluoroscopic imaging device comprises: an X-ray tube for irradiating an object with X-rays; a voltage device connected to the X-ray tube; and a control unit for controlling the voltage device. An X-ray detector detects X-rays transmitted through the subject; and an operation unit, The X-ray tube includes an anode and a filament for irradiating an electron beam toward the anode, wherein the filament includes a first filament having a smaller 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 perspective mode and a photography 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 radiate a small dose of X-rays from the anode. In the photography mode, when the control unit receives a photography instruction from the operation unit, after supplying a filament current larger than that in the fluoroscopy mode to one of the first filament and the second filament, after a predetermined standby time has elapsed, the control unit applies a tube voltage larger than that in the fluoroscopy mode to radiate a large dose of X-rays from the anode. When the photographing mode is executed, the control unit sets the length of the standby time according to whether a filament current was supplied to a filament used in the photographing mode, out of the first filament and the second filament, before the photographing mode is executed this time.

2. The X-ray fluoroscopic imaging device according to claim 1, characterized in that: When the control unit switches from the perspective mode to the photographing mode and executes the switching after executing the perspective mode, when a filament different from the filament used in the perspective mode among the first filament and the second filament is used in the photographing mode, a predetermined first waiting time is set as the waiting time, and when a filament the same as the filament used in the perspective mode is used in the photographing mode, a second waiting time shorter than the first waiting time is set as the waiting time.

3. The X-ray fluoroscopic imaging device according to claim 1, characterized in that: When executing the photography mode, the control unit sets the standby time based on the difference between the supplied filament current and the filament current supplied in the photography mode when a filament current was supplied to the filament used in the photography mode among the first filament and the second filament before the photography mode is executed this time.

4. The X-ray fluoroscopic imaging device according to claim 1, characterized in that: When executing the photography mode, the control unit calculates the filament current in the photography mode based on the filament current in the photography mode, when the filament current is supplied to the filament used in the photography mode, out of the first filament and the second filament, in the perspective mode before the photography mode is executed this time.

5. The X-ray fluoroscopic imaging device according to claim 1, characterized in that: When the control unit executes the photographic mode, when filament current was supplied to the filament used in the photographic mode among the first filament and the second filament in the photographic mode before the photographic mode executed this time, the standby time is set according to the length of the rest time during which the filament current was not supplied from the previous photographic mode to the current photographic mode.

6. The X-ray fluoroscopic imaging device according to claim 1, characterized in that: The control unit receives information about an imaging site of the 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 also uses the selected filament in the fluoroscopy mode.

7. The X-ray fluoroscopic imaging device according to claim 1, characterized in that: The control unit refers to a pre-calculated table to determine whether the filament used in the perspective mode is the first filament or the second filament, one or more of the filament current and the tube voltage when the perspective mode is switched to the photography mode, based on whether the filament used in the perspective mode is the first filament or the second filament, and one or more of the filament current and the tube voltage supplied to the filament in the perspective mode.

8. The X-ray fluoroscopic imaging device according to claim 1, characterized in that: The control unit performs feedback control on at least one of a filament current and a tube voltage based on a detection result of the X-ray detector while the fluoroscopy mode is being executed.

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