JP2017064392A - X-ray computer tomography apparatus and x-ray tube device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of an X-ray tube caused by warm up.SOLUTION: An X-ray tube 13 includes: a negative electrode 131 generating thermal electron; a positive electrode 133 receiving the thermal electron from the negative electrode 131 to generate X-rays; and an adjuster 137 applying an electric field or a magnetic field for focusing or deviating the thermal electron from the negative electrode 131. An X-ray detector 15 detects X-rays generated from the positive electrode 133. The data collection circuit 27 collects data corresponding to the X-rays detected by the X-ray detector 15. An image reconstruction circuit 51 generates images on the basis of the collected data. An adjuster control circuit 45 controls the adjuster 137 for changing at least one of the size and the position of a focus point of the thermal electron at the positive electrode 133 from the negative electrode 131, by scanning and warming up.SELECTED DRAWING: Figure 2

Description

  Embodiments described herein relate generally to an X-ray computed tomography apparatus and an X-ray tube apparatus.

  The X-ray computed tomography apparatus is equipped with an X-ray tube that generates X-rays. Before scanning, to maintain the cleanliness in the X-ray tube and to raise the temperature of parts such as the rotating anode in the X-ray tube to a specified value or higher, high voltage application and filament heating current The X-ray tube is warmed up by the supply.

  In warm-up, since the cathode used for scanning is diverted, there is a possibility that the life of the cathode may be shortened for purposes other than scanning. Moreover, since the size of the focal point is fixed, the surface of the anode may be roughened.

JP 2004-296242 A JP 2011-238614 A JP 2002-319359 A

  An object is to provide an X-ray computed tomography apparatus and an X-ray tube apparatus that can suppress the deterioration of the X-ray tube caused by warm-up.

The X-ray computed tomography apparatus according to the present embodiment focuses on or deflects a cathode that generates thermoelectrons, an anode that generates X-rays by receiving thermoelectrons from the cathode, and thermoelectrons from the cathode. An X-ray tube having a controller for applying an electric field or a magnetic field, an X-ray detector for detecting X-rays generated from the anode, and data corresponding to the X-rays detected by the X-ray detector A data collection unit for collecting the image, an image generation unit for generating an image based on the collected data,
And a controller that controls the adjuster to switch at least one of the size and position of the focus of the thermoelectrons from the cathode at the anode between scanning and warming up.

FIG. 1 is a diagram showing a configuration of an X-ray computed tomography apparatus according to the present embodiment. FIG. 2 is a diagram illustrating a configuration of the X-ray tube and the high voltage generator according to the first embodiment. FIG. 3 is a front view of the anode showing the focus size for scanning and the focus size for warm-up according to the first embodiment. FIG. 4 is a side view of the anode showing the focus size for scanning and the focus size for warm-up according to the first embodiment. FIG. 5 is a front view of the anode in which the focus position for scanning and the focus position for warm-up according to another embodiment 1 are shown. FIG. 6 is a side view of the anode showing the focus position for scanning and the focus position for warm-up according to another embodiment. FIG. 7 is a diagram illustrating a timing chart of the heating current and the tube voltage regarding the focus size switching according to the first embodiment. FIG. 8 is a diagram illustrating a configuration of an X-ray tube and a high voltage generator according to the second embodiment. FIG. 9 is a front view of the anode showing the focus size for scanning and the focus size for warm-up according to the second embodiment. FIG. 10 is a side view of the anode showing the focus size for scanning and the focus size for warm-up according to the second embodiment. FIG. 11 is a diagram illustrating a timing chart of the heating current and tube voltage related to filament switching according to the second embodiment.

  Hereinafter, an X-ray computed tomography apparatus and an X-ray tube apparatus according to this embodiment will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of an X-ray computed tomography apparatus according to this embodiment. As shown in FIG. 1, the X-ray computed tomography apparatus according to this embodiment includes a gantry device 10 and a console 50. For example, the gantry device 10 is installed in a CT examination room, and the console 50 is installed in a control room adjacent to the CT examination room. The gantry device 10 and the console 50 are connected to each other in a wired or wireless manner so that they can communicate with each other. The gantry device 10 is a scanning device having a configuration for performing X-ray computed tomography (hereinafter referred to as X-ray CT imaging) of the subject S. The console 50 is a computer that controls the gantry device 10.

  As shown in FIG. 1, the gantry device 10 includes a substantially cylindrical rotating frame 11 in which an opening forming a photographing space (field of view) is formed. As shown in FIG. 1, an X-ray tube 13 and an X-ray detector 15 arranged so as to face each other with an opening interposed therebetween are attached to the rotating frame 11. The rotating frame 11 is a metal frame formed in an annular shape from a metal such as aluminum. For example, the X-ray tube 13 and the X-ray detector 15 may be fitted into a recess formed in the rotating frame 11 or may be fastened by a fastener such as a screw. More specifically, the gantry device 10 includes a main frame (not shown) formed of a metal such as aluminum. The rotating frame 11 is supported by the main frame so as to be rotatable around a central axis Z via a bearing or the like. An annular electrode (not shown) is provided at a contact portion of the main frame with the rotating frame 11. A conductive slider (not shown) is attached to the contact portion of the main frame so as to be in sliding contact with the annular electrode. Various electric power such as an X-ray detector 15 and a high voltage generator 17 mounted on the rotating frame 11 is supplied with power from a power supply device (not shown) accommodated in the gantry device 10 via the annular electrode and the slider. Supplied to the equipment.

  The X-ray tube 13 is connected to a high voltage generator 17. The high voltage generator 17 is attached to the rotating frame 11, for example. The high voltage generator 17 generates a high voltage to be applied to the X-ray tube 13 from the power supplied from the power supply device (not shown) of the gantry via the annular electrode and the slider according to the control of the gantry control circuit 25. Generate and supply filament heating current. The high voltage generator 17 and the X-ray tube 13 are connected via a high voltage cable (not shown). The high voltage generated by the high voltage generator 17 is applied to the X-ray tube 13 via a high voltage cable. Further, the filament heating current generated by the high voltage generator 17 is applied to the X-ray tube 13 via a high voltage cable.

  A front collimator 19 is attached in front of the X-ray irradiation window of the X-ray tube 13. The front collimator 19 limits the irradiation field of the X-rays emitted from the X-ray tube 13. More specifically, the front collimator 19 has a diaphragm blade formed of a material that attenuates X-rays. The irradiation field is defined by the opening formed by the diaphragm blades. The diaphragm blade may be formed of any material as long as it is a material that attenuates X-rays. For example, it may be formed of heavy metal such as lead.

  An FOV (field of view) is set in an opening (bore) of the rotating frame 11. A top plate 21 is inserted into the opening of the rotating frame 11. A subject S is placed on the top plate 21. The top 21 is positioned so that the imaging region of the subject S placed on the top 21 is included in the FOV. The rotating frame 11 receives power from the rotation driving device 23 and rotates around the central axis Z at a constant angular velocity. An arbitrary motor such as a direct drive motor or a servo motor is used as the rotation drive device 23. The rotation drive device 23 is accommodated in the gantry device 10, for example. The rotation drive device 23 receives the drive signal from the gantry control circuit 25 and generates power for rotating the rotary frame 11.

  The X-ray detector 15 detects X-rays generated from the X-ray tube 13. Specifically, the X-ray detector 15 has a plurality of detector pixels (not shown) arranged on a two-dimensional curved surface. Each detector pixel has a scintillator and a photoelectric conversion element. A scintillator is a substance that converts X-rays into fluorescence. As the scintillator substance, for example, NaI or BGO is used. The scintillator converts incident X-rays into a number of fluorescent photons according to the intensity of the incident X-rays. The photoelectric conversion element is a circuit element that amplifies fluorescence and converts it into an electric signal. For example, a photomultiplier tube or a photodiode is used as the photoelectric conversion element. The detector pixel may be an indirect detection type that detects X-rays after converting them to light as described above, or may be a direct-conversion type that directly converts X-rays into electrical signals. As the direct detection type detector pixel, for example, a type including a semiconductor diode in which electrodes are attached to both ends of a semiconductor is applicable.

  A data acquisition circuit 27 is connected to the X-ray detector 15. The data collection circuit 27 collects data (hereinafter referred to as raw data) corresponding to the intensity of the X-ray detected by the X-ray detector 15 from the X-ray detector 15 for each view. Specifically, the data collection circuit 27 includes, for example, an integration circuit (not shown) and an A / D converter (not shown) for each detector pixel. The integration circuit integrates the electric signal from the detector pixel for each view. The A / D converter converts the integrated electrical signal from an analog signal to a digital signal (raw data). Thereby, raw data for each view is collected. The raw data is a set of digital values indicating the intensity of the x-ray identified by the source detector pixel channel number, column number and view number indicating the collected view. The raw data is supplied to the console 50 through, for example, a non-contact data transmission device (not shown) accommodated in the gantry device 10. The data collection circuit 27 may be mounted with other circuit elements such as a preamplifier and an IV converter. The data collection circuit 27 includes a semiconductor integrated circuit such as an ASIC (Application Specific Integrated Circuit), and circuit elements such as the integration circuit and the A / D converter are mounted on the semiconductor integrated circuit.

  The gantry control circuit 25 synchronously controls the high voltage generator 17, the rotation drive device 23, and the data acquisition circuit 27 in accordance with control from the system control circuit 61 of the console 50, and performs X-ray CT imaging of the subject S. As hardware resources, the gantry control circuit 25 includes a processing device (processor) such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit) and a storage device such as a ROM (Read Only Memory) and a RAM (Random Access Memory). Memory). The gantry control circuit 25 may be provided in the gantry device 10, may be provided in the console 50, or may be provided in a device separate from the gantry device 10 and the console 50. The gantry control circuit 25 includes an application specific integrated circuit (ASIC), a field programmable gate device (FPGA), and other complex programmable logic devices (Complex Programmable Logic Devices). CPLD) and a simple programmable logic device (SPLD). The processing device implements the above functions by reading and executing a program stored in the storage device. Instead of storing the program in the storage device, the program may be directly incorporated in the circuit of the processing device. In this case, the processing device realizes the above function by reading and executing the program incorporated in the circuit.

  As shown in FIG. 1, the console 50 includes an image reconstruction circuit 51, an image processing circuit 53, a display circuit 55, an input circuit 57, a main storage circuit 59, and a system control circuit 61 connected via a bus. Have. Data communication among the image reconstruction circuit 51, the image processing circuit 53, the display circuit 55, the input circuit 57, the main memory circuit 59, and the system control circuit 61 is performed via a bus.

  The image reconstruction circuit 51 reconstructs an image related to the subject S based on the raw data from the gantry device 10. Specifically, the image reconstruction circuit 51 includes a data storage circuit 511, a preprocessing unit 513, and a reconstruction processing unit 515. The data storage circuit 511 is a storage device such as a hard disk drive (HDD), a solid state drive (SSD), or an integrated circuit storage device that stores raw data transmitted from the gantry device 10. The preprocessing unit 513 performs preprocessing such as logarithmic conversion and metal artifact reduction processing on the raw data. The reconstruction processing unit 515 generates a CT image representing the spatial distribution of CT values depending on the X-ray attenuation coefficient based on the raw data after preprocessing. Image reconstruction algorithms include analytical image reconstruction methods such as FBP (filtered back projection) and CBP (convolution back projection), ML-EM (maximum likelihood expectation maximization), and OS-EM (ordered subset). An existing image reconstruction algorithm such as a statistical image reconstruction method such as an expectation maximization method may be used.

  The image reconstruction circuit 51 includes, as hardware resources, a processing device (processor) such as a CPU, MPU, or GPU (Graphics Processing Unit) and a storage device (memory) such as a ROM or RAM. The image reconstruction device 51 may be realized by an ASIC, FPGA, CPLD, or SPLD. The processing device implements the function of the preprocessing unit 513 and the function of the reconstruction processing unit 515 by reading and executing a program stored in the storage device. Instead of storing the program in the storage device, the program may be directly incorporated in the circuit of the processing device. In this case, the processing apparatus implements the function of the reconstruction processing unit 515 by reading and executing a program incorporated in the circuit. In addition, a dedicated hardware circuit that realizes the function of the preprocessing unit 513 and a dedicated hardware circuit that realizes the function of the reconstruction processing unit 515 may be mounted in the image reconstruction circuit 51.

  The image processing device 53 performs various image processing on the CT image reconstructed by the image reconstruction circuit 51. For example, when the CT image is volume data, the image processing circuit 53 performs volume rendering, surface volume rendering, image value projection processing, MPR (Multi-Planer Reconstruction) processing, CPR (Curved MPR) processing, etc. on the CT image. A display image is generated by performing three-dimensional image processing. The image processing circuit 53 includes, as hardware resources, a processing device (processor) such as a CPU, MPU, or GPU and a storage device (memory) such as a ROM or RAM. The image processing circuit 53 may be realized by an ASIC, FPGA, CPLD, or SPLD.

  The display circuit 55 displays various data such as a two-dimensional CT image and a display image. Specifically, the display circuit 55 includes a display interface circuit and a display device. The display interface circuit converts data representing a display target into a video signal. The display signal is supplied to the display device. The display device displays a video signal representing a display target. As the display device, for example, a CRT display, a liquid crystal display, an organic EL display, an LED display, a plasma display, or any other display known in the art can be used as appropriate.

  The input circuit 57 inputs various commands from the user. Specifically, the input circuit 57 includes an input device and an input interface circuit. The input device accepts various commands from the user. As an input device, a keyboard, a mouse, various switches, and the like can be used. The input interface circuit supplies an output signal from the input device to the system control circuit 61 via the bus. The input circuit 57 may be provided on the console 50 or may be provided on the gantry device 10.

  The main storage circuit 59 is a storage device such as an HDD, an SSD, or an integrated circuit storage device that stores various information. Further, the main storage circuit 59 may be a drive unit that reads / writes various information from / to a portable storage medium such as a CD-ROM drive, a DVD drive, or a flash memory. For example, the main memory circuit 59 stores a control program related to the X-ray CT imaging according to the present embodiment.

  The system control circuit 61 includes, as hardware resources, a processing device (processor) such as a CPU or MPU and a storage device (memory) such as a ROM or RAM. The system control circuit 61 may be realized by an ASIC, FPGA, CPLD, or SPLD. The system control circuit 61 functions as the center of the X-ray computed tomography apparatus according to this embodiment. Specifically, the system control circuit 61 reads out a control program stored in the main storage circuit 59 and develops it on the memory, and controls each part of the X-ray computed tomography apparatus according to the developed control program.

  The image reconstruction circuit 51, the image processing circuit 53, and the system control circuit 61 may be integrated into a single circuit within the console 50, or may be distributed over a plurality of circuits. Further, the image reconstruction circuit 51, the image processing circuit 53, and the system control circuit 61 may be integrated on a single board in the console 50, or may be distributed on a plurality of boards.

  Hereinafter, details of the X-ray computed tomography apparatus according to the present embodiment will be described in detail in Example 1 and Example 2.

Example 1
FIG. 2 is a diagram illustrating a configuration of the X-ray tube 13 and the high voltage generator 17 according to the first embodiment. As shown in FIG. 2, the X-ray tube 13 contains a cathode 131, an anode 133, a rotor 135, and a regulator 137. The cathode 131 is made of a metal having a thin line shape or a plate shape. In the case of a fine wire shape, the cathode 131 is excellent in thermal response compared to the case of having a plate shape, and the characteristics are well known empirically. When it has a plate shape, the cathode 131 has a longer life than when it has a fine line shape. Hereinafter, the cathode 131 is assumed to be a filament realized by a metal such as tungsten or nickel having a thin line shape. The filament 131 is connected to the high voltage generator 17 via a cable or the like. The filament 131 receives the supply of the filament heating current from the high voltage generator 17 and generates heat to emit thermoelectrons.

  The anode 133 is an electrode having a disk shape made of heavy metal such as tungsten or molybdenum. The rotor 135 is attached to the anode 133. As the rotor 135 rotates about the axis, the anode 133 rotates. The anode 133 and the rotor 135 constitute a rotating anode. A high voltage is applied between the filament 131 and the anode 133 by the high voltage generator 17. The thermoelectrons generated from the filament 131 are accelerated while being focused in a beam shape by a high voltage applied between the filament 131 and the anode 133, and collide with the rotating anode 133. The anode 133 receives the thermal electrons from the filament 131 and emits braking X-rays.

  The regulator 137 is disposed between the filament 131 and the anode 133. The adjuster 137 electrically or magnetically adjusts the focal spot size on the surface of the anode 133. The adjuster 137 may be any hardware that deflects the orbit of thermoelectrons electrically or magnetically. For example, the adjuster 137 is realized by an electrode, a magnet, a coil, or the like. Hereinafter, the regulator 137 is assumed to be an electrode. The adjuster 137 receives the application of the voltage from the high voltage generator 17, deflects the trajectory of the thermal electrons flying from the filament 131 to the anode 133, and adjusts the focal spot size.

  The high voltage generator 17 applies a high voltage to the X-ray tube 13 according to control by the gantry control circuit 25 and supplies a filament heating current. The high voltage generator 17 according to the first embodiment scans the size of the focus at the anode 133 of thermoelectrons from the cathode 131 included in the X-ray tube 13 by using a focus size variable function (FSC: focus size control). Switch selectively with warm-up. Specifically, the high voltage generator 17 includes a power supply circuit 31, a high voltage generation circuit 33, a filament heating circuit 35, a tube voltage detector 37, a tube current detector 39, a tube voltage control circuit 41, and a tube current control circuit 43. And a regulator control circuit 45.

  The power supply circuit 31 generates direct current based on alternating current from power supply equipment provided in an examination room or the like in which the gantry device 10 is installed. Specifically, the power supply circuit 31 includes a rectifier circuit and a smoothing capacitor. The rectifier circuit rectifies alternating current from the power supply facility into direct current. The smoothing capacitor smoothes the alternating current rectified by the rectifier circuit. This rectification and smoothing converts alternating current into direct current. In addition, the power supply which supplies electric power to the power supply circuit 31 is not limited only to power supply equipment, A capacitor | condenser and a storage battery may be sufficient.

  The high voltage generation circuit 33 generates a high voltage applied to the X-ray tube 13 in accordance with control by the tube voltage control circuit 41. The high voltage generation circuit 33 and the anode 133 are connected by an anode side high voltage cable, and the high voltage generation circuit 33 and the filament 131 are connected by a cathode side high voltage cable. The high voltage generation circuit 33 can be applied to any type such as a transformer type X-ray high voltage device, a constant voltage type X-ray high voltage device, a capacitor type X-ray high voltage device, and an inverter type X-ray high voltage device. For example, in the case of an inverter type, the high voltage generation circuit 33 includes an inverter and a high voltage converter. The inverter switches the direct current from the power supply circuit 31 at a timing according to the control by the tube voltage control circuit, and converts it into an alternating output pulse. The high voltage converter converts an AC output pulse from the inverter into a DC high voltage.

  The filament heating circuit 35 generates electric power for heating the filament 131 according to the control by the tube current control circuit 43. As the filament heating circuit 35, either a variable resistance method or a high-frequency heating method can be applied. For example, in the case of the high frequency heating method, the filament heating circuit 35 includes an inverter and a filament heating transformer. The inverter switches the direct current from the power supply circuit 31 at a timing according to the control by the tube voltage control circuit, and converts it into an alternating output pulse. The filament heating transformer converts an AC output pulse from the inverter into a DC filament heating current.

  A tube voltage detector 37 is connected between the anode side high voltage cable and the cathode side high voltage cable. The tube voltage detector 37 detects a high voltage applied between the cathode 131 and the anode 133 as a tube voltage. Data of the detected tube voltage value (hereinafter referred to as tube voltage detection value) is supplied to the tube voltage control circuit 41.

  A tube current detector 39 is connected to the anode side cable. The tube current detector 39 detects the current that flows through the anode-side cable due to the flow of thermoelectrons from the cathode 131 to the anode 133 as a tube current. Data of the detected tube current value (hereinafter referred to as a tube current detection value) is supplied to the tube current control circuit 43.

  The tube voltage control circuit 41 controls the high voltage generation circuit 33 based on the comparison between the tube voltage detection value and the set tube voltage value. More specifically, the tube voltage control circuit 41 compares the tube voltage detection value with the set tube voltage value, and feedback-controls the high voltage generation circuit 33 so that the tube voltage detection value converges to the set tube voltage. Data of the set tube voltage value is supplied from the gantry control circuit 25.

  The tube current control circuit 43 controls the filament heating circuit 35 based on the comparison between the tube current detection value and the set tube current. More specifically, the tube current control circuit 43 compares the tube current detection value with the set tube current value, and feedback-controls the filament heating circuit 35 so that the tube current detection value converges to the set tube current value. Data of the set tube voltage value is supplied from the gantry control circuit 25.

  The regulator control circuit 45 controls the regulator 137 to switch at least one of the size and position of the focal point of the thermoelectron from the filament 131 at the anode 133 between scanning and warm-up. Specifically, when the controller control circuit 45 is supplied with a signal indicating that scanning is in progress (hereinafter referred to as a scan signal) from the gantry control circuit 25, the thermoelectrons from the filament 131 have a size for scanning. The adjuster 137 is controlled to focus on the focal point. When the scan signal is supplied from the gantry control circuit 25, the controller control circuit 45 causes the thermoelectrons from the filament 131 to collide with the focal position for scanning separately or in parallel with the focusing of the size. The controller 137 may be controlled. When a signal indicating that the warm-up is in progress (hereinafter referred to as a warm-up signal) is supplied from the gantry control circuit 25, the controller control circuit 45 causes the thermoelectrons to focus on the focal point of the warm-up size. The controller 137 is controlled. When the warm-up signal is supplied from the gantry control circuit 25, the controller control circuit 45 causes the thermoelectrons from the filament 131 to collide with the warm-up focal position separately or in parallel with the focusing of the size. The controller 137 may be controlled so as to. Strictly speaking, the focal position indicates the position of the focal point of the anode 133.

  The controller control circuit 45 stores in a memory or the like a pre-determined focus voltage value corresponding to the size of the scan focus F1 and a focus voltage value corresponding to the size of the warm-up focus F2. When a scan signal is supplied from the gantry control circuit 25 in the scan, the controller control circuit 45 reads a focused voltage value corresponding to the size of the focus F1 for scanning from a memory or the like, and corresponds to the read focused voltage value. The voltage to be applied is applied to the regulator 137. As a result, the focus F1 for scanning is switched. When the warm-up signal is supplied from the gantry control circuit 25 during the warm-up, the controller control circuit 45 reads the focus voltage value corresponding to the size of the focus F2 for warm-up from the memory or the like, and reads the read focus A voltage corresponding to the voltage value is applied to the regulator 137. As a result, the focus is switched to the warm-up focus F2. That is, the controller control circuit 45 can move the focal point to a different position in the rotational radius direction of the anode 133 during warm-up and during scanning.

  Similarly, the controller control circuit 45 stores a deflection voltage value corresponding to a predetermined position of the scanning focus F1 and a deflection voltage value corresponding to the position of the warm-up focus F2 in a memory or the like. Yes. When a scan signal is supplied from the gantry control circuit 25 in the scan, the controller control circuit 45 reads a deflection voltage value corresponding to the position of the focus F1 for scanning from a memory or the like, and corresponds to the read deflection voltage value. The voltage to be applied is applied to the regulator 137. As a result, the focus F1 for scanning is switched. When the warm-up signal is supplied from the gantry control circuit 25 during the warm-up, the controller control circuit 45 reads the deflection bundle voltage value corresponding to the position of the warm-up focal point F2 from the memory or the like and reads it out. A voltage corresponding to the deflection voltage value is applied to the regulator 137. As a result, the focus is switched to the warm-up focus F2. That is, the controller control circuit 45 can move the focal point to a different position in the rotational radius direction of the anode 133 during warm-up and during scanning.

  The tube voltage control circuit 41, the tube current control circuit 43, and the regulator control circuit 45 may be mounted on a single substrate or may be mounted on a plurality of substrates. The tube voltage control circuit 41, the tube current control circuit 43, and the regulator control circuit 45 may be realized by an analog circuit or a digital circuit. When implemented as a digital circuit, the tube voltage control circuit 41, the tube current control circuit 43, and the regulator control circuit 45 include, as hardware resources, a processing device (processor) such as a CPU or MPU and a storage device such as a ROM or RAM. (Memory). Further, the tube voltage control circuit 41, the tube current control circuit 43, and the regulator control circuit 45 may be realized by an ASIC, FPGA, CPLD, or SPLD.

  FIG. 3 is a front view of the anode 133 showing the focus size for scanning and the focus size for warm-up. FIG. 4 is a side view of the anode 133 showing the focus size for scanning and the focus size for warm-up. As shown in FIGS. 3 and 4, during scanning, the thermoelectrons from the filament 131 are focused on a focal point F1 having a scanning size. During the warm-up, the thermoelectrons from the filament 131 are focused on the focal point F2 having a size for warm-up. When the warm-up focus size is smaller than the scan focus size, the focus of the anode 133 may be roughened by the warm-up. Further, since the hot electrons collide with a wider range of the anode 133 as the focal spot size is larger, the anode 133 can be warmed faster as the focal spot size is larger when the heat amount per unit area is the same. Therefore, the warm-up focus F2 is set to a size larger than the scan focus F1 in order to warm the anode 133 quickly while preventing the focus from being rough due to warm-up. The size of the focus F2 for warm-up is set to a size that can increase the temperature of the anode 133 without causing the focus of the anode 133 to be rough.

  FIG. 5 is a front view of the anode 133 showing the focus position for scanning and the focus position for warm-up. FIG. 6 is a side view of the anode 133 showing the focus position for scanning and the focus position for warm-up. As shown in FIGS. 5 and 6, during scanning, the thermoelectrons from the filament 131 are focused at the position of the focal point F1 for scanning. During the warm-up, the thermoelectrons from the filament 131 are focused on the position of the warm-up focal point F2. When the position of the focus F2 for warm-up overlaps the position of the focus F1 for scanning, there is a possibility that the overlapping portion of the anode 133 is rough. Therefore, the position of the focus F1 and the position of the focus F2 are preferably set so that the position of the focus F1 for scanning and the position of the focus F2 for warm-up do not overlap. The position of the focal point F1 and the position of the focal point F2 are set on the same rotation radius of the anode 133. The position of the focal point F2 is preferably set outside the rotational radius from the position of the focal point F1 in order to suppress wear of the anode 133 portion on the focal point F2.

  Hereinafter, an operation example of the X-ray computed tomography apparatus according to Embodiment 1 will be described with reference to FIG.

  FIG. 7 is a diagram illustrating a timing chart of the heating current and the tube voltage regarding the switching of the focus size or the focus position according to the first embodiment. The upper graph in FIG. 7 shows the time series of the filament heating current, and the lower graph in FIG. 7 shows the time series of the tube voltage. The vertical axis of the upper graph in FIG. 7 is defined by the filament heating current [mA], and the horizontal axis is defined by time. The vertical axis of the lower graph in FIG. 7 is defined by tube voltage [kV], and the horizontal axis is defined by time. Note that it is possible to arbitrarily select whether to switch the focus size or the focus position via the input circuit 57 or the like.

  As shown in FIG. 7, when a warm-up start instruction is given by the user via the input circuit 57 (t 0), the gantry control circuit 25 uses the tube voltage control circuit 41 to warm up the X-ray tube 13. The tube current control circuit 43 and the regulator control circuit 45 are controlled. Specifically, the gantry control circuit 25 supplies a warm-up signal to the regulator control circuit 45. The controller control circuit 45 that has received the warm-up signal reads the focus voltage value corresponding to the size of the focus F2 for warm-up from the memory or the like in the case of changing the focus size, and converts the focus voltage value to the read focus voltage value. A corresponding electric field is applied to the regulator 137. In the case of changing the focal position, the controller control circuit 45 reads a deflection voltage value corresponding to the position of the warm-up focus F2 from a memory or the like, and supplies an electric field corresponding to the read deflection voltage value to the regulator 137. Apply. Further, the gantry control circuit 25 controls the tube voltage control circuit 41 and the tube current control circuit 43 synchronously so that the temperature of the anode 133 of the X-ray tube 13 rises gently. The gantry control circuit 25 controls the tube current control circuit 43 so as to gradually increase the filament heating current value from 0 to the set tube current value A1 in order to gradually increase the temperature of the anode 133 of the X-ray tube 13. The tube voltage control circuit 41 is controlled so that the tube voltage value is gradually increased from 0 to the set tube voltage value V1. As a result, the X-ray tube 13 can be warmed up by the warm-up focus F2. Here, gradual is longer than the time when the tube current detection value reaches the set tube current value A1 when the set value of the feedback control by the tube current control circuit 43 is initially set to the set tube current value A1. A time longer than the time when the tube voltage detection value reaches the set tube voltage value V1 when time is taken or when the set value of the feedback control by the tube voltage control circuit 41 is initially set to the set tube voltage value V1. It means that.

  For example, from the warm-up start time t0 to the end time t1, the tube current control circuit 43 linearly increases the feedback control set value from the initial value to the set tube current value A1, and similarly, the tube voltage control circuit 41 The feedback control set value may be increased linearly from the initial value to the set tube voltage value V1. The warm-up period is preferably set in advance via the input circuit 57 or the like. Alternatively, the tube current control circuit 43 and the tube voltage control circuit 41 may end the warm-up when the amount of heat applied to the X-ray tube 13 reaches a predetermined threshold. The amount of heat applied to the X-ray tube 13 may be calculated based on, for example, a tube voltage detection value from the tube voltage detector 37 and a tube current detection value from the tube current detector 39, or an X-ray You may measure with the calorimeter provided in the tube 13.

  The way of increasing the feedback control set value is not limited to linear increase. For example, the tube voltage control circuit 41 increases the feedback control set value from the initial value to the set tube voltage value V1, and the tube current control circuit 43 increases the feedback control set value from the initial value to the set tube current value A1 step by step. Thus, the temperature of the anode 133 of the X-ray tube 13 may be gradually increased. Specifically, the tube voltage control circuit 41 waits for the set time to elapse at each feedback set value from the initial set value to the set tube voltage value V1. Every time the set time elapses, the tube voltage control circuit 41 increases the feedback control set value by one step. When the set tube voltage value V1 is set to the feedback control set value, the tube voltage control circuit 41 stops the high voltage generation circuit 33 when the set time has elapsed. Similarly, the tube current control circuit 43 waits for the set time to elapse at each feedback control set value from the initial set value to the set tube current value A1. Every time the set time elapses, the tube current control circuit 43 raises the feedback control set value by one step. Then, when the set tube current value A1 is set to the feedback control set value, the tube current control circuit 43 stops the filament heating circuit 35 when the set time has elapsed.

  In the above description, the feedback control set value is increased every time the set time elapses. However, this embodiment is not limited to this. For example, the tube voltage control circuit 41 and the tube current control circuit 43 monitor the amount of heat applied to the X-ray tube 13 at each feedback control set value, and when the amount of heat exceeds a threshold value, the feedback control set value May be raised.

  The timing of raising the feedback control set value between the heating current and the tube voltage is not particularly limited. That is, in the present embodiment, the feedback control set value of the heating current and the tube voltage may be increased at the same timing or may be alternately performed. By alternately raising the feedback control set value, the temperature of the X-ray tube 13 can be raised more gently, and a rapid temperature rise can be prevented.

  The adjuster control circuit 45 may control the adjuster 137 to oscillate the position of the warm-up focus with respect to the radial direction of the anode 133. By oscillating the position of the warm-up focus with respect to the radial direction of the anode 133, the hot electrons collide with a wide area of the anode 133, so that the anode 133 can be warmed more quickly.

  Even during warm-up, X-rays are generated by the impact of thermoelectrons on the anode 133. For this reason, it is preferable that the aperture blades of the front collimator 19 are closed during warm-up. By closing the diaphragm blade, the X-ray generated from the anode 133 is prevented from leaking to the outside, the X-ray detector 15 is prevented from being deteriorated, and a medical worker such as a user or a subject such as a patient Unnecessary exposure can be prevented.

  When the generation of the high voltage by the high voltage generation circuit 33 and the generation of the heating power by the filament heating circuit 35 are completed, the warm-up is completed (t1). The warm-up is typically performed over a period of about 5 minutes. In an emergency, it takes about 1-2 minutes. When the warm-up is completed, the subject is positioned. From the end of warm-up (time t1) to the start of scanning (time t2), application of high voltage and supply of heating current are stopped.

  Then, triggered by the input of a scan start instruction by the user via the input circuit 57 (t2), the gantry control circuit 25 controls the high voltage generator 17, the rotation drive device 23, and the data collection circuit 27. Start scanning. At this time, the gantry control circuit 25 supplies the scan signal to the regulator control circuit 45. When the focus size is changed, the controller control circuit 45 that has received the scan signal reads the focus voltage value corresponding to the size of the focus F1 for scanning from the memory or the like, and corresponds to the read focus voltage value. The regulator 137 is controlled so that an electric field is applied. Thereby, the size of the focus of the thermoelectrons is switched to the size of the focus F1 for scanning. In the case of changing the focal position, the controller control circuit 45 reads a deflection voltage value corresponding to the position of the scanning focus F1 from a memory or the like, and applies an electric field corresponding to the read deflection voltage value to the regulator 137. To do. Thereby, the position of the focus of the thermoelectrons is switched to the position of the focus F1 for scanning.

  The gantry control circuit 25 controls the rotation driving device 23 to rotate the rotating frame. When the angular velocity of the rotating frame reaches a set value, the gantry control circuit 25 controls the high voltage generator 17 and the data collecting circuit 27 to control the X-ray. Repeated exposure and data collection. At this time, the gantry control circuit 25 controls the tube voltage control circuit 41 so that a high voltage corresponding to the set tube voltage value V1 is applied to the X-ray tube 13 by the high voltage generation circuit 33, and the set tube current value. The tube current control circuit 43 is controlled so that the heating current corresponding to A1 is supplied to the filament 131 by the filament heating circuit. X-rays are exposed by applying a high voltage and supplying a heating current. In this embodiment, since warm-up is performed before the scan, a high voltage corresponding to the set tube voltage value V1 is applied to the X-ray tube 13 immediately after the start of the scan, and the heating current of the set tube current value A1. Even if the X-ray tube 13 is supplied, the X-ray tube 13 can continue to emit X-rays without generating discharge.

  X-rays exposed from the X-ray tube 13 pass through the subject and are detected by the X-ray detector 15. The data collection circuit 27 collects raw data corresponding to the X-ray intensity detected by the X-ray detector 15 for each view. The collected raw data is transmitted to the console 50. The image reconstruction device 51 reconstructs a CT image related to the subject based on the raw data from the gantry device 10. The reconstructed CT image is displayed by the display circuit 55.

  When the predetermined time has elapsed (t3), the gantry control circuit 25 controls the high voltage generator 17, the rotation drive device 23, and the data collection circuit 27 to end the scan.

  This completes the description of the operation example of the X-ray computed tomography apparatus according to Embodiment 1.

  In the above description, it is assumed that the heating current value is increased to the set value A1 and the tube voltage value is increased to the set value V1 in the warm-up. However, this embodiment is not limited to this. For example, in the warm-up, the heating current value may not be raised to the set value A1, or may be raised to a value larger than the set value A1. Similarly, in warm-up, the tube voltage value may not be raised to the set value V1, or may be raised to a value larger than the set value V1.

  In the above, it is assumed that the size of the focus for scanning is one. However, this embodiment is not limited to this. For example, a plurality of scan focus sizes may be set. For example, a large focus having a relatively large size and a small focus having a relatively small size may be set as the focus for scanning. Even in this case, the size of the focus for warm-up is set larger than the size of the large focus for scanning.

  In the above description, either the focus size or the focus position is switched. However, both the focus size and the focus position may be switched.

  As described above, the X-ray computed tomography apparatus according to the first embodiment selectively switches at least one of the focus size and the focus position between scanning and warm-up by using the focus size and focus position variable function. By making the focal spot size and focal position in the warm-up different from the focal spot size and focal position in the scan, the roughness of the surface of the anode 133 is reduced compared to the case where the focal spot size and focal position are the same in the scanning and the warm-up. can do. Further, by setting a focus size and a focus position specialized for warm-up, warm-up can be performed more efficiently. Further, since the number of filaments 131 can be reduced as compared with Example 2 described later, the circuit scale, cost, etc. associated with the increase in filaments 131 can be reduced.

  Thus, according to the present embodiment, it is possible to suppress deterioration of the X-ray tube due to warm-up.

(Example 2)
In the first embodiment, the adjuster 137 switches between the scan focus size and focus position and the warm-up focus size and focus position. In the second embodiment, it is assumed that the X-ray tube 13 accommodates a scanning filament and a warm-up filament. Hereinafter, an X-ray computed tomography apparatus according to Embodiment 2 will be described. In the following description, components having substantially the same functions as those in the first embodiment are denoted by the same reference numerals, and redundant description is provided only when necessary.

  FIG. 8 is a diagram illustrating a configuration of the X-ray tube 13 and the high voltage generator 17 according to the second embodiment. As shown in FIG. 8, the X-ray tube 13 according to the second embodiment includes a scanning filament 131-1 and a warm-up filament 131-2. The scanning filament 131-1 has a form capable of forming a scanning focus size, and the warm-up filament 131-2 has a form capable of forming a warm-up focus size. Similar to the first embodiment, the warm-up focus size is set to be larger than the scan focus size.

  The high voltage generator 17 according to the second embodiment includes a power supply circuit 31, a high voltage generation circuit 33, a filament heating circuit 35, a tube voltage detector 37, a tube current detector 38, a tube voltage control circuit 41, and a tube current control circuit 43. And a switch 47. The switch 47 connects the filament heating circuit 35 so as to be switchable between the scanning filament 131-1 and the warm-up filament 131-2. The switch 47 selectively connects the filament heating circuit 35 to the scanning filament 131-1 or the warm-up filament 131-2 in accordance with the control by the gantry control circuit 25. Specifically, when the scan signal is supplied from the gantry control circuit 25, the switch 47 connects the filament heating circuit 35 to the scanning filament 131-1, and the warm-up signal is supplied from the gantry control circuit 25. In this case, it is connected to the filament 131-2 for warm-up.

  FIG. 9 is a front view of the anode 133 showing the focus size for scanning and the focus size for warm-up according to the second embodiment. FIG. 10 is a side view of the anode 133 showing the focus size for scanning and the focus size for warm-up according to the second embodiment. As shown in FIGS. 9 and 10, the thermoelectrons from the scanning filament 131-1 are focused on a focal point F 1 having a scanning size. Thermoelectrons from the warm-up filament 131-2 are focused on a focal point F2 having a warm-up size. The size of the warm-up focus F2 is set to be larger than the size of the scan focus F1 in order to warm the anode 133 in a wide range. The size of the warm-up focus F2 is set to a size that can increase the temperature of the anode 133. For this reason, the warm-up filament 131-2 is preferably designed to be larger than the scanning filament 131-1.

  The scanning filament 131-1 and the warm-up filament 131-2 are arranged so that the scanning focus F1 of the anode 133 is included in the trajectory T2 of the warm-up focus F2. By including the scan focus F1 in the trajectory T2 of the warm-up focus F2, the portion of the anode 133 used in the scan can be reliably warmed in the warm-up.

  Recoil electrons fly from the anode 133 due to the collision of thermoelectrons or the emission of X-rays from the anode 133. When the filament 131-1 or the filament 131-2 is disposed at a position close to the anode 133, the recoil electrons collide with the filament 131-1 or the filament 131-2, so that the filament 131-1 or the filament 131-2 is There is a risk of deterioration. Therefore, the filament 131-1 and the filament 131-2 are preferably arranged at positions that are not affected by recoil electrons flying from the anode 133. For example, the filament 131-1 and the filament 131-2 are preferably arranged at positions separated from the anode 133 such that recoil electrons flying from the anode 133 do not collide.

  The distance between the filament 131-1 and the anode 133 and the distance between the filament 131-2 and the anode 133 can be arbitrarily designed according to the size of the focus F1 for scanning and the size of the focus F2 for warm-up. is there. At this time, the distance between the filament 131-1 and the anode 133 and the distance between the filament 131-2 and the anode 133 may be the same or different.

  Hereinafter, an operation example of the X-ray computed tomography apparatus according to the second embodiment will be described with reference to FIG.

  FIG. 11 is a timing chart of the heating current and tube voltage related to switching between the scanning filament 131-1 and the warm-up filament 131-2 according to the second embodiment. The upper graph in FIG. 11 shows the time series of the heating current to the filament 131-2 for warm-up, and the middle graph in FIG. 11 shows the time series of the heating current to the filament 131-1 for scanning. The lower graph of 11 shows the time series of the tube voltage. The vertical axis of the upper and middle graphs in FIG. 11 is defined by the filament heating current [mA], and the horizontal axis is defined by time. The vertical axis of the lower graph in FIG. 11 is defined by tube voltage [kV], and the horizontal axis is defined by time.

  As shown in FIG. 11, when a warm-up start instruction is given by the user via the input circuit 57 (t0), the gantry control circuit 25 uses the tube voltage control circuit 41 to warm up the X-ray tube 13. The tube current control circuit 43 and the switch 47 are controlled. Specifically, the gantry control circuit 25 supplies a warm-up signal to the switch 47. Upon receiving the warm-up signal, the switch 47 connects the filament heating circuit 35 to the warm-up filament 131-2. Further, the gantry control circuit 25 controls the tube voltage control circuit 41 and the tube current control circuit 43 synchronously so that the temperature of the anode 133 of the X-ray tube 13 rises gently. Accordingly, the X-ray tube 13 can be warmed up using the warm-up filament 131-2, and the consumption of the scan filament 131-1 due to the combined use of warm-up and scanning is suppressed. be able to. In addition, since the control aspect of the heating current and tube voltage in a warm-up is the same as Example 1, description is abbreviate | omitted.

  When the generation of the high voltage by the high voltage generation circuit 33 and the generation of the heating power by the filament heating circuit 35 are completed, the warm-up is completed (t1). When the warm-up is completed, the subject is positioned.

  Then, triggered by the input of a scan start instruction by the user via the input circuit 57 (t2), the gantry control circuit 25 controls the high voltage generator 17, the rotation drive device 23, and the data collection circuit 27. Start scanning. At this time, the gantry control circuit 25 supplies a scan signal to the switch 47. The switch 47 that receives the supply of the scan signal connects the filament heating circuit 35 to the scanning filament 121-1. At this time, the gantry control circuit 25 controls the rotation driving device 23 to rotate the rotating frame, and controls the high voltage generator 17 and the data collecting circuit 27 when the angular velocity of the rotating frame reaches a set value. Repeat X-ray exposure and data collection. At this time, the gantry control circuit 25 controls the tube voltage control circuit 41 so that a high voltage corresponding to the set tube voltage value V1 is applied to the X-ray tube 13 by the high voltage generation circuit 33, and the set tube current value. The tube current control circuit 43 is controlled so that the heating current corresponding to A1 is supplied to the filament 131 by the filament heating circuit. In this embodiment, since warm-up is performed before the scan, a high voltage of the set tube voltage value V1 is applied to the X-ray tube 13 immediately after the start of the scan to supply a heating current of the set tube current value A1. Even so, the X-ray tube 13 can continue to irradiate X-rays without the occurrence of discharge.

  X-rays exposed from the X-ray tube 13 pass through the subject and are detected by the X-ray detector 15. The data collection circuit 27 collects raw data corresponding to the X-ray intensity detected by the X-ray detector 15 for each view. The collected raw data is transmitted to the console 50. The image reconstruction device 51 reconstructs a CT image related to the subject based on the raw data from the gantry device 10. The reconstructed CT image is displayed by the display circuit 55.

  When the predetermined time has elapsed (t3), the gantry control circuit 25 controls the high voltage generator 17, the rotation drive device 23, and the data collection circuit 27 to end the scan.

  This is the end of the description of the operation example of the X-ray computed tomography apparatus according to Embodiment 2.

  In the above description, the X-ray computed tomography apparatus according to the second embodiment does not include the adjuster 137 and the adjuster control circuit 45. However, Example 2 is not limited to this. That is, the X-ray tube 13 according to the second embodiment may include the adjuster 137, and the high voltage generator 17 may include the adjuster control circuit 45. In this case, the regulator control circuit 45 controls the regulator 137 during the warm-up, and vibrates the position of the focal point at the anode 133 due to the thermal electrons from the warm-up filament 131-2 in the radial direction of the anode 133. May be. By vibrating the focal point with respect to the radial direction of the anode 133, the hot electrons collide with a wide range of the anode 133, so that the anode 133 can be warmed more quickly.

  In the above description, it is assumed that the number of scanning filaments 131-1 is one. However, this embodiment is not limited to this. For example, a plurality of scanning filaments 131-1 may be provided. For example, as the scanning filament 131-1, a large focal filament having a relatively large focal size and a small focal filament having a relatively small focal size may be provided. Even in this case, the focal size of the warm-up filament 131-2 is set larger than the focal size of the scanning large focal filament.

  As described above, the X-ray computed tomography apparatus according to the second embodiment includes the X-ray tube 13 having the scanning filament 131-1 and the warm-up filament 131-2. By using different filaments for scanning and warm-up, warm-up can be performed without affecting the life of the filament 131-1 such as scanning. Therefore, the consumption of the scanning filament 131-1 can be reduced. By optimizing the size of the filament 131-2 for warm-up, unnecessary deterioration of the anode 133 can be prevented. By providing a filament of a size specialized for warm-up, warm-up can be performed more efficiently. Further, as compared with the first embodiment, the control for changing the focal spot size can be omitted.

  Thus, according to the present embodiment, it is possible to suppress deterioration of the X-ray tube due to warm-up.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Mount apparatus, 11 ... Rotating frame, 13 ... X-ray tube, 15 ... X-ray detector, 17 ... High voltage generator, 19 ... Pre-collimator, 21 ... Top plate, 23 ... Rotary drive device, 25 ... Mounting control circuit, 27... Data collection circuit, 50... Console, 51... Image reconstruction circuit, 53... Image processing circuit, 55. DESCRIPTION OF SYMBOLS ... Power supply circuit, 33 ... High voltage generation circuit, 35 ... Filament heating circuit, 37 ... Tube voltage detector, 39 ... Tube current detector, 41 ... Tube voltage control circuit, 43 ... Tube current control circuit, 45 ... Concentrator control Circuit 131 131 Filament 133 Anode 135 Rotor 137 Regulator 511 Data storage circuit 513 Pre-processing unit 515 Reconfiguration processing unit

Claims (13)

X having a cathode for generating thermoelectrons, an anode for generating X-rays upon receiving thermoelectrons from the cathode, and a regulator for applying an electric or magnetic field for focusing or deflecting the thermoelectrons from the cathode A tube,
An X-ray detector for detecting X-rays generated from the anode;
A data collection unit for collecting data according to the X-rays detected by the X-ray detector;
An image generation unit for generating an image based on the collected data;
A controller for controlling the regulator to switch between scanning and warming up at least one of the size and position of the focus at the anode of the thermoelectrons from the cathode;
An X-ray computed tomography apparatus comprising:   The control unit sets the size of the focus at the anode in the scan to a first size, and sets the size of the focus at the anode in the warm-up to a second size larger than the first size. The X-ray computed tomography apparatus according to claim 1, wherein the controller is controlled to   The control unit controls the adjuster to set the focal spot size to the second size with the start of the warm-up, and takes the focal spot size with the start of the scan. The x-ray computed tomography apparatus of claim 2, wherein the controller is controlled to achieve a size of one.   2. The controller according to claim 1, wherein the controller controls the adjuster to oscillate a position of the focal point of the thermoelectrons from the cathode at the anode in the rotation radius direction during the warm-up. X-ray computed tomography apparatus.   The controller controls the adjuster to move the position of the focal point of the thermoelectrons from the cathode at the anode during the warm-up to a position different from that at the time of scanning in the rotational radius direction of the anode. The X-ray computed tomography apparatus according to claim 1, which is controlled. A first cathode that is used for scanning and generates thermoelectrons, a second cathode that is used for warming up and generates thermoelectrons, and receives the thermoelectrons from the first cathode or the second cathode and receives X An X-ray tube having an anode for generating a line;
An X-ray detector for detecting X-rays generated from the anode;
A data collection unit for collecting data according to the X-rays detected by the X-ray detector;
An image generation unit for generating an image based on the collected data;
An X-ray computed tomography apparatus comprising: A switch for switching a current supply destination between the first cathode and the second cathode;
A controller that controls the switch to supply current to the first cathode during the scan and to supply current to the second cathode during the warm-up;
The X-ray computed tomography apparatus according to claim 6.   The control unit controls the switch to supply current to the second cathode at the start of the warm-up, and supplies current to the second cathode at the end of the warm-up. The X-ray computed tomography apparatus according to claim 7, wherein the switch is controlled so as not to be supplied, and the switch is controlled so as to supply a current to the first cathode when the scan is started.   The first cathode and the second cathode so that the focus of the thermoelectrons from the first cathode at the anode is included in the second trajectory of the focus of the thermoelectrons from the second cathode at the anode. The X-ray computed tomography apparatus according to claim 6, wherein a cathode is disposed.   The X-ray computed tomography apparatus according to claim 6, wherein the second cathode is disposed at a position where the second cathode is not affected by recoil electrons caused by thermal electron collision with the anode.   The X-ray computed tomography apparatus according to claim 6, wherein the second cathode includes a metal having a thin line shape or a plate shape. A regulator for applying an electric or magnetic field for focusing the thermionic electrons from the first or second cathode;
The control unit controls the adjuster so as to vibrate the position of the focal point at the anode by the thermal electrons from the second cathode in the warm-up with respect to the rotational radius direction of the anode.
The X-ray computed tomography apparatus according to claim 6. A first cathode used for scanning and generating thermionic electrons;
A second cathode used for warm-up and generating thermionic electrons;
An anode for generating X-rays upon receiving thermoelectrons from the first cathode or the second cathode;
An X-ray tube device comprising: