JP2020010973A - X-ray CT apparatus and X-ray tube apparatus - Google Patents

Abstract

To provide an X-ray of output higher than ever before with a small focal size.SOLUTION: An X-ray CT apparatus according to an embodiment includes an X-ray tube, an X-ray detector, a first rotation part, and a second rotation part. The X-ray tube includes a cathode for irradiating a thermal electron, and an annular anode for generating an X-ray upon receipt of the thermal electron, which is provided over the periphery of an imaging center. The X-ray detector is provided at a position which is irradiated with the X-ray generated by the anode of the X-ray tube. The first rotation part holds the cathode, the anode, and the X-ray detector rotatably in a circumferential direction. The second rotation part is held by the first rotation part and holds the anode rotatably in a circumferential direction.SELECTED DRAWING: Figure 3

Description

  An embodiment of the present invention relates to an X-ray CT (Computed Tomography) apparatus and an X-ray tube apparatus.

  There is a medical image diagnostic apparatus that generates medical image data in which a body tissue of a subject is imaged. Examples of the medical image diagnostic apparatus include an X-ray CT apparatus and an MRI (Magnetic Resonance Imaging) apparatus. The X-ray CT apparatus generates an axial section or three-dimensional CT image data of the subject based on an electric signal based on the X-ray detected by the X-ray detector by irradiating the subject with X-rays.

  An X-ray CT apparatus includes an X-ray tube that generates X-rays. The X-ray tube is a vacuum tube that generates X-rays by irradiating thermoelectrons from a cathode (filament) to an anode (target) by applying a high voltage. In order to obtain high output with a small focal point in an X-ray tube, there is a problem that the focal plane of the target becomes hot.

JP-A-58-11538

  The problem to be solved by the present invention is to obtain an X-ray having a smaller focal spot size and a higher output than before.

  The X-ray CT apparatus according to the embodiment includes an X-ray tube, an X-ray detector, a first rotating unit, and a second rotating unit. The X-ray tube includes a cathode that emits thermoelectrons, and an annular anode that receives the thermoelectrons to generate X-rays and is provided around the center of the imaging center. The X-ray detector is provided at a position where the X-ray generated by the anode of the X-ray tube is irradiated. The first rotating unit holds the cathode, the anode, and the X-ray detector so as to be rotatable in the circumferential direction. The second rotating unit is held by the first rotating unit, and holds the anode rotatably in the circumferential direction.

FIG. 1 is a schematic diagram illustrating a configuration of an X-ray CT apparatus according to an embodiment. FIG. 2 is a schematic view of a configuration of a ring target according to a comparative example as viewed from the front. FIG. 3 is a schematic view of a first configuration example of a target according to the X-ray CT apparatus according to the embodiment, as viewed from the front. FIG. 4 is a side view showing a first configuration example of the target shown in FIG. 3 and a configuration of peripheral members thereof in the X-ray CT apparatus according to the embodiment. FIG. 5 is a schematic view of the operation of the target shown in FIG. 3 as viewed from the front in the X-ray CT apparatus according to the embodiment. FIG. 6 is a schematic view of a second configuration example of the target according to the X-ray CT apparatus according to the embodiment, as viewed from the front. FIG. 7 is a side view showing a second configuration example of the target shown in FIG. 6 and a configuration of peripheral members thereof in the X-ray CT apparatus according to the embodiment.

  Hereinafter, embodiments of an X-ray CT apparatus and an X-ray tube apparatus will be described in detail with reference to the drawings.

  The data collection method using the X-ray CT apparatus includes a rotation / rotation (RR) method in which an X-ray tube and an X-ray detector rotate as one body around the subject, and a ring-shaped method. There are various systems such as a fixed / rotation (SR) system in which a large number of detection elements are arrayed and only an X-ray tube rotates around the subject. The present invention can be applied to any method. Hereinafter, the X-ray CT apparatus according to the embodiment will be described taking as an example a case where a third-generation rotation / rotation method, which is currently dominant, is adopted.

  FIG. 1 is a schematic diagram illustrating a configuration of an X-ray CT apparatus according to the embodiment.

  FIG. 1 shows an X-ray CT apparatus 1 according to the embodiment. The X-ray CT apparatus 1 includes a gantry device 10, a bed device 30, and a console device 40. The gantry device 10 and the bed device 30 are installed in an examination room. The gantry device 10 collects X-ray detection data (also referred to as “pure raw data”) on a subject (for example, a patient) P placed on the bed device 30. In FIG. 1, for convenience of description, a plurality of gantry devices 10 are drawn on the left and right, but as a practical configuration, there is one gantry device 10.

  The console device 40 is installed in a control room adjacent to the examination room. The console device 40 generates raw data by performing preprocessing on detection data for a plurality of views, and reconstructs and displays a CT image by performing reconstruction processing on the raw data.

  The gantry device 10 includes an X-ray tube (synonymous with “X-ray tube device”) 11, an X-ray detector 12, a first rotating unit (for example, a first rotating frame) 13, an X-ray high-voltage device 14, The apparatus includes a device 15, a wedge 16, a collimator 17, a data acquisition circuit (DAS: Data Acquisition System) 18, and a fixed part (fixed frame) 19. The gantry device 10 is an example of a gantry.

  The X-ray tube 11 is provided on the first rotating frame 13. The X-ray tube 11 is a vacuum tube including a cathode (cathode) 11a and an annular anode (anode) 11b (gray portion in FIG. 1). The anode 11b has a structure in which a target is attached to the surface of a copper lump. Hereinafter, the anode and the target will be described with the same reference numerals 11b. The target 11b generates X-rays by irradiating thermoelectrons from the cathode 11a to the target 11b by applying a high voltage from the X-ray high voltage device 14. The detailed configuration of the X-ray tube 11 will be described later with reference to FIGS.

  In the embodiment, a single-tube X-ray CT apparatus and a so-called multi-tube X-ray CT apparatus in which a plurality of pairs of an X-ray tube and an X-ray detector are mounted on a rotating ring are also used. Applicable. Note that the X-ray tube 11 is an example of an X-ray irradiation unit.

  The X-ray detector 12 is provided on the first rotating frame 13 so as to face the X-ray tube 11. Specifically, the X-ray detector 12 is provided at a position where the X-ray generated by the cathode of the X-ray tube 11 is irradiated. The X-ray detector 12 detects X-rays emitted from the X-ray tube 11 and outputs detection data corresponding to the X-ray dose to the DAS 18 as an electric signal. The X-ray detector 12 has, for example, a plurality of X-ray detection element rows in which a plurality of X-ray detection elements are arranged in a channel direction along one arc around the focal point of the X-ray tube. The X-ray detector 12 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 a channel direction are arranged in a slice direction (row direction, row direction).

  Further, the X-ray detector 12 is, for example, an indirect conversion type detector having a grid, a scintillator array, and an optical sensor array. The scintillator array has a plurality of scintillators, and the scintillator has a scintillator crystal that outputs light having a photon amount corresponding to an incident X-ray dose. The grid has an X-ray shielding plate disposed on the surface of the scintillator array on the X-ray incident side and having a function of absorbing scattered X-rays. The grid may be called a collimator (one-dimensional collimator or two-dimensional collimator). The optical sensor array has a function of converting an electric signal according to the amount of light from the scintillator, and includes, for example, an optical sensor such as a photomultiplier tube (photomultiplier: PMT).

  Note that the X-ray detector 12 may be a direct conversion type detector having a semiconductor element that converts incident X-rays into an electric signal. The X-ray detector 12 is an example of an X-ray detector.

  The first rotating frame 13 supports the X-ray tube 11 and the X-ray detector 12 in opposition. The first rotating frame 13 is an annular frame that rotates the X-ray tube 11 and the X-ray detector 12 integrally under the control of the control device 15 described below. The first rotating frame 13 may be provided with an X-ray high-voltage device 14 or a DAS 18 in addition to the X-ray tube 11 and the X-ray detector 12, and may be supported. In addition, the first rotating frame 13 is an example of a first rotating unit.

  As described above, the X-ray CT apparatus 1 rotates the first rotating frame 13 that supports the X-ray tube 11 and the X-ray detector 12 so as to face each other around the patient P, thereby providing a plurality of views, that is, a plurality of views. The 360-degree detection data of the patient P is collected. Note that the CT image reconstruction method is not limited to the full scan reconstruction method using 360 ° detection data. For example, the X-ray CT apparatus 1 may adopt a half reconstruction method of reconstructing a CT image based on detection data for a half circumference (180 °) + a fan angle.

  The X-ray high-voltage device 14 is provided on the first rotating frame 13 or the fixed frame 19 that is a non-rotating part that holds the first rotating frame 13 rotatably. The X-ray high-voltage device 14 has an electric circuit such as a transformer (transformer) and a rectifier. The X-ray high-voltage device 14 includes a high-voltage generator (not shown) having a function of generating a high voltage applied to the X-ray tube 11 under the control of a control device 15 described below, and a control by the control device 15 described below. Below, an X-ray control device (not shown) for controlling the output voltage according to the X-ray emitted by the X-ray tube 11 is provided. The high voltage generator may be of a transformer type or an inverter type. In FIG. 1, for convenience of explanation, the X-ray high-voltage device 14 is disposed at a position in the positive direction of the x-axis with respect to the X-ray tube 11. It may be arranged at a position in the direction.

  The control device 15 includes a processing circuit and a memory, and a driving mechanism such as a motor and an actuator. The configuration of the processing circuit and the memory is the same as that of the processing circuit 44 and the memory 41 of the console device 40 described later, and thus the description is omitted.

  The control device 15 has a function of receiving an input signal from an input interface (not shown), which will be described later, attached to the console device 40 or the gantry device 10, and controls the operation of the gantry device 10 and the couch device 30. For example, the control device 15 performs control to rotate the first rotating frame 13 in response to an input signal, control to tilt the gantry device 10, and control to operate the bed device 30 and the top board 33. Note that the control for tilting the gantry device 10 is performed by the control device 15 based on the tilt angle (tilt angle) information input by the input interface attached to the gantry device 10 based on the first axis centered on an axis parallel to the X-axis direction. This is realized by rotating the rotating frame 13. The control device 15 may be provided on the gantry device 10 or on the console device 40. The control device 15 is an example of a control unit.

  Further, the control device 15 controls the rotation angle of the X-ray tube 11 and the wedge 16 and the collimator 17 described below based on imaging conditions input from an input interface described later attached to the console device 40 and the gantry device 10. Control behavior.

  The wedge 16 is provided on the first rotating frame 13 so as to be arranged on the X-ray emission side of the X-ray tube 11. The wedge 16 is a filter for adjusting the X-ray dose emitted from the X-ray tube 11 under the control of the control device 15. Specifically, the wedge 16 is a filter that transmits and attenuates the X-rays emitted from the X-ray tube 11 so that the X-rays emitted to the patient P from the X-ray tube 11 have a predetermined distribution. It is. For example, the wedge 16 (wedge filter, bow-tie filter) is a filter formed by processing aluminum so as to have a predetermined target angle and a predetermined thickness.

  The collimator 17 is also called an X-ray aperture or a slit, and is provided on the first rotating frame 13 so as to be arranged on the X-ray emission side of the X-ray tube 11. The collimator 17 is a lead plate or the like for narrowing the irradiation range of the X-ray transmitted through the wedge 16 under the control of the control device 15, and forms an X-ray irradiation opening by a combination of a plurality of lead plates and the like.

  The DAS 18 is provided on the first rotating frame 13. The DAS 18 performs an amplification process on an electric signal output from each X-ray detection element of the X-ray detector 12 under the control of the control device 15, and converts the electric signal into a digital signal under the control of the control device 15. An A / D (Analog to Digital) converter that converts the signal into a signal, and generates detection data after amplification and digital conversion. The detection data for a plurality of views generated by the DAS 18 is transferred to the console device 40.

  Here, the detection data generated by the DAS 18 includes a photodiode provided on the fixed frame 19 of the gantry 10 by optical communication from a transmitter having a light emitting diode (LED) provided on the first rotating frame 13. The data is transmitted to the receiver and transferred to the console device 40. The transmission method of the detection data from the first rotating frame 13 to the fixed frame 19 of the gantry device 10 is not limited to the above-described optical communication, and any method may be adopted as long as it is a non-contact type data transmission. Absent. The first rotating frame 13 is an example of a rotating unit.

  The fixed frame 19 forms a bore W for arranging the patient P inside in the radial direction. The fixed frame 19 rotatably supports the first rotating frame 13.

  The couch device 30 includes a base 31, a couch driving device 32, a top plate 33, and a support frame. The couch device 30 is a device that places a patient P to be scanned and moves the patient P under the control of the control device 15.

  The base 31 is a housing that supports the support frame 34 so as to be movable in a vertical direction (y-axis direction). The couch driving device 32 is a motor or an actuator that moves the table 33 on which the patient P is placed in the long axis direction (z-axis direction) of the table 33. The top plate 33 provided on the upper surface of the support frame 34 is a plate having a shape on which the patient P can be placed.

  The bed driving device 32 may move the support frame 34 in the long axis direction (z-axis direction) of the top plate 33 in addition to the top plate 33. Further, the bed driving device 32 may be moved together with the base 31 of the bed device 30. When the present invention is applied to the standing CT, a method of moving a patient moving mechanism corresponding to the top plate 33 may be used. Further, in the case of performing an imaging involving a relative change of the positional relationship between the imaging system of the gantry device 10 and the top plate 33, such as a scano imaging for helical scan or positioning, the relative change of the relative position is not performed. It may be performed by driving the top plate 33, by running the fixed frame 19 of the gantry device 10, or by a combination thereof.

  In the embodiment, the longitudinal direction of the rotation axis of the first rotation frame 13 or the top plate 33 of the bed device 30 in the non-tilt state is orthogonal to the z-axis direction and the z-axis direction, and is horizontal to the floor surface. The axis direction is orthogonal to the x-axis direction and the z-axis direction, and the axis direction perpendicular to the floor is defined as the y-axis direction.

  The console device 40 includes a memory 41, a display 42, an input interface 43, and a processing circuit 44. Although the console device 40 is described as being separate from the gantry device 10, the gantry device 10 may include the console device 40 or some of the components of the console device 40. In the following description, it is assumed that the console device 40 executes all functions with a single console, but these functions may be executed by a plurality of consoles. The console device 40 is an example of a medical image processing device.

  The memory 41 includes, for example, a semiconductor memory device such as a random access memory (RAM) and a flash memory, a hard disk, an optical disk, and the like. The memory 41 may be configured by a portable medium such as a USB (Universal Serial Bus) memory and a DVD (Digital Video Disk). The memory 41 stores various processing programs (including an OS (Operating System) as well as application programs) used in the processing circuit 44 and data necessary for executing the programs. In addition, the OS may include a GUI (Graphic User Interface) that makes extensive use of graphics for displaying information on the display 42 for the operator and allows basic operations to be performed by the input interface 43.

  The memory 41 stores, for example, detection data before preprocessing, raw data after preprocessing and before reconstruction, and CT images after reconstruction. The pre-processing means at least one of logarithmic conversion processing, offset correction processing, sensitivity correction processing between channels, beam hardening processing, and the like for the detection data. Further, a cloud server connectable to the X-ray CT apparatus 1 via a communication network such as the Internet receives a storage request from the X-ray CT apparatus 1 and stores detection data, raw data, and CT images. May be done. Note that the memory 41 is an example of a storage unit.

  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 user, and the like. For example, the display 42 is a liquid crystal display, a CRT (Cathode Ray Tube) display, an OLED (Organic Light Emitting Diode) display, or the like. The display 42 may be provided on the gantry device 10. Further, the display 42 may be a desktop type, or may be configured by a tablet terminal or the like that can wirelessly communicate with the console device 40 main body. The display 42 is an example of a display unit.

  The input interface 43 includes an input device that can be operated by an operator such as a technician, and an input circuit that inputs a signal from the input device. Input devices include a mouse, a keyboard, a trackball, switches, buttons, a joystick, a touchpad for performing input operations by touching an operation surface, a touch screen in which a display screen and a touchpad are integrated, and a non-display device using an optical sensor. This is realized by a contact input circuit, a voice input circuit, and the like. When the input device receives an input operation from the operator, the input circuit generates an electric signal corresponding to the input operation and outputs the electric signal to the processing circuit 44. The input interface 43 may be provided on the gantry device 10. Further, the input interface 43 may be configured by a tablet terminal or the like that can wirelessly communicate with the console device 40 main body. The input interface 43 is an example of an input unit.

  The processing circuit 44 controls the entire operation of the X-ray CT apparatus 1. The processing circuit 44 means a dedicated or general-purpose CPU (Central Processing Unit), MPU (Micro Processor Unit), or GPU (Graphics Processing Unit), as well as an ASIC, a programmable logic device, and the like. Examples of the programmable logic device include a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA). No.

  Further, the processing circuit 44 may be configured by a single circuit, or may be configured by a combination of a plurality of independent processing circuit elements. In the latter case, the memory may be provided separately for each processing circuit element, or a single memory may store programs corresponding to the functions of a plurality of processing circuit elements.

  The processing circuit 44 implements a system control function 441, a preprocessing function 442, and a reconfiguration processing function 443 by executing a program stored in the memory 41. Note that all or a part of the functions 441 to 443 is not limited to a case where the functions are realized by executing a program of the console device 40, and may be a case where the console device 40 is provided as a circuit such as an ASIC. . Further, all or a part of the functions 441 to 443 may be provided not only in the console device 40 but also in the control device 15.

  The system control function 441 controls the operations of the X-ray tube 11, the X-ray detector 12, the first rotating frame 13, and the like via the control device 15 in accordance with a preset scan condition to execute a CT scan. And a function of collecting detection data for a plurality of views from the control device 15. For example, the scan conditions include a tube current mA, a tube voltage kV, an X-ray intensity control condition (modulation condition), a rotation speed of the X-ray tube 11 (or the first rotating frame 13), and the like regarding the irradiated X-ray. Note that the system control function 441 is an example of a system control unit.

  The preprocessing function 442 includes a function of performing preprocessing on detection data for a plurality of views collected by the system control function 441 to generate raw data for a plurality of views. The preprocessing function 442 is an example of a preprocessing unit.

  The reconstruction processing function 443 includes a function of generating CT image data by image reconstruction processing based on raw data for a plurality of views after preprocessing by the preprocessing function 442. The reconstruction processing function 443 has a function of storing CT image data in the memory 41, a function of displaying CT image data as a CT image on the display 42, and a function of outputting CT image data via a network interface (not shown). It may include a function to transmit to the device. The reconfiguration processing function 443 is an example of a reconfiguration processing unit.

  Subsequently, the configuration of the target of the X-ray tube according to the comparative example will be described with reference to FIG. The configuration and operation of the target 11b of the X-ray tube 11 according to the embodiment will be described with reference to FIGS.

  FIG. 2 is a schematic view of the configuration of a ring target 11b 'according to a comparative example, as viewed from the front.

  FIG. 2 shows a first rotating frame 13 and an X-ray tube 11 ′ fixed to the first rotating frame 13. The X-ray tube 11 'includes a cathode 11a' and a ring target 11b '. In FIG. 2, the rotation center axis of the first rotating frame 13 is defined as "C", and the rotation center axis of the ring target 11b 'is defined as "D'".

  The cathode 11 a ′, the ring target 11 b ′, and the X-ray detector 12 rotate around the rotation center axis C together with the first rotating frame 13. The ring target 11b 'rotates further around the rotation center axis D' with respect to the first rotating frame 13. That is, by rotating the ring target 11b 'around the rotation center axis D', the X-ray tube 11 'focuses on a surface (hereinafter, referred to as a "focal plane") U' of the ring target 11b 'on the cathode 11a side. X-rays are generated while shifting the position F '.

  X-rays generated by the ring target 11b 'penetrate the patient disposed in the bore W and are detected by the X-ray detector 12 held on the first rotating frame 13. As described above, on the first rotating frame 13 rotated around the rotation center axis C, the ring target 11b 'further rotated around the rotation center axis D' moves at each focal position F 'on the focal plane U'. By generating the line, a CT scan for acquiring data of a plurality of views is performed.

  When an attempt is made to obtain a high output with a small focal point in the X-ray tube 11 ′, the focal plane U ′ of the ring target 11 b ′ becomes hot because the area of the focal plane U ′ of the ring target 11 b ′ is small. Further, it is conceivable to adopt a method of expanding the area of the focal plane U 'of the ring target 11b' in order to overcome the high temperature with a structure in which the position of the rotation center axis D 'of the ring target 11b' is maintained. However, it is difficult to adopt this method due to the installation space of the ring target 11b 'and the effect of the centrifugal force of the rotation of the first rotating frame.

  Therefore, it is considered to increase the area of the focal plane U 'of the target 11b' while shifting the position of the rotation center axis D 'of the ring target 11b' to near the rotation center axis C. On the other hand, the axial cross section of the CT image is preferably parallel to the xy plane, and the size of the X-ray detector 12 is not changed in order to use the third-generation X-ray detector 12. Is preferred. Therefore, assuming that the axial cross section of the CT image is parallel to the xy plane and that the size of the X-ray detector 12 is not changed, the position of the rotation center axis D ′ is shifted to near the rotation center axis C. Consider expanding the area of the focal plane U 'of the target 11b'.

  If the axial section of the CT image is parallel to the xy plane and the size of the X-ray detector 12 is not changed, and the position of the rotation center axis D ′ is shifted to near the rotation center axis C, the target By adopting a configuration in which the rotation center axis D ′ of 11b ′ has a predetermined inclination angle from the rotation center axis C, the area of the focal plane U ′ can be increased. Alternatively, by adopting a configuration in which the diameter of the target 11b 'is larger than the rotation diameter of the X-ray detector 12, the area of the focal plane U' can be increased. That is, the target 11 b ′ is provided so that the rotation trajectory is outside the rotation trajectory of the X-ray detector 12. In the former case, there is no need to provide the target 11b outside the rotation trajectory of the X-ray detector 12, which is advantageous in terms of miniaturization of the gantry device 10. Hereinafter, the first configuration example will be described with reference to FIGS. 3 to 5, and the second configuration example will be described with reference to FIGS. 6 and 7.

(First Configuration Example of Target 11b)
FIG. 3 is a schematic view of the first configuration example of the target 11b as viewed from the front. FIG. 4 is a side view illustrating a first configuration example of the target 11b illustrated in FIG. 3 and a configuration of peripheral members thereof.

  The first configuration example of the target 11b shown in FIGS. 3 and 4 includes a first rotating frame 13 and a target 11b (gray portions in FIGS. 3 and 4) which are arranged so that the rotation center axes are different from each other. Prepare. In FIG. 4, the rotation center axis of the first rotating frame 13 is defined as “C”, and the rotation center axis of the target 11 b with respect to the first rotating frame 13 is defined as “D”. 3 and 4, the intersection of the rotation center axis C and the rotation center axis D is defined as the imaging center, that is, the rotation center I.

  The target 11b will be described with reference to FIG. The target 11b is provided in an annular shape so as to extend around the rotation center axis D including the rotation center I.

  The cathode 11a, the target 11b, and the X-ray detector 12 rotate around the rotation center axis C including the rotation center I together with the first rotation frame 13. The target 11b further rotates around the rotation center axis D including the imaging center I with respect to the first rotation frame 13. In other words, by rotating the target 11b further with respect to the first rotating frame 13, the X-ray tube 11 generates X-rays while shifting the focal position F on the focal plane U of the target 11b.

  The X-rays generated at the target 11 b and having passed through the wedge 16 and the collimator 17 (shown in FIG. 1) penetrate the patient disposed in the bore W and are held by the X-ray detector 12 held by the first rotating frame 13. Is detected by In this manner, on the first rotating frame 13 rotated around the rotation center axis C, the target 11b further rotated around the rotation center axis D generates X-rays at each focal position F on the focal plane U. Then, a CT scan for collecting data of a plurality of views is performed.

  Compared with the ring target 11b 'shown in FIG. 2, in the first configuration example of the target 11b shown in FIG. 3, since the area of the focal plane U' can be expanded to the focal plane U, high output can be achieved with a small focal point. There is an effect that it can be obtained. Further, in the target 11b, the temperature of the focal plane U can be suppressed from increasing. Further, in the target 11b, there is an effect that the centrifugal resistance of the target 11b due to rotation of the rotating frame 13 is improved.

  The target 11b and its peripheral members shown in FIG. 3 will be described with reference to FIG. 4 shows the configuration of the X-ray tube 11 and the like when the cathode 11a of the X-ray tube 11 is located on the upper side. On the other hand, the right side of FIG. 4 shows the configuration of the X-ray tube 11 and the like when the cathode 11a of the X-ray tube 11 is located on the lower side. That is, the right side of FIG. 4 shows the configuration of the X-ray tube 11 and the like when the rotation angle of the first rotating frame 13 is different from the left side by 180 degrees.

  The first rotating frame 13 holds the vacuum vessel V and the X-ray detector 12. When the first rotation frame 13 rotates around the rotation center axis C, the vacuum vessel V and the X-ray detector 12 rotate around the rotation center axis C integrally with the first rotation frame 13.

  Further, the vacuum vessel V includes a support section B, a second rotating section (for example, a second rotating frame) R, and an X-ray tube 11 therein. The support B is fixed to the inner wall of the vacuum vessel V, and rotates together with the vacuum vessel V. The second rotating frame R is held by the support portion B via a plurality of ball bearings L arranged in the circumferential direction of the support portion B so as to be rotatable in the circumferential direction with respect to the support portion B. The target 11b of the X-ray tube 11 is fixed to the second rotating frame R and rotates together with the second rotating frame R. In addition, the support portion B, the second rotating frame R, and the target 11b of the X-ray tube 11 are arranged along a circumference around the rotation center axis D. On the other hand, the cathode 11a of the X-ray tube 11 is fixed to the inner wall of the vacuum vessel V and rotates together with the vacuum vessel V.

  The first rotating frame 13 supports driving means for driving the second rotating frame R to rotate. As the driving means, for example, a direct drive type motor (not shown) provided along the ring of the target 11b, that is, a DD motor is used. The target 11b fixed to the second rotating frame R by the operation of the DD motor rotating the second rotating frame R around the rotation center axis D with respect to the support portion B via the plurality of ball bearings L Rotates around the rotation center axis D. That is, the vacuum vessel V and the X-ray detector 12 can rotate together with the first rotating frame 13, and the target 11 b inside the vacuum vessel V moves together with the second rotating frame R inside the rotating vacuum vessel V. Further rotatable.

  Here, the target 11b is arranged such that the rotation center axis D overlaps the rotation center axis C at the rotation center I. The target 11b is arranged so that a straight line connecting the focal position F and the center position of the detection surface of the X-ray detector 12 is vertical (parallel to the y-axis). Further, the target angle of the target 11b is formed such that X-rays are emitted about a linear direction connecting the focal position F and the center position of the detection surface of the X-ray detector 12. Thereby, the axial cross section of the obtained CT image becomes parallel to the xy plane. The rotation center axis D of the second rotation frame R has a predetermined inclination angle α in the yz plane with respect to the rotation center axis C of the first rotation frame 13. The inclination angle α is appropriately determined according to the number of rows of detection elements of the X-ray detector 12 (the number in the direction parallel to the z-axis). Thus, there is no need to change the size of the X-ray detector 12.

  In addition, compared with the comparative example shown in FIG. 2, in FIG. 4, since the target 11b etc. are arrange | positioned with the fixed inclination angle (alpha), it seems that the gantry apparatus 10 becomes large in az-axis direction. However, in the X-ray tube 11, there is no need to configure a mechanism (rotor and stator, etc.) for rotating the conventional target 11b '(shown in FIG. 2) according to the comparative example in the Z-axis direction. Since the installation of a large-sized cooling device becomes unnecessary by increasing the product, the enlargement of the gantry device 10 can be suppressed to a minimum.

  Next, the rotation speed and rotation direction of the first rotating frame 13 and the target 11b will be described with reference to FIG. FIG. 5 is a schematic view of the operation of the target 11b shown in FIG. 3 as viewed from the front. The target 11b is configured to rotate at a speed exceeding “0” with respect to the first rotating frame 13. That is, the target 11b is configured to rotate at a speed exceeding “0” with respect to the first rotating frame 13 in the same direction as the rotating direction of the first rotating frame 13, or It is configured to rotate at a speed exceeding “0” with respect to the first rotating frame 13 in a direction opposite to the rotating direction of the rotating frame 13.

  As shown in FIG. 5, the rotation of the first rotating frame 13 causes the cathode 11a to rotate clockwise at the speed V1. On the other hand, the target 11b rotates clockwise at a relative speed V2 with respect to the first rotating frame 13 due to the rotation of the second rotating frame R. The relative speed V2 is not “0”. When the relative speed V2 is “0”, the rotation of the first rotating frame 13 causes the cathode 11a and the target 11b to rotate at the same speed in the same direction, and the irradiation position of the thermoelectrons on the target 11b is dispersed. This is because they do not.

  The rotation direction of the first rotating frame 13 and the like (the rotating direction at the speed V1) and the rotating direction of the target 11b and the like with respect to the first rotating frame 13 (the rotating direction at the speed V2) are the same. It is not limited to the case. The same effect can be obtained even if the direction of rotation of the first rotating frame 13 and the like and the direction of rotation of the target 11b and the like with respect to the first rotating frame 13 are opposite.

  Although the case of the target 11 b rotating with respect to the first rotating frame 13 has been described with reference to FIGS. 3 to 5, a configuration in which an annular target fixed to the fixed frame 19 is adopted may be adopted. Conceivable. However, in that case, it is necessary to provide an X-ray detector having channels for the entire circumference or half. According to the target 11b shown in FIGS. 3 to 5 which rotates with respect to the first rotating frame 13, an X-ray detector provided in a third-generation X-ray CT apparatus, a data processing method, and an X-ray high-voltage apparatus , High voltage cables can be diverted.

  As described above, according to the first configuration example of the target 11b illustrated in FIGS. 3 to 5, it is possible to obtain an X-ray having a smaller focal spot size and a higher output than before, while suppressing an increase in the size of the gantry device 10. it can. Further, according to the first configuration example of the target 11b, it is possible to suppress the increase in the temperature of the focal plane U, so that there is no need to install a cooling device, and the centrifugal resistance of the target 11b due to the rotation of the rotating frame 13 is reduced. This has the effect of significantly improving.

(Second Configuration Example of Target 11b)
In the second configuration example shown in FIGS. 6 and 7, similarly to the first configuration example shown in FIGS. 3 and 4, the axial section of the CT image is parallel to the xy plane and the X-ray detector 12 is assumed not to be changed. On the other hand, the second configuration example shown in FIG. 6 and FIG. 7 is different from the first configuration example shown in FIG. 3 and FIG. The target 11b (the gray portion in FIGS. 6 and 7) is arranged outside.

  FIG. 6 is a schematic view of the second configuration example of the target 11b as viewed from the front. FIG. 7 is a side view illustrating a second configuration example of the target 11b illustrated in FIG. 6 and a configuration of peripheral members thereof.

  The target 11b will be described with reference to FIG. The target 11b is provided in an annular shape so as to extend around the rotation center axis C including the rotation center I. The target 11b is arranged so that its rotation orbit is outside the rotation orbit of the X-ray detector 12. The position and size of the X-ray detector 12 are the same as those shown in FIG.

  The cathode 11a, the target 11b, and the X-ray detector 12 rotate around the rotation center axis C together with the first rotating frame 13. The target 11b further rotates around the rotation center axis C with respect to the first rotating frame 13. In other words, by rotating the target 11b further with respect to the first rotating frame 13, the X-ray tube 11 generates X-rays while shifting the focal position F on the focal plane U of the target 11b.

  The X-rays generated at the target 11 b and having passed through the wedge 16 and the collimator 17 (shown in FIG. 1) penetrate the patient disposed in the bore W and are held by the X-ray detector 12 held by the first rotating frame 13. Is detected by In this way, on the first rotating frame 13 rotated around the rotation center axis C, the target 11b further rotating around the rotation center axis C generates X-rays at each focal position F on the focal plane U. , A CT scan is performed to collect data for multiple views.

  Compared to the ring target 11b 'shown in FIG. 2, in the second configuration example of the target 11b shown in FIG. 6, since the area of the focal plane U' can be expanded to the focal plane U, the description will be made with reference to FIG. There is an effect similar to the effect obtained.

  The target 11b and its peripheral members shown in FIG. 6 will be described with reference to FIG. The left side of FIG. 7 shows the configuration of the X-ray tube 11 and the like when the cathode 11a of the X-ray tube 11 is located on the upper side, similarly to the left side of FIG. On the other hand, the right side of FIG. 7 shows the configuration of the X-ray tube 11 and the like when the cathode 11a of the X-ray tube 11 is located on the lower side, similarly to the right side of FIG. In FIG. 7, the description of the same parts as those in FIG. 4 is omitted.

  The support portion B, the second rotating frame R, and the target 11b of the X-ray tube 11 are arranged along a circumference around the rotation center axis C, and the rotation trajectory of the target 11b is detected by X-ray. It is arranged so that it may be outside the rotation track of container 12. On the other hand, the cathode 11a of the X-ray tube 11 is fixed to the inner wall of the vacuum vessel V and rotates together with the vacuum vessel V.

  Here, the target angle of the target 11b is formed such that X-rays are emitted with a center in a linear direction connecting the focal position F and the center position of the detection surface of the X-ray detector 12. Thereby, the axial cross section of the obtained CT image becomes parallel to the xy plane. The target 11b is arranged so that its rotation orbit is outside the rotation orbit of the X-ray detector 12. Thus, there is no need to change the size of the X-ray detector 12.

  The rotation speed and rotation direction of the target 11b and the second rotating frame R are the same as those described with reference to FIG.

  When the target 11b shown in FIGS. 6 and 7 is adopted, the arrangement and the size of the X-ray detector 12 are the same as those in the case where the target 11b shown in FIGS. The distance from the focal position F of the X-ray detector 12 has changed. That is, when the target 11b shown in FIGS. 6 and 7 is adopted, the X-rays incident on each X-ray detecting element of the X-ray detector 12 are compared with the case where the target 11b shown in FIGS. The angle of the line changes. Therefore, when the target 11b shown in FIGS. 6 and 7 is adopted, it is preferable that a grid different from the case where the target 11b shown in FIGS. 3 and 4 is adopted is arranged on the front surface of the X-ray detector 12. Each X-ray shielding plate constituting the grid is provided on the grid so as to have an inclination angle corresponding to the focal position.

  As described above, according to the second configuration example of the target 11b illustrated in FIGS. 6 and 7, the same effect as that of the first configuration example of the target 11b illustrated in FIGS.

  According to at least one embodiment described above, it is possible to obtain an X-ray with a smaller focal spot size and higher output than before.

  Although several embodiments of the present invention have been described, these embodiments are provided by way of example 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 changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1 X-ray CT apparatus 11 X-ray tube 11a Cathode 11b Target 12 X-ray detector 13 First rotating frame 19 Fixed frame V Vacuum container B Supporting part R Second rotating frame L Plural ball bearings

Claims (9)

An X-ray tube including: a cathode that irradiates thermoelectrons; an X-ray that receives the thermoelectrons to generate X-rays; and an annular anode that is provided around an imaging center.
An X-ray detector provided at a position where the X-ray generated by the anode of the X-ray tube is irradiated;
A first rotating unit that holds the cathode, the anode, and the X-ray detector so as to be rotatable in a circumferential direction;
A second rotating unit held by the first rotating unit and holding the anode rotatably in a circumferential direction;
An X-ray CT apparatus comprising: The rotation center axis of the second rotation unit has a predetermined inclination angle with respect to the rotation center axis of the first rotation unit.
The X-ray CT apparatus according to claim 1. The second rotating unit is configured to rotate in the same direction as the rotating direction of the first rotating unit, or in the opposite direction,
The X-ray CT apparatus according to claim 1. The second rotating unit is configured to rotate at a speed exceeding “0” with respect to the first rotating unit,
The X-ray CT apparatus according to claim 1. The anode is arranged such that the rotation trajectory of the anode due to the rotation of the second rotation unit is outside the rotation trajectory of the X-ray detector due to the rotation of the first rotation unit,
The X-ray CT apparatus according to claim 1. The anode has a target angle formed such that the X-rays are emitted with a center in a linear direction connecting a focal position and a center position of the detection surface of the X-ray detector,
The X-ray CT apparatus according to claim 1. The first rotating unit holds a vacuum container,
The vacuum vessel has therein a support section and the cathode fixed to the vacuum vessel, the second rotating section rotatably held by the support section with respect to the support section, And the anode fixed to the rotating part of
The X-ray CT apparatus according to claim 1. The second rotating portion is held by the support portion so as to be rotatable in the circumferential direction with respect to the support portion, via a plurality of ball bearings arranged in the circumferential direction of the support portion.
The X-ray CT apparatus according to claim 7. A cathode for irradiating thermoelectrons,
An annular anode provided around the imaging center to generate X-rays upon receiving the thermoelectrons,
A second rotating unit that is held by the first rotating unit that holds the cathode, the anode, and the X-ray detector rotatably in the circumferential direction, and that holds the anode rotatably in the circumferential direction;
An X-ray tube device comprising: