JP2019092585A - X-ray CT apparatus and X-ray generation system - Google Patents

Abstract

To change a focal position without changing the quality of an irradiated X-ray.SOLUTION: An X-ray CT apparatus includes a negative pole, a positive pole, a first thermal electron adjusting part, a second thermal electron adjusting part, and a control part. The negative pole generates a thermal electron. The positive pole receives the thermal electron irradiated from the negative pole and generates an X-ray. The first thermal electron adjusting part adjusts the track of the thermal electron. The second thermal electron adjusting part further adjusts the track of the thermal electron adjusted by the first thermal electron adjusting part. The control part controls a focal position of the thermal electron in the positive pole while keeping an irradiation angle of the thermal electron to the positive pole constant by controlling the first thermal electron adjusting part and the second thermal electron adjusting part.SELECTED DRAWING: Figure 2

Description

  Embodiments of the present invention relate to an X-ray CT apparatus and an X-ray generation system.

  The X-ray imaging is performed by an X-ray imaging apparatus provided with an X-ray tube apparatus generating X-rays and an X-ray detector facing each other across an imaging target such as a patient. In addition, there is known a technique called FFS (flying focal spot) for increasing spatial resolution by rapidly changing a focal position, which is an X-ray generation position on an anode in an X-ray tube apparatus. In this case, as the focal position changes, the path through which the generated X-rays pass through the anode changes, and the quality of the X-rays changes unintentionally, resulting in a decrease in the image quality to be photographed. there's a possibility that. Therefore, it is desirable that the line quality not change according to the change of the focal position.

JP, 2011-229906, A JP, 2015-208601, A

  The problem to be solved by the present invention is to make it possible to change the focal position without changing the radiation quality of the irradiated X-ray.

  The X-ray CT apparatus according to the embodiment includes a cathode, an anode, a first thermoelectron adjustment unit, a second thermoelectron adjustment unit, and a control unit. The cathode generates thermoelectrons. The anode receives thermal electrons emitted from the cathode to generate X-rays. The first thermoelectron adjustment unit adjusts the trajectory of the thermoelectrons. The second thermal electron adjustment unit further adjusts the trajectory of the thermal electrons adjusted by the first thermal electron adjustment unit. The control unit controls the first thermoelectron adjustment unit and the second thermoelectron adjustment unit to keep the irradiation angle of the thermoelectrons to the anode constant, while the heat energy at the anode is maintained. Control the focus position of the electron.

FIG. 1 is a block diagram showing an example of the arrangement of an X-ray CT apparatus according to the first embodiment. FIG. 2 is a diagram (1) illustrating an exemplary configuration of an X-ray tube. FIG. 3 is a perspective view showing only the thermoelectronic adjustment mechanism of FIG. FIG. 4 is a view showing a configuration example of an X-ray high voltage apparatus. FIG. 5A is a diagram (1) illustrating an example of a control method of the adjustment amount of the thermoelectron adjustment mechanism. FIG. 5B is a diagram (2) illustrating an example of a control method of the adjustment amount of the thermoelectron adjustment mechanism. FIG. 6A is a diagram (1) illustrating an example of adjustment of the trajectory of thermions by the thermionic adjustment mechanism. FIG. 6B is a diagram (2) illustrating an example of adjustment of the trajectories of thermions by the thermionic adjustment mechanism. FIG. 6C is a diagram (3) illustrating an example of adjustment of the trajectories of thermions by the thermionic adjustment mechanism. FIG. 7A is a diagram (1) illustrating an example of adjustment of the trajectories of thermoelectrons by a pair of electrodes for comparison. FIG. 7B is a diagram (2) illustrating an example of adjustment of the trajectories of thermoelectrons by a pair of electrodes for comparison. FIG. 7C is a diagram (3) illustrating an example of adjustment of the trajectories of thermoelectrons by a pair of electrodes for comparison. FIG. 8 is a flow chart showing an example of processing of CT imaging by FFS. FIG. 9 is a diagram showing an example of control timing of CT imaging by FFS. FIG. 10 is a diagram (1) illustrating another configuration example of the thermal electronic adjustment mechanism. FIG. 11A is a diagram (4) illustrating an example of adjustment of the trajectories of thermoelectrons by the thermoelectron adjustment mechanism. FIG. 11B is a diagram (5) illustrating an example of adjustment of the trajectories of thermions by the thermionic adjustment mechanism. FIG. 11C is a diagram (6) illustrating an example of adjustment of the trajectories of thermions by the thermionic adjustment mechanism. FIG. 12 is a diagram (2) illustrating another configuration example of the thermal electronic adjustment mechanism. FIG. 13 is a diagram (1) illustrating another configuration example of the X-ray tube. FIG. 14 is a diagram (2) showing a configuration example of an X-ray tube. FIG. 15 is a diagram (2) showing another configuration example of the X-ray tube.

  Hereinafter, embodiments of the X-ray CT apparatus and the X-ray generation system will be described with reference to the drawings. The embodiment is not limited to the following contents. In addition, the contents described in one embodiment or modification are applied to other embodiments or modifications in the same manner in principle.

First Embodiment
The configuration of the X-ray CT apparatus 1 according to the first embodiment will be described with reference to FIG. The X-ray generation system is a portion used for generating X-rays in the X-ray CT apparatus 1 and is a part of the configuration of the X-ray CT apparatus 1. FIG. 1 is a block diagram showing an example of the arrangement of an X-ray CT apparatus 1 according to the first embodiment. As shown in FIG. 1, the X-ray CT apparatus 1 has a gantry device 10, a couch device 30, and a console device 40. In FIG. 1, the rotation axis of the rotary frame 16 in the non-tilted state of the gantry device 10 or the longitudinal direction of the top plate 33 of the bed device 30 is taken as the Z-axis direction. Further, an axial direction orthogonal to the Z-axis direction and horizontal to the floor surface is taken as an X-axis direction. Further, an axial direction perpendicular to the Z-axis direction and perpendicular to the floor surface is taken as a Y-axis direction.

  The gantry device 10 includes an X-ray tube 11, an X-ray detector 15, a rotating frame 16, an X-ray high voltage device 17, a control device 18, a wedge 19, a collimator 20, and a data acquisition circuit 21. Have.

  The X-ray tube 11 is a vacuum tube having a cathode (filament) generating thermal electrons and an anode (target) generating an X-ray under collision of thermal electrons. The X-ray tube 11 irradiates thermal electrons from the cathode to the anode by the high voltage supplied from the X-ray high voltage device 17. The X-ray high-voltage device 17 not only generates high voltage, but also supplies power to the filament, supplies driving power to the rotary anode (in the case of the rotary anode), drives the thermoelectron adjustment mechanism described later, etc. Do also. Details will be described later.

  FIG. 2 is a view showing a configuration example of the X-ray tube 11, and shows an example of a rotary anode. In FIG. 2, the X-ray tube 11 includes a housing 111, a cathode 113, a first thermoelectron adjustment mechanism 114, a second thermoelectron adjustment mechanism 115, an anode 116, and a rotation shaft 117. There is. The housing 111 is made of, for example, metal, and has an X-ray window 112 through which internally generated X-rays pass. The cathode 113 generates thermoelectrons. Thermionic electrons are electrons excited by heat generated by the current flowing through the filament and ejected from the filament or the heated member.

  The anode 116 receives the collision of thermal electrons emitted from the cathode 113 to generate X-rays. Specifically, a large potential difference is provided between the cathode 113 and the anode 116. For example, a potential difference is provided between the cathode 113 and the anode 116 by grounding the anode 116 and making the potential of the cathode 113 negative. Due to this potential difference, the thermoelectrons emitted from the cathode 113 are accelerated and collide with the anode 116 to generate X-rays. Further, the anode 116 is a rotating body rotated by the rotating shaft 117, and the outer periphery is circular when viewed from the axial direction of the rotating shaft 117. The anode 116 has an umbrella-like shape, and the tip end side of the umbrella faces the cathode 113 side. The side of the anode 116 facing the cathode 113 is a tapered surface, and forms a surface inclined toward the X-ray window 112 by a slight angle with respect to the cathode 113 side. The anode 116 is rotated to disperse the position where heat is generated by the collision of thermal electrons, thereby avoiding dissolution of the surface of the anode 116 due to heat generation. The rotating shaft 117 is supported by a bearing or the like (not shown) and is rotationally driven by a rotating magnetic field generated by a stator coil or the like (not shown). In the drawing, the trajectories of thermal electrons (shown by alternate long and short dashed lines) from the cathode 113 to the anode 116 are drawn parallel to the rotation axis 117 of the anode 116, but the invention is not limited thereto.

  The first thermoelectron adjustment mechanism 114 and the second thermoelectron adjustment mechanism 115 are provided along the orbit of the thermoelectrons between the cathode 113 and the anode 116 so as to sandwich the orbit, and the cathode 113 is formed by the electric field. Changes the orbit of thermionic electrons emitted from. The first thermal electronic adjustment mechanism 114 includes an adjustment pole 114 a and an adjustment pole 114 b. The thermoelectron adjustment mechanism 115 includes an adjustment pole 115 a and an adjustment pole 115 b. When an electric field is used to adjust the trajectory, the adjustment electrodes 114a, 114b, 115a, and 115b are, for example, flat electrodes, different potentials are applied negative to the potential of the cathode 113, and have negative charges. The repulsive force acting on the thermoelectrons changes the orbit of the thermoelectrons to the side where the potential is relatively high.

  FIG. 3 is a perspective view showing only the thermoelectronic adjustment mechanism of FIG. That is, the adjustment pole 114 a and the adjustment pole 114 b of the first thermoelectron adjustment mechanism 114 face each other at a distance in the Y-axis direction. Further, the adjustment pole 115 a and the adjustment pole 115 b of the second thermoelectron adjustment mechanism 115 face each other at a distance in the Y-axis direction.

  FIG. 4 is a view showing an example of the arrangement of the X-ray high voltage apparatus 17. As shown in FIG. In FIG. 4, the X-ray high voltage device 17 includes an X-ray high voltage supply circuit 171, a filament power supply circuit 172, an anode rotation drive power supply circuit 173, and a thermionic adjustment mechanism drive circuit 174. The X-ray high voltage supply circuit 171 generates and supplies a high voltage applied between the cathode 113 and the anode 116 of the X-ray tube 11. The X-ray high voltage supply circuit 171 has an electric circuit such as a transformer and a rectifier, and generates a high voltage to be applied to the X-ray tube 11 and X emitted by the X-ray tube 11. And X-ray control circuit for controlling the output voltage according to the line. The high voltage generation circuit may be a transformer type or an inverter type.

  The filament power supply circuit 172 supplies power to the filament of the X-ray tube 11. The anode rotation drive power supply circuit 173 supplies power to rotationally drive the anode 116. The thermionic adjustment mechanism drive circuit 174 controls an electric field acting on the orbit of the thermal electrons by a voltage or the like supplied to the thermionic adjustment mechanisms 114 and 115. The X-ray high voltage device 17 may be provided on the rotating frame 16 or may be provided on a fixed frame (not shown). Also, the X-ray high voltage apparatus 17 has been described as a configuration example including the X-ray high voltage supply circuit 171, the filament power supply circuit 172, the anode rotation drive power supply circuit 173, and the thermal electronic adjustment mechanism drive circuit 174 A part may be provided as another device.

FIG. 5A is a diagram showing an example of a control method of the adjustment amount of the thermionic adjustment mechanisms 114 and 115, and uses data of a table format. The data in the form of a table is held in a memory 41 or the like described later. In FIG. 5A, the first adjustment amount for the first thermoelectron adjustment mechanism 114 and the second adjustment amount for the second thermoelectron adjustment mechanism 115 are stored in correspondence with the focus position index representing the focus position. Be done. The focus position index is, for example, a numerical value indicating a distance in a different direction from the reference position on the anode 116, or a symbol such as "P ₀ ", "P ₁ ", or "P ₂ ". The first adjustment amount and the second adjustment amount are, for example, voltage values (including the polarity corresponding to the adjustment direction) applied to the adjustment electrodes 114 a to 114 d and 115 a to 115 d when an electric field is used.

  FIG. 5B is a diagram showing an example of another control method of the adjustment amount of the thermoelectron adjustment mechanism 114, 115, which uses an equation. In FIG. 5B, the first adjustment amount for the first thermoelectron adjustment mechanism 114 is calculated by the function F1 for the focus position index. Further, the second adjustment amount for the second thermoelectron adjustment mechanism 115 is calculated by the function F2 for the focus position index. Thereby, when the focus position index is determined, the corresponding first adjustment amount and second adjustment amount can be obtained.

  6A to 6C are diagrams showing an example of adjustment of the orbits of thermions by the thermionic adjustment mechanisms 114 and 115, and show a case where an electric field is used for adjustment of the orbits. Further, the thermoelectron adjustment mechanisms 114 and 115 show the case where the adjustment poles 114a and 114b and the adjustment poles 115a and 115b opposed to each other in the Y-axis direction in the figure are provided.

FIG. 6A shows a case where the adjustment is off in both the first thermal electron adjustment mechanism 114 and the second thermal electron adjustment mechanism 115, and the orbit of the thermal electrons emitted from the cathode 113 Is not adjusted, and the anode 116 is irradiated. That is, the thermions emitted from the cathode 113 are drawn to the anode 116 to which a positive high potential difference is applied to the cathode 113, and are irradiated straight to a certain focal position P ₀ . The irradiation angle in this case is θ ₀ . The thermal electrons are irradiated to the anode 116 to generate X-rays.

FIG. 6B shows a case where the adjustment is on (ON) in both the first thermal electron adjustment mechanism 114 and the second thermal electron adjustment mechanism 115, and the thermal electron adjustment mechanism 114 in the first thermal electron adjustment mechanism 114 The upward (Y-axis positive direction) adjustment in the Y-axis direction is performed with respect to the electron orbit, and the second thermoelectron adjustment mechanism 115 downward (Y-axis negative direction) in the Y-axis direction with respect to the thermoelectron orbit. Shows the case where the adjustment of. By setting the adjustment amount appropriately in advance, the irradiation angle to the anode 116 remains unchanged as in the case of FIG. 6A, θ ₀ , and the focal position changes upward to become P ₁ . In this case, since the irradiation angle to the anode 116 does not change, the quality of X-rays generated from the anode 116 does not change. That is, the irradiation angle to the anode 116 changes the depth at which the thermoelectrons intrude from the surface of the anode 116, and there is a path for the X-ray generated inside the anode 116 to pass through the inside of the anode 116 and go out. It changes, and the line quality is affected (the longer the path distance, the longer the absorption of long wavelength components and the harder the line quality). However, when the irradiation angle does not change, the line quality becomes constant.

FIG. 6C shows a case where the adjustment is ON for both of the first thermal electron adjustment mechanism 114 and the second thermal electron adjustment mechanism 115, and the thermal electron adjustment mechanism 114 in the first thermal electron adjustment mechanism 114 The downward adjustment in the Y-axis direction is performed on the electron orbit, and the upward adjustment in the Y-axis direction is performed on the thermal electron orbit in the second thermal electron adjustment mechanism 115. By setting the adjustment amount appropriately in advance, the irradiation angle to the anode 116 remains unchanged as in the case of FIGS. 6A and 6B, θ ₀ , and the focal position changes downward to become P ₂ . Also in this case, since the irradiation angle to the anode 116 does not change, the quality of X-rays generated from the anode 116 does not change.

7A to 7C are diagrams showing an example of adjustment of the trajectories of thermions by a pair of electrodes for comparison. That is, the case where a pair of electrodes facing each other is provided between the cathode and the anode is shown. FIG. 7A shows the case where the electrode is off (OFF), and the trajectory of the thermions emitted from the cathode is not adjusted, and the anode is irradiated. That is, the thermions emitted from the cathode are drawn to the anode to which a positive high potential difference is applied to the cathode, and are irradiated straight to a certain focal position P ₀ . The irradiation angle in this case is θ ₀ . The thermal electrons are irradiated to the anode to generate X-rays.

FIG. 7B shows the case where the electrode is turned on (ON), and shows the case where upward adjustment is performed on the trajectory of the thermoelectrons by the pair of electrodes. In this case, the focal position moves upward to become P ₁ , and the irradiation angle becomes deep and becomes θ ₀₁ . FIG. 7C shows the case where the electrode is turned on (ON), and shows the case where downward adjustment is performed on the trajectory of the thermoelectrons by the pair of electrodes. In this case, the focal position moves downward to be P ₂ , and the irradiation angle becomes shallow to be θ ₀₂ . As described above, in the case of adjustment of the trajectories of thermoelectrons by a pair of electrodes, both the focal position and the irradiation angle change, and it is difficult to change only the focal position while keeping the irradiation angle constant. .

  Returning to FIG. 1, the X-ray detector 15 detects X-rays emitted from the X-ray tube 11 and having passed through the subject P, and outputs a signal corresponding to the detected X-ray dose to the data acquisition circuit 21. For example, the X-ray detector 15 includes a plurality of X-ray detection element rows in which a plurality of X-ray detection elements are arranged in the channel direction (surrounding direction) along one arc centered on the focal point of the X-ray tube 11 Have. The X-ray detector 15 has, for example, a structure in which a plurality of X-ray detection element rows in which a plurality of X-ray detection elements are arranged in the channel direction are arranged in the slice direction (row direction, row direction). The X-ray detector 15 is, for example, an indirect conversion detector having a grid, a scintillator array, and a light sensor array. The scintillator array has a plurality of scintillators. The scintillator has a scintillator crystal that outputs light of an amount of photons according to the incident X-ray dose. The grid is disposed on the X-ray incident side of the scintillator array, and has an X-ray shielding plate that absorbs scattered X-rays. The photosensor array has a function of converting it into an electrical signal according to the light quantity from the scintillator, and has, for example, a photosensor such as a photomultiplier tube (photomultiplier: PMT). The X-ray detector 15 may be a direct conversion detector having a semiconductor element that converts incident X-rays into an electric signal.

  The rotating frame 16 (support base) is an annular frame that supports the X-ray tube 11 and the X-ray detector 15 in an opposing manner and causes the control device 18 to rotate the X-ray tube 11 and the X-ray detector 15. For example, the rotating frame 16 is a casting made of aluminum. In addition to the X-ray tube 11 and the X-ray detector 15, the rotary frame 16 can further support the X-ray high voltage device 17 and the data acquisition circuit 21. Furthermore, the rotating frame 16 can further support various configurations not shown in FIG. In the following, in the gantry device 10, a portion that is rotationally moved with the rotation frame 16 and the rotation frame 16 will also be referred to as a rotation portion. Although the Rotate / Rotate-Type (third generation CT) in which the X-ray tube 11 and the X-ray detector 15 integrally rotate around the subject P has been described, the ring array is also available. There are various types such as Stationary / Rotate-Type (4th generation CT) in which a large number of X-ray detection elements are fixed and only the X-ray tube 11 rotates around the subject P. It is applicable.

  The detection data generated by the data acquisition circuit 21 is provided in the non-rotational portion of the gantry 10 by optical communication from a transmitter having a light emitting diode (LED) provided in the rotation frame 16. , To a receiver having a photodiode, and transferred to the console device 40. Here, the non-rotating portion is, for example, a fixed frame or the like that rotatably supports the rotating frame 16. In addition, the transmission method of the detection data from the rotation frame 16 to the non-rotation part of the gantry device 10 is not limited to the optical communication, but any method can be adopted as long as data transmission can be performed between the rotation part and the non-rotation part. It does not matter.

  The controller 18 includes drive mechanisms such as a motor and an actuator, and a circuit that controls this mechanism. The control device 18 receives an input signal from an input interface 43 or an input interface or the like provided in the gantry device 10, and performs operation control of the gantry device 10 and the couch device 30. For example, the control device 18 controls the rotation of the rotation frame 16, the tilt of the gantry device 10, the operation of the bed device 30 and the top 33, and the like. As an example, the control device 18 rotates the rotation frame 16 around an axis parallel to the X-axis direction according to the input tilt angle (tilt angle) information as control for tilting the gantry device 10. The control device 18 may be provided in the gantry device 10 or may be provided in the console device 40.

  The wedge 19 is a filter for adjusting the X-ray dose emitted from the X-ray tube 11. Specifically, the wedge 19 transmits and attenuates the X-rays emitted from the X-ray tube 11 so that the X-rays emitted from the X-ray tube 11 to the subject P have a predetermined distribution. Filter. For example, the wedge 19 is a wedge filter or a bow-tie filter, and is configured by processing aluminum or the like so as to have a predetermined target angle and a predetermined thickness.

  The collimator 20 is a lead plate or the like for narrowing the irradiation range of X-rays transmitted through the wedge 19 and forms a slit by a combination of a plurality of lead plates or the like. The degree of opening and the position of the collimator 20 are adjusted by a collimator adjustment circuit (not shown). Thereby, the irradiation range of the X-ray generated by the X-ray tube 11 is adjusted.

  The data acquisition circuit 21 is a DAS (Data Acquisition System). The data acquisition circuit 21 has an amplifier for amplifying the electric signal output from each X-ray detection element of the X-ray detector 15 and an A / D converter for converting the electric signal into a digital signal. , Generate detection data. The data acquisition circuit 21 is realized by, for example, a processor.

  The bed apparatus 30 is an apparatus for placing and moving the subject P to be scanned, and includes a base 31, a bed driving apparatus 32, a top 33, and a support frame 34. The base 31 is a housing that supports the support frame 34 so as to be movable in the vertical direction. The bed drive device 32 is a drive mechanism that moves the top 33 on which the subject P is placed in the direction of the long axis of the top 33, and includes a motor, an actuator, and the like. The top plate 33 provided on the upper surface of the support frame 34 is a plate on which the subject P is placed. In addition to the top 33, the bed driving device 32 may move the support frame 34 in the long axis direction of the top 33. When applied to standing position CT, a method of moving a patient support mechanism corresponding to the top 33 may be used. When performing a scan (helical scan, positioning scan, etc.) involving relative change of the positional relationship of the top 33 of the gantry device 10, relative change of the positional relationship may be performed by driving the top 33. , And may be performed by traveling of the gantry device 10 or a combination of them. When applied to a dental CT, the couch device 30 and the like become unnecessary.

  The console device 40 has a memory 41, a display 42, an input interface 43, and a processing circuit 44.

  The memory 41 is realized by, for example, a random access memory (RAM), a semiconductor memory device such as a flash memory, a hard disk, an optical disk, or the like. For example, the memory 41 stores projection data and reconstructed image data. Also, for example, the memory 41 stores a program for the circuit included in the X-ray CT apparatus 1 to realize its function. The memory 41 is used as a non-transitory storage medium by hardware. Note that the storage of projection data and reconstructed image data is not limited to the case where the memory 41 of the console device 40 performs, and a cloud server connectable to the X-ray CT device 1 via a communication network such as the Internet is an X-ray CT device It is also possible to store projection data and reconstructed image data in response to a storage request from 1).

  The display 42 displays various information. For example, the display 42 outputs a CT image generated by the processing circuit 44, a GUI (Graphical User Interface) for receiving various operations from the operator, and the like. For example, the display 42 is a liquid crystal display or a CRT (Cathode Ray Tube) display.

  The input interface 43 receives various input operations from the operator, converts the received input operations into electric signals, and outputs the electric signals to the processing circuit 44. For example, the input interface 43 receives from the operator collection conditions when collecting projection data, reconstruction conditions when reconstructing a CT image, and image processing conditions when generating a post-processed image from a CT image. . For example, the input interface 43 is realized by a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touch panel, or the like.

  The processing circuit 44 controls the overall operation of the X-ray CT apparatus 1. For example, the processing circuit 44 has a scan control function 441, an image generation function 442, a display control function 443 and a control function 444. The processing circuit 44 is realized by, for example, a processor.

  For example, the processing circuit 44 reads the program corresponding to the scan control function 441 from the memory 41 and executes it to control the X-ray CT apparatus 1 to execute a scan. Here, the scan control function 441 can execute scans in various methods such as conventional scan, helical scan, and step-and-shoot method.

  Specifically, the scan control function 441 moves the subject P into the imaging port of the gantry device 10 by controlling the bed driving device 32. The scan control function 441 controls the X-ray high voltage device 17 to supply a high voltage to the X-ray tube 11. Further, the scan control function 441 adjusts the orbit of the thermoelectrons in the X-ray tube 11, and changes the focal position without changing the irradiation angle on the anode 116, and controls so that the radiation quality is kept constant. Do. The scan control function 441 also adjusts the aperture and position of the collimator 20. Also, the scan control function 441 controls the control device 18 to rotate the rotating portion including the rotating frame 16. The scan control function 441 also causes the data acquisition circuit 21 to acquire projection data. In order to reconstruct a CT image, projection data of 360 ° around the subject P is required, and projection data of 180 ° + fan angle is also required in the half scan method. The present embodiment is applicable to any reconstruction method.

  Also, for example, the processing circuit 44 reads out and executes a program corresponding to the image generation function 442 from the memory 41, thereby performing logarithmic conversion processing, offset correction processing, and the like on detected data output from the data acquisition circuit 21. Data that has been subjected to preprocessing such as sensitivity correction processing and beam hardening correction. In some cases, data before the pre-processing (detection data) and data after the pre-processing may be collectively referred to as projection data. Also, for example, the image generation function 442 generates CT image data. Specifically, the image generation function 442 performs reconstruction processing using the filter correction back projection method, the successive approximation reconstruction method, or the like on the projection data after the pre-processing to generate CT image data. The image generation function 442 also converts CT image data into tomographic image data or three-dimensional image data of an arbitrary cross section based on an input operation received from the operator via the input interface 43.

  Also, for example, the processing circuit 44 displays a CT image on the display 42 by reading and executing a program corresponding to the display control function 443 from the memory 41. Further, for example, the processing circuit 44 reads out and executes a program corresponding to the control function 444 from the memory 41, thereby performing various functions of the processing circuit 44 based on the input operation received from the operator via the input interface 43. Control.

  Although FIG. 1 shows the case where each processing function of the scan control function 441, the image generation function 442, the display control function 443 and the control function 444 is realized by a single processing circuit 44, the embodiment is not limited thereto. It is not limited to For example, the processing circuit 44 may be configured by combining a plurality of independent processors, and each processor may execute each program to realize each processing function. In addition, each processing function of the processing circuit 44 may be realized by being appropriately distributed or integrated into a single or a plurality of processing circuits. The processing circuit 44 is not limited to being included in the console device 40, and may be included in an integrated server that collectively performs processing on detection data acquired by a plurality of medical image diagnostic devices. Although the console device 40 has been described as performing a plurality of functions in a single console, a plurality of functions may be executed by different consoles.

  The word “processor” used in the above description is, for example, a central processing unit (CPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), a programmable logic device (for example, A circuit such as a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), or a field programmable gate array (FPGA) is meant. The processor implements a function by reading and executing a program stored in the memory 41. Instead of storing the program in the memory 41, the program may be directly incorporated in the circuit of the processor. In this case, the processor implements the function by reading and executing a program embedded in the circuit. Each processor according to the present embodiment is not limited to being configured as a single circuit for each processor, and may be configured as one processor by combining a plurality of independent circuits to realize the function. Good.

  The thermal electronic adjustment mechanism 114 is an example of a first thermal electronic adjustment unit. The thermoelectron adjustment mechanism 115 is an example of a second thermoelectron adjustment unit. The X-ray high voltage device 17 and the console device 40 are an example of a control unit. The x-ray generation system comprises an x-ray tube 11, an x-ray high voltage device 17 and a processing circuit 44.

  Hereinafter, a processing example for performing CT imaging by FFS without changing the line quality will be described. Here, it is assumed that FFS (hereinafter, abbreviated as z-FFS) in which the focal position is changed in the Z-axis direction (body axis direction) is described. In z-FFS, the sampling pitch in the Z-axis direction can be equivalently halved, and spatial resolution can be improved. By changing the orbit of the thermions in the Y-axis direction in FIG. 2, the focal position in the Z-axis direction on the inclined surface of the anode 116 is changed, and the focal position in z-FFS is changed.

  FIG. 8 is a flow chart showing an example of processing of CT imaging by FFS. In FIG. 8, at the time of CT imaging by the X-ray CT apparatus 1, the scan control function 441 of the console device 40 receives various designations including the fact that it is a scan by FFS via the input interface 43 (step S11). The various designations include information such as patient information (patient ID, patient name, date of birth, age, weight, gender, etc.) and examination site. Patient information may be acquired from an examination reservation list registered by an examination reservation system (not shown). In an emergency, it is possible to shift to the examination by omitting the input of patient information.

  Next, the scan control function 441 of the processing circuit 44 of the console device 40 executes a scan by FFS (step S12). That is, the scan control function 441 performs control of the bed driving device 32, control of the X-ray high voltage device 17, adjustment of the collimator 20, control of the rotation frame 16, and control of the data acquisition circuit 21 to execute scanning. At this time, the scan control function 441 controls the thermionic adjustment mechanisms 114 and 115 of the X-ray tube 11 by the thermionic adjustment mechanism drive circuit 174 of the X-ray high voltage device 17 to switch the focal position for each view, for example. Run a scan A view is a unit for shooting at each angle of the rotating frame 16. The scan control function 441 calculates the adjustment amount from the focus position index and the table (FIG. 5A) in which the adjustment amounts corresponding to the two focus positions used for the FFS are associated with the focus position index and the adjustment amount. Control the voltage supplied to the thermionic adjustment mechanism 114, 115).

FIG. 9 is a diagram showing an example of control timing of CT imaging by FFS. In the odd-numbered views v 001, v 003, v 005,... In FIG. 9, for example, as described with reference to FIG. The adjustment (second adjustment) of the orbits of thermions by the second thermionic adjustment mechanism 115 is both off. In this case, the focal position is P ₀ and the irradiation angle is constant θ ₀ . Therefore, the line quality is constant (for example, "normal"). Also, in the even-numbered views v002, v004, ..., the adjustment (first adjustment) of the trajectory of thermions by the first thermionic adjustment mechanism 114 is upward, as described in, for example, FIG. 6B. The adjustment (second adjustment) of the trajectory of thermions by the thermionic adjustment mechanism 115 is downward. In this case, the focal position is P ₁ , the irradiation angle is constant θ ₀ , and the quality is constant. In addition, although the adjustment state in the case of FIG. 6A and FIG. 6B was used, it is not restricted to this. In addition, although the example in which the focal position is switched between the odd and even numbers of the view numbers has been described, the focal position may be switched in one view and shooting may be performed in each state.

  Next, returning to FIG. 8, the image generation function 442 performs preprocessing on the detection data output from the data acquisition circuit 21, and then performs reconstruction processing to generate CT image data (step S13). The detection data output from the data acquisition circuit 21 is associated with the first focal position and the second focal position, and in the case of reconstruction in z-FFS, the first focal position and the second focal position. The difference in position in the Z-axis direction is taken into account. That is, by switching the focal position in the Z-axis direction, the X-ray emitted from the X-ray tube 11 passes through the object P and the path in the Z-axis direction to the X-ray detector 15 increases. It is possible to improve the imaging resolution. In addition to switching to two focus positions, it is also possible to switch to three or more focus positions. In addition, CT image data is converted to tomographic image data or three-dimensional image data of an arbitrary cross section based on an input operation received from the operator.

  Next, the display control function 443 displays an image based on a CT image, tomographic image data of an arbitrary cross section, or three-dimensional image data on the display 42 (step S14).

  Steps S11 and S12 shown in FIG. 8 correspond to the scan control function 441. Steps S11 and S12 are steps in which the scan control function 441 is realized as the processing circuit 44 reads out and executes a program corresponding to the scan control function 441 from the memory 41. Step S13 is a step corresponding to the image generation function 442. Step S13 is a step in which the image generation function 442 is realized by the processing circuit 44 reading out and executing a program corresponding to the image generation function 442 from the memory 41. Step S14 corresponds to the display control function 443. Step S14 is a step in which the display control function 443 is realized by the processing circuit 44 reading out and executing a program corresponding to the display control function 443 from the memory 41.

  As described above, according to the first embodiment, the focal position can be changed at high speed without changing the quality of the X-ray to perform CT imaging with z-FFS. Image quality degradation can be prevented and image quality can be stabilized and improved. In addition, since the focal position on the anode changes, the focal position is not fixed at one location of the anode, and damage such as thermal melting of the anode is reduced.

Second Embodiment
In the first embodiment described above, z-FFS has been described, but in the second embodiment, FFS (hereinafter abbreviated as x-FFS) in which the focal position is changed in the X-axis direction (channel direction) is assumed. explain. In x-FFS, the sampling pitch in the X-axis direction can be equivalently reduced, and spatial resolution can be improved. The left and right direction of the X-ray tube 11 shown in FIG. 2 described above coincides with the body axis direction (Z-axis direction), and the focal position changes in the front-rear direction (X-axis direction) with respect to the sheet of FIG. A change in focus position in x-FFS is performed.

  FIG. 10 is a view showing a configuration example of the thermoelectronic adjustment mechanism 114, 115 according to the second embodiment, and shows only the thermoelectronic adjustment mechanism 114, 115 in a perspective view. The configuration of the X-ray tube 11 other than the thermoelectronic adjustment mechanisms 114 and 115 is the same as that shown in FIG. In FIG. 10, instead of the adjustment poles 114a and 114b facing each other at a distance in the Y-axis direction in FIG. 3, the first thermoelectron adjustment mechanism 114 faces an adjustment pole 114c facing a distance at the X-axis direction. , 114d are provided. Further, in the second thermal electron adjustment mechanism 115, adjustment poles 115c and 115d facing each other at a distance in the X-axis direction instead of the adjustment poles 115a and 115b facing each other at a distance in the Y-axis direction in FIG. Is provided. The adjustment poles 114c, 114d, 115c, and 115d can use an electric field for adjusting the trajectory, as in the case of the adjustment poles 114a, 114b, 115a, and 115b in FIG. Thereby, the direction in which the orbit of the thermal electron changes is perpendicular to the direction in which the orbit of the thermal electron changes in the case of FIG. 3 in the plane perpendicular to the traveling direction of the thermal electron in FIG. That is, when an electric field is used to adjust the orbit, the orbit of the thermal electron changes in the XZ plane.

  The configuration of the X-ray CT apparatus 1 is the same as that shown in FIG. The configuration of the X-ray high voltage device 17 is the same as that shown in FIG. The control method of the adjustment amount of the thermoelectronic adjustment mechanism 114, 115 is the same as that shown in FIGS. 5A and 5B.

  11A to 11C are diagrams showing an example of adjustment of the orbits of thermions by the thermionic adjustment mechanisms 114 and 115, and adjustment with the adjustment poles 114c and 114d facing in the X-axis direction as shown in FIG. In the configuration in which the poles 115c and 115d are provided, the case where an electric field is used to adjust the trajectory is shown. In this case, the orbits of thermions are adjusted to change in the circumferential direction of the anode 116.

FIG. 11A shows a case where the adjustment is off in both the first thermal electron adjustment mechanism 114 and the second thermal electron adjustment mechanism 115, and the orbit of the thermal electrons emitted from the cathode 113 Is not adjusted, and the anode 116 is irradiated. That is, the thermions emitted from the cathode 113 are drawn to the anode 116 to which a positive high potential difference is applied to the cathode 113, and are irradiated straight to a certain focal position _POT . The irradiation angle in this case is assumed to be θ _0T . The thermal electrons are irradiated to the anode 116 to generate X-rays.

FIG. 11B shows a case where the adjustment is on (ON) in both of the first thermal electron adjustment mechanism 114 and the second thermal electron adjustment mechanism 115, and the thermal electron adjustment mechanism 114 in the first thermal electron adjustment mechanism 114 The upward (X-axis positive direction) adjustment in the X-axis direction is performed with respect to the electron orbit, and the second thermoelectron adjustment mechanism 115 points downward (X-axis negative direction) in the X-axis direction with respect to the thermal electron orbit Shows the case where the adjustment of. By adjusting amount is previously appropriately set, an irradiation angle unchanged theta _0T when the as well as the anode 116 in FIG. 11A, the P _1T focal position is changed upward. In this case, since the irradiation angle to the anode 116 does not change, the quality of X-rays generated from the anode 116 does not change. That is, the irradiation angle to the anode 116 changes the path through which X-rays generated from near the surface of the anode 116 pass through the inside of the anode 116, affecting the radiation quality (the longer the path, the longer the wavelength of the absorption Although the quality of the wire increases by hardening, the quality of the radiation becomes constant because the irradiation angle does not change.

FIG. 11C shows a case where the adjustment is on (ON) in both of the first thermal electron adjustment mechanism 114 and the second thermal electron adjustment mechanism 115, and the thermal electron adjustment mechanism 114 in the first thermal electron adjustment mechanism 114 The downward adjustment in the X-axis direction is performed on the electron orbit, and the upward adjustment in the X-axis direction is performed on the thermal electron orbit in the second thermal electron adjustment mechanism 115. By adjusting amount is previously appropriately set, an irradiation angle unchanged theta _0T to the case as well as the anode 116 of FIG. 6A and 6B, the P _2T focal position is changed downward. Also in this case, since the irradiation angle to the anode 116 does not change, the quality of X-rays generated from the anode 116 does not change.

  The processing procedure of CT imaging by the X-ray CT apparatus 1 is the same as the flowchart shown in FIG. 8, but in the processing of image generation (step S13), in reconstruction in x-FFS, along with the rotation angle of the rotation frame 16 The difference of the position in the X-axis direction (channel direction) between the first focal position and the second focal position is taken into consideration to combine the projection data. That is, when the focal position is switched in the X-axis direction, the X-ray path from the X-ray tube 11 through the subject P to the X-ray detector 15 is increased. It is possible to improve the imaging resolution. In addition to switching to two focus positions, it is also possible to switch to three or more focus positions.

  As described above, according to the second embodiment, since the focal position can be changed at high speed without changing the quality of X-rays to perform CT imaging by x-FFS, unintended changes in the quality of the radiation Image quality degradation can be prevented and image quality can be stabilized and improved.

Third Embodiment
In the first embodiment, as shown in FIG. 3, the first thermoelectron adjustment mechanism 114 having adjustment poles 114a and 114b spaced in the Y axis direction, and adjustment poles 115a and 115b similarly spaced in the Y axis direction. The case where the X-ray tube 11 is provided with the second thermal electron adjustment mechanism 115 having the same has been described. In the second embodiment, as shown in FIG. 10, a first thermoelectron adjustment mechanism 114 having adjustment poles 114c and 114d spaced in the X axis direction, and adjustment poles 115c and 115d similarly spaced in the X axis direction. The case where the X-ray tube 11 is provided with the second thermal electron adjustment mechanism 115 having the same has been described. Then, the X-ray tube 11 can be provided with the respective configurations together, and only the directions can be switched and used, or both directions can be used simultaneously. For example, it can be applied to the z-FFS described in the first embodiment by the use of adjustment poles spaced apart in the X-axis direction and x described in the second embodiment by the use of adjustment poles spaced apart in the Y-axis direction Applicable to FFS. In addition, the simultaneous use of the adjustment pole separated in the X-axis direction and the adjustment pole separated in the Y-axis direction can be applied to an operation in which z-FFS and x-FFS are mixed. Thus, such an embodiment will be described as a third embodiment.

  FIG. 12 is a view showing a configuration example of the thermoelectronic adjustment mechanism 114, 115 according to the third embodiment, and shows only the thermoelectronic adjustment mechanism 114, 115 in a perspective view. In FIG. 12, in addition to the adjustment poles 114a and 114b facing each other at a distance in the Y axis direction, the first thermoelectron adjustment mechanism 114 includes adjustment poles 114c and 114d facing each other at a distance in the X axis direction. It is provided. In addition to the adjustment poles 115a and 115b facing each other at a distance in the Y axis direction, the second thermoelectron adjustment mechanism 115 is provided with adjustment poles 115c and 115d facing each other at a distance in the X axis direction. ing. The adjustment electrodes 114c, 114d, 115c, and 115d can use an electric field to adjust the trajectory.

  In FIG. 12, if the adjustment poles 114a and 114b of the first thermoelectron adjustment mechanism 114 and the adjustment poles 115a and 115b of the second thermoelectron adjustment mechanism 115 are used, as in the case of FIG. Can be used to adjust the Y-axis direction of the trajectory of Also, if the adjustment poles 114c and 114d of the first thermoelectron adjustment mechanism 114 and the adjustment poles 115c and 115d of the second thermoelectron adjustment mechanism 115 are used, the orbit of the thermoelectrons as in the case of FIG. Can be used for adjustment in the X-axis direction. Furthermore, using the adjustment electrodes 114a, 114b, 114c and 114d of the first thermoelectron adjustment mechanism 114 and the adjustment electrodes 115a, 115b, 115c and 115d of the second thermoelectron adjustment mechanism 115, three-dimensional XYZ The orbits of thermionic electrons can be adjusted in space.

  The table in FIG. 5A and the equation in FIG. 5B may be provided for each direction (Y-axis direction, X-axis direction) in which adjustment is performed, and it is assumed that both directions are considered as focus position indicators. The adjustment amount in both directions may be included in the second adjustment amount.

Fourth Embodiment
In the embodiments so far, the case where the X-ray tube 11 is provided with the two sets (two stages) of the thermal electron adjustment mechanisms 114 and 115 has been described, but the thermal electron adjustment mechanisms may be three or more stages.

  FIG. 13 is a view showing another configuration example of the X-ray tube 11, in addition to the first thermoelectron adjustment mechanism 114 and the second thermoelectron adjustment mechanism 115 in the rotary anode X-ray tube 11, A third thermal electronic adjustment mechanism 119 is provided. The third thermal electronic adjustment mechanism 119 includes the opposing adjustment pole 119a and the adjustment pole 119b. Further, as shown in FIG. 10, the adjustment poles 119a and 119b of the thermionic adjustment mechanism 119 may be replaced by the arrangement in the perpendicular direction (X-axis direction), or as shown in FIG. In addition, the arrangement in the perpendicular direction (X-axis direction) may be added. Other configurations of the X-ray tube 11 are similar to those shown in FIG. A third adjustment amount (including a direction) is added to the table of FIG. 5A and the equation of FIG. 5B for the third thermoelectron adjustment mechanism 119.

  The third thermoelectron adjustment mechanism 119 may be used for adjusting the orbit of the thermoelectrons similarly to the first and second thermoelectron adjustment mechanisms 114 and 115, or the beam of the thermoelectrons may be irradiated to the anode 116. It may be used to adjust the focal size of the part. However, an electric field is used to adjust the focal spot size. In the case of an electric field, the force acting on the thermoelectrons can be controlled by the relative potential with the cathode 113 with each of the pair of adjustment poles, but in the case of a magnetic field, the force acts on the thermoelectrons by the pair of adjustment poles It is. The focal point size of the irradiated part corresponds to the region on the anode 116 where the X-rays are generated, and affects the resolution of the image to be taken, so it should be managed to an appropriate value. It is possible to adjust to an appropriate value by the electronic adjustment mechanism 119. That is, the third thermoelectron adjustment mechanism 119 is based on an electric field, and the same negative voltage is applied to the adjustment electrodes 119a and 119b with respect to the cathode 113 to narrow the beam of the thermoelectrons and reduce the focal spot size. can do. In addition, the fourth, fifth,... Thermal electron adjustment mechanisms, that is, four or more thermal electron adjustment mechanisms are provided to adjust the trajectory of the thermal electrons or adjust the focal spot size of the thermal electrons. It is also good. The thermoelectron adjustment mechanism 119 is an example of a third thermoelectron adjustment unit.

Fifth Embodiment
FIG. 14 is a diagram showing another configuration example of the X-ray tube 11, and shows an example of a fixed anode. In FIG. 14, the X-ray tube 11 includes a housing 111, a cathode 113, a first thermoelectron adjustment mechanism 114, a second thermoelectron adjustment mechanism 115, and an anode 118. Compared to the configuration of FIG. 2, the rotary anode 116 is replaced by the stationary anode 118, and the rotation shaft 117 is eliminated. The anode 118 is, for example, a block member in which the surface on which the thermal electrons collide is made of tungsten, and a predetermined inclination angle is provided with respect to the trajectory of the thermal electrons emitted from the cathode 113. The first thermal electronic adjustment mechanism 114 and the second thermal electronic adjustment mechanism 115 may be replaced by the arrangement in the perpendicular direction (X-axis direction) as shown in FIG. As shown, an orthogonal (x-axis) orientation may be added. In the case of the fixed type anode, among the components of the X-ray high voltage device 17 shown in FIG. 4, the anode rotation drive power supply circuit 173 is not necessary.

  FIG. 15 is a diagram showing still another configuration example of the X-ray tube 11, and in addition to the first thermoelectron adjustment mechanism 114 and the second thermoelectron adjustment mechanism 115, the third thermoelectron adjustment mechanism 119 It is provided. The third thermal electronic adjustment mechanism 119 includes the opposing adjustment pole 119a and the adjustment pole 119b. Further, as shown in FIG. 10, the adjustment poles 119a and 119b of the thermionic adjustment mechanism 119 may be replaced by the arrangement in the perpendicular direction (X-axis direction), or as shown in FIG. In addition, the arrangement in the perpendicular direction (X-axis direction) may be added. Other configurations of the X-ray tube 11 are similar to those shown in FIG. As in the case of the rotary anode, the application of the third thermoelectron adjustment mechanism 119 may be used to adjust the orbit of the thermionic electron beam, or the size of the focal point size of the irradiated part of the beam of thermionic electron to the anode 116 It may be used for adjustment.

Sixth Embodiment
In the embodiments so far, the electric field is used to adjust the trajectories in the first thermoelectron adjustment mechanism 114, the second thermoelectron adjustment mechanism 115, and the third thermoelectron adjustment mechanism 119. However, instead of the electric field, a magnetic field can be used to adjust the trajectory of the thermions emitted from the cathode 113.

  When a magnetic field is used to adjust the trajectory, the adjustment poles of the first thermoelectron adjustment mechanism 114, the second thermoelectron adjustment mechanism 115, and the third thermoelectron adjustment mechanism 119 are, for example, the magnetic poles of an electromagnet, and flying The orbit of the thermoelectrons changes by the force received from the magnetic field. When a magnetic field is used to adjust the orbit, the direction of the force acting on the thermoelectrons is in a plane perpendicular to the direction in which the thermoelectrons travel with respect to the direction acting on the thermoelectrons when the electric field is used to adjust the orbit. It is the direction of the right angle (the direction orthogonal). That is, when an electric field is used to adjust the orbit, the orbit of the thermal electron changes in the YZ plane in FIG. 3 etc., and when a magnetic field is used to adjust the orbit, the XZ plane is orthogonal to the YZ plane. The orbit of the thermoelectrons changes.

  When the magnetic field is used, the first adjustment amount, the second adjustment amount, and the third adjustment amount with respect to the first thermal electronic adjustment mechanism 114, the second thermal electronic adjustment mechanism 115, and the third thermal electronic adjustment mechanism 119 are, for example, And the current value (including the polarity corresponding to the direction to be adjusted) supplied to the electromagnet coil of the adjustment pole. Thereby, when the focus position index is determined, the corresponding first adjustment amount, second adjustment amount and third adjustment amount can be obtained.

  According to at least one embodiment described above, the focal position can be changed without changing the quality of the irradiated X-ray.

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

DESCRIPTION OF SYMBOLS 1 X-ray CT apparatus 11 X-ray tube 113 Cathode 116, 118 Anode 114, 115, 119 Thermoelectronic adjustment mechanism 114a-114d, 115a-115d, 119a, 119b Adjustment pole 15 X-ray detector 17 X-ray high voltage apparatus 174 thermal Electronic adjustment mechanism drive circuit 21 data acquisition circuit 40 console unit 44 processing circuit

Claims (10)

A cathode generating thermal electrons;
An anode that receives thermal electrons emitted from the cathode and generates X-rays;
A first thermoelectron adjustment unit that adjusts the orbit of the thermoelectrons;
A second thermionic adjustment unit for further adjusting the trajectory of the thermoelectrons adjusted by the first thermionic adjustment unit;
By controlling the first thermoelectron adjustment unit and the second thermoelectron adjustment unit, the focal position of the thermoelectrons at the anode is maintained while the irradiation angle of the thermoelectrons to the anode is kept constant. Control unit to control
, An X-ray CT apparatus. The control unit is configured to change the focal position of the thermoelectrons along the circular radial direction of the anode having a circular outer periphery, and the second thermoelectron adjustment unit. And control
The X-ray CT apparatus according to claim 1. The control unit is configured to change the focal position of the thermions along the circular circumferential direction of the anode having a circular outer periphery, and the second thermionic adjustment Control the department,
The X-ray CT apparatus according to claim 1. And a third thermoelectron adjustment unit that adjusts the orbit of the thermoelectrons or the focal point size of the thermoelectrons on the anode,
The X-ray CT apparatus according to any one of claims 1 to 3. The control unit controls the focal position of the thermionic electron at the anode at a required position.
The X-ray CT apparatus according to any one of claims 1 to 4. The control unit performs switching control of the focal position of the thermoelectrons at the anode at a plurality of positions.
The X-ray CT apparatus according to any one of claims 1 to 4. The control unit performs switching control on a plurality of focal positions of the thermal electrons along the circular radial direction of the anode having a circular outer periphery,
The X-ray CT apparatus according to claim 6. The control unit performs switching control on a plurality of focal positions of the thermoelectrons along the circular circumferential direction of the anode having a circular outer periphery,
The X-ray CT apparatus according to claim 6. The control unit is configured to perform one of a plurality of focal positions of the thermions along the radial direction of the circle of the anode having a circular outer periphery and / or a plurality of focal positions of the thermoelectrons along the circumferential direction. , Switch control,
The X-ray CT apparatus according to claim 6. A cathode generating thermal electrons;
An anode that receives thermal electrons emitted from the cathode and generates X-rays;
A first thermoelectron adjustment unit that adjusts the orbit of the thermoelectrons;
A second thermionic adjustment unit for further adjusting the trajectory of the thermoelectrons adjusted by the first thermionic adjustment unit;
By controlling the first thermoelectron adjustment unit and the second thermoelectron adjustment unit, the focal position of the thermoelectrons at the anode is maintained while the irradiation angle of the thermoelectrons to the anode is kept constant. Control unit to control
X-ray generation system comprising

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