JP2012104392A - X-ray tube device and x-ray ct device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray tube device capable of improving cooling efficiency of the X-ray tube device having a plurality of X-ray generation points in a rotary shaft direction, and capable of preventing overheat in an X-ray tube, and to provide an X-ray CT device with the X-ray tube device mounted.SOLUTION: The X-ray tube device includes: a cathode for generating an electron beam; an anode for radiating an X-ray from X-ray generation points which are points irradiated with the electron beam; and an outer package for retaining the cathode and the anode in a vacuum atmosphere. The X-ray tube device has two pairs each including the cathode and the anode. The two anodes are disposed in such a manner that the rear sides of the surfaces having the X-ray generation points face each other. The X-ray tube device further includes a coolant channel to make a cooling medium flow between the two anodes.

Description

  The present invention relates to an X-ray tube apparatus and an X-ray CT (Computed Tomography) apparatus.

  An X-ray CT device is an X-ray tube device that irradiates a subject with X-rays, and an X-ray detector that detects X-ray dose transmitted through the subject as projection data by rotating the subject around the subject. The tomographic image of the subject is reconstructed using the acquired projection data from a plurality of angles, and the reconstructed tomographic image is displayed. The image displayed by the X-ray CT apparatus describes the shape of an organ in the subject and is used for diagnostic imaging.

  In recent developments of X-ray CT apparatuses, in order to expand the projection data acquisition range per rotation in the direction of the rotation axis, multiple rows of X-ray detectors in the direction of the rotation axis have been attempted. Although the projection data acquisition range is expanded as the number of X-ray detectors increases, projection data that is tilted with respect to the plane of the tomographic image is acquired as it approaches the X-ray detector array at the end in the rotation axis direction. It becomes. The projection data used for the reconstruction of the tomographic image is preferably acquired on the same plane as the tomographic image, and the projection data tilted with respect to the plane of the tomographic image causes so-called cone beam artifacts, resulting in image quality. Causes deterioration.

  Therefore, in Patent Document 1, in order to minimize the inclination of the acquired projection data, a plurality of X-ray generation points are arranged in the rotation axis direction in an X-ray CT apparatus in which X-ray detectors are arranged in multiple rows. Is disclosed. In particular, FIG. 2 of Patent Document 1 discloses an X-ray tube device in which two anodes having an X-ray generation point on the surface are arranged so that the back side of the surface having the X-ray generation point faces each other. .

Japanese Patent Laid-Open No. 2001-346791

  By the way, in the X-ray tube apparatus disclosed in FIG. 2 of Patent Document 1, the temperature between the two anodes tends to become high due to heat generated from the X-ray generation point. Overheating in the X-ray tube device has various adverse effects on the X-ray tube device, such as misalignment of the X-ray generation point due to thermal expansion of the rotating shaft of the anode and overheating of the solid lubricant used in the rotating shaft bearing of the anode. The resulting rotation failure.

  However, Patent Document 1 does not consider the cooling of the X-ray tube apparatus.

  Accordingly, an object of the present invention is to provide an X-ray tube apparatus having a structure capable of improving the cooling efficiency of an X-ray tube apparatus in which a plurality of X-ray generation points are arranged in the rotation axis direction and preventing overheating in the X-ray tube. And an X-ray CT apparatus equipped with the X-ray tube apparatus.

  In order to achieve the above object, the present invention is an X-ray tube device in which two anodes having X-ray generation points on the surface are arranged so that the back side of the surface having the X-ray generation points faces each other. A coolant channel for flowing a cooling medium is provided between the two anodes.

  Specifically, a cathode that generates an electron beam, an anode that emits X-rays from an X-ray generation point that is the point irradiated with the electron beam, and an envelope that holds the cathode and the anode in a vacuum atmosphere An X-ray tube device comprising two pairs of the cathode and the anode, the two anodes being arranged so that the back side of the surface having the X-ray generation point faces each other The X-ray tube apparatus further includes a refrigerant flow path for flowing a cooling medium between the two anodes.

  Further, the X-ray tube device, a multi-row X-ray detector that is disposed opposite to the X-ray tube device and detects X-rays transmitted through the subject, the X-ray tube device and the X-ray detector are provided. A rotating disk that is mounted and rotates around the subject, an image reconstruction device that reconstructs a tomographic image of the subject based on transmitted X-ray doses from a plurality of angles detected by the X-ray detector, and the image An X-ray CT apparatus comprising an image display device for displaying a tomographic image reconstructed by a reconstruction device, wherein the X-ray tube device has two X-ray generation points in the rotational axis direction of the rotating disk. An X-ray CT apparatus characterized by being arranged side by side.

  According to the present invention, it is possible to improve the cooling efficiency of an X-ray tube device in which a plurality of X-ray generation points are arranged in the rotation axis direction, and to provide an X-ray tube device having a structure capable of preventing overheating in the X-ray tube, And an X-ray CT apparatus equipped with the X-ray tube apparatus can be provided.

The block diagram which shows the whole structure of the X-ray CT apparatus of this invention Block diagram showing the overall configuration of the X-ray tube device of the first embodiment Sectional drawing which shows the structure of the refrigerant | coolant flow path of 1st embodiment. The block diagram which shows the whole structure of the X-ray tube apparatus of 2nd embodiment. The block diagram which shows the whole structure of the X-ray tube apparatus of 3rd embodiment.

  Hereinafter, preferred embodiments of an X-ray CT apparatus according to the present invention will be described with reference to the accompanying drawings. In the following description and the accompanying drawings, the same reference numerals are given to the constituent elements having the same functional configuration, and redundant description will be omitted.

  The overall configuration of the X-ray CT apparatus 1 to which the present invention is applied will be described with reference to FIG. The X-ray CT apparatus 1 includes a scan gantry unit 100 and a console 120.

  The scan gantry unit 100 includes an X-ray tube device 101, a rotating disk 102, a collimator 103, an X-ray detector 106, a data collection device 107, a bed 105, a gantry control device 108, and a bed control device 109. An X-ray control device 110. The X-ray tube device 101 is a device that irradiates a subject placed on a bed 105 with X-rays. The detailed configuration of the X-ray tube apparatus will be described later with reference to FIG. The collimator 103 is a device that limits the radiation range of X-rays emitted from the X-ray tube device 101.

  The rotating disk 102 includes an opening 104 into which the subject placed on the bed 105 enters, and is equipped with an X-ray tube device 101 and an X-ray detector 106, and rotates around the subject. The X-ray detector 106 is a device that measures the spatial distribution of transmitted X-rays by detecting X-rays that are disposed opposite to the X-ray tube device 101 and transmitted through the subject. These are two-dimensionally arranged in the direction of rotation of the rotating disk 102 and the direction of the rotation axis. The data collection device 107 is a device that collects the X-ray dose detected by the X-ray detector 106 as digital data. The gantry control device 108 is a device that controls the rotation of the rotary disk 102. The bed control device 109 is a device that controls the vertical and horizontal movements of the bed 105. The X-ray control device 110 is a device that controls electric power input to the X-ray tube device 101.

  The console 120 includes an input device 121, an image arithmetic device 122, a display device 125, a storage device 123, and a system control device 124. The input device 121 is a device for inputting a subject's name, examination date and time, imaging conditions, and the like, specifically a keyboard or a pointing device. The image computation device 122 is a device that performs CT processing on the measurement data sent from the data collection device 107 and performs CT image reconstruction. The display device 125 is a device that displays the CT image created by the image calculation device 122, and is specifically a CRT (Cathode-Ray Tube), a liquid crystal display, or the like. The storage device 123 is a device that stores data collected by the data collection device 107 and image data of a CT image created by the image calculation device 122, and is specifically an HDD (Hard Disk Drive) or the like. The system control device 124 is a device that controls these devices, the gantry control device 108, the bed control device 109, and the X-ray control device 110.

  The X-ray tube device 101 is controlled by the X-ray controller 110 controlling the power input to the X-ray tube device 101 based on the imaging conditions input from the input device 121, in particular, the X-ray tube voltage and the X-ray tube current. Irradiates the subject with X-rays according to imaging conditions. The X-ray detector 106 detects X-rays irradiated from the X-ray tube apparatus 101 and transmitted through the subject with a large number of X-ray detection elements, and measures the distribution of transmitted X-rays. The rotating disk 102 is controlled by the gantry control device 108, and rotates based on the photographing conditions input from the input device 121, particularly the rotation speed. The couch 105 is controlled by the couch controller 109 and operates based on the photographing conditions input from the input device 121, particularly the helical pitch.

  By repeating the X-ray irradiation from the X-ray tube device 101 and the measurement of the transmitted X-ray distribution by the X-ray detector 106 along with the rotation of the rotating disk 102, projection data from various angles is acquired. The acquired projection data from various angles is transmitted to the image calculation device 122. The image calculation device 122 reconstructs the CT image by performing back projection processing on the transmitted projection data from various angles. The CT image obtained by the reconstruction is displayed on the display device 125.

(First embodiment)
The configuration of the X-ray tube apparatus 101 according to the first embodiment will be described with reference to FIG. FIG. 2 is drawn so that the rotation axis of the rotating disk 102 is in the left-right direction. The X-ray tube device 101 includes X-ray tubes 2a and 2b that generate X-rays, and a container 3 that stores the X-ray tubes 2a and 2b.

  Since the X-ray tube 2a and the X-ray tube 2b have the same structure, the structure of the X-ray tube 2a will be described below, and the description of the X-ray tube 2b will be omitted. The X-ray tube 2a includes a cathode 8a that generates an electron beam, an anode 6a to which a positive potential is applied to the cathode 8a, and an envelope 4a that holds the cathode 8a and the anode 6a in a vacuum atmosphere.

  The cathode 8a includes a filament or a cold cathode and a focusing electrode. The filament is formed by winding a high melting point material such as tungsten in a coil shape, and is heated when a current is passed to emit thermoelectrons. A cold cathode is formed by sharpening a metal material such as nickel or molybdenum, and emits electrons by field emission when an electric field is concentrated on the cathode surface. The focusing electrode forms a focusing electric field for focusing the emitted electrons toward the X-ray generation point on the anode 6a. The filament or cold cathode and the focusing electrode are at the same potential.

  The anode 6a includes a target and an anode base material. The target is made of a material having a high melting point and a large atomic number, such as tungsten. When electrons emitted from the cathode 8a collide with the X-ray generation point on the target, X-rays 11a are emitted from the X-ray generation point. The anode base material holds the target and is made of a material having high thermal conductivity such as copper. The target and the anode base material are at the same potential.

  The envelope 4a holds the cathode 8a and the anode 6a in a vacuum atmosphere in order to electrically insulate between the cathode 8a and the anode 6a. The envelope 4a is provided with a radiation window for radiating the X-ray 11a to the outside of the X-ray tube 2a. The radiation window 218 is made of a material having a small atomic number such as beryllium having a high X-ray transmittance. The potential of the envelope 4a is the ground potential.

  Electrons emitted from the cathode 8a are accelerated by a voltage of about 100 kV applied between the cathode and the anode to become an electron beam. When the electron beam is focused by the focusing electric field and collides with the X-ray generation point on the target, X-rays 11a are generated from the X-ray generation point. The energy of the generated X-ray is determined by a high voltage applied between the cathode and the anode, so-called tube voltage. The dose of X-rays generated depends on the amount of electrons emitted from the cathode, the so-called tube current and the tube voltage.

  Only about 1% of the energy of the electron beam is converted to X-rays, and most of the remaining energy is heat. In the X-ray tube apparatus 101 used in the X-ray CT apparatus 1, the tube voltage is hundreds of tens kV and the tube current is several hundreds mA, so the anode 6a is heated with a heat quantity of several tens kW. In order to prevent the anode 6a from being overheated and melted by such heating, the anode 6a is rotated by a magnetic field generated by the stator coil 5a. By rotating the anode 6a, the X-ray generation point where the electron beam collides always moves, so the temperature of the X-ray generation point can be kept lower than the melting point of the target, and the anode 6a is overheated and melted Can be prevented.

  As described above, the X-ray tube 2a described above and the X-ray tube 2b having the same structure as the X-ray tube 2a are arranged so that the back sides of the surfaces having the X-ray generation points of the anodes 6a and 6b face each other. And stored in the container 3. The container 3 in which the X-ray tubes 2a and 2b are stored is filled with an insulating oil 10 that electrically insulates the X-ray tubes 2a and 2b and serves as a cooling medium.

  As described above, since the anode 6a and the anode 6b are heated with a heat quantity of several tens of kW, the temperature between the anode 6a and the anode 6b tends to be high. Therefore, in the present embodiment, the refrigerant flow path 7 for flowing the cooling medium is provided between the X-ray tube 2a and the X-ray tube 2b, and the space between the anode 6a and the anode 6b is efficiently cooled. A cooling medium cooled by a cooler provided outside the container 3 of the X-ray tube device 101, for example, cooling water or cooling oil, is introduced into the refrigerant flow path 7 through the inlet 3a and the pipe 9a. The cooling medium flowing into the refrigerant flow path 7 absorbs heat between the X-ray tube 2a and the X-ray tube 2b and then returns to the cooler through the pipe 9b and the outlet 3b. In FIG. 2, the X-ray 11a and the pipe 9a are drawn so as to overlap each other, but the pipe 9a is preferably arranged so as not to overlap the radiation path of the X-ray 11a.

  Since the path composed of the inlet 3a, the pipe 9a, the refrigerant flow path 7, the pipe 9b, and the outlet 3b is separated from the container 3, the insulating oil that fills the container 3 and the refrigerant flow path The cooling medium flowing through 7 can be of different types. For example, the container 3 can be filled with insulating oil suitable for electrical insulation, and a cooling medium suitable for cooling can flow in the refrigerant flow path 7.

  The structure of the refrigerant flow path 7 will be described with reference to FIG. 3 is a cross-sectional view taken along the line AA in FIG. The refrigerant flow path 7 has an inlet 7a into which the cooling medium flows and an outlet 7b from which the cooling medium flows out. The interior of the refrigerant flow path 7 is partitioned by a wall formed of a plurality of concentric rings around the rotation axes of the anodes 6a and 6b, and further on a straight line from the inlet 7a to the outlet 7b. A circulation port is provided. The size of the circulation port is reduced from the inlet 7a toward the center of the refrigerant flow path 7. By adopting such a shape, a part of the cooling medium flowing in from the inlet 7a is directed to the center of the refrigerant flow path 7, and the cooling medium not directed to the center of the refrigerant flow path 7 is circulated along the ring. As a result, the entire space between the anode 6a and the anode 6b can be cooled.

  The material of the refrigerant flow path 7 is preferably a material having high thermal conductivity, and is appropriately selected according to the envelopes 4a and 4b. For example, if the envelopes 4a and 4b are made of glass, the refrigerant flow path 7 is made of aluminum nitride, and if the envelopes 4a and 4b are made of metal, the refrigerant flow path 7 is made of copper or aluminum.

  Further, since the X-ray generation point of the anodes 6a and 6b becomes the highest temperature, it is preferable to arrange the inlet 7a in the vicinity of the X-ray generation point. Specifically, the inlet 7a is arranged so that the cooling medium flows in a direction of a straight line connecting the rotation centers of the anodes 2a and 2b and the X-ray generation point.

  Furthermore, by rotating the anode 6a and the anode 6b in the opposite directions, the temperature distribution between the anode 6a and the anode 6b can be made symmetrical with respect to the straight line connecting the inlet 7a and the outlet 7b. Can be prevented. Note that the rotation in the opposite direction of the anode 6a and the anode 6b means that the X-ray generation point on the anode 6b is a figure when the X-ray generation point on the anode 6a is rotated in the direction toward the back of FIG. It is to rotate in the direction toward the front of the paper.

(Second embodiment)
The configuration of the X-ray tube apparatus 101 according to the second embodiment will be described with reference to FIG. The difference from the first embodiment is the path of the cooling medium that has flowed out of the refrigerant flow path. Each configuration will be described below. In addition, about the same structure as 1st embodiment, it is set as the same code | symbol and description is abbreviate | omitted.

  In the present embodiment, the cooling medium flowing out from the refrigerant flow path 7 is discharged into the container 3, circulates through the container 3, and then returns to the cooler through the outlet 3b. That is, in this embodiment, the insulating oil 10 filled in the container 3 and the cooling medium flowing in the refrigerant flow path 7 can be made common. Further, since the insulating oil 10 in the container 3 is also circulated and cooled by the cooler, the cooling efficiency in the container 3 can be improved.

(Third embodiment)
The configuration of the X-ray tube apparatus 101 according to the third embodiment will be described with reference to FIG. The difference from the first embodiment is the structure of the X-ray tube. Each configuration will be described below. In addition, about the same structure as 1st embodiment, it is set as the same code | symbol and description is abbreviate | omitted.

  In the present embodiment, a pair of the cathode 8a and the anode 6a and a pair of the cathode 8b and the anode 6b are held in one envelope 4. That is, the X-ray tube apparatus 101 of this embodiment includes one X-ray tube 2 having two X-ray generation points. The refrigerant flow path 7 may constitute a part of the envelope 4 or may be disposed outside the envelope 4. In FIG. 5, the refrigerant flow path 7 and the pipe 9b are drawn so as not to be connected, but the pipe 9b is connected to the refrigerant flow path 7 so as to avoid the envelope 4.

  When the refrigerant flow path 7 constitutes a part of the envelope 4, or when the envelope 4 is a transparent material, for example, glass, and the refrigerant flow path 7 is disposed outside the envelope 4, It is preferable that the surface of the coolant channel 7 facing the anodes 6a and 6b is blackened. By blackening the surfaces facing the anodes 6a and 6b, the refrigerant flow path 7 can efficiently absorb the radiant heat from the anodes 6a and 6b, and the cooling rate can be improved.

  In addition, this invention is not limited to the form demonstrated by embodiment. For example, an X-ray CT apparatus having an even number of X-ray generation points may be provided by arranging a plurality of the X-ray tube apparatuses of the first embodiment to the third embodiment in the rotation axis direction of the rotating disk.

  Moreover, you may implement combining the some component disclosed by embodiment suitably. For example, as described in the second embodiment, a cooling medium may be circulated in the X-ray tube of the third embodiment.

  1 X-ray CT device, 100 scan gantry unit, 101 X-ray tube device, 102 rotating disk, 103 collimator, 104 opening, 105 bed, 106 X-ray detector, 107 data collection device, 108 gantry control device, 109 bed control Device, 110 X-ray control device, 120 console, 121 input device, 122 image processing device, 123 storage device, 124 system control device, 125 display device, 2, 2a, 2b X-ray tube, 3, container, 4, 4a , 4b Envelope, 5a, 5b Stator coil, 6a, 6b Anode, 7 Refrigerant flow path, 7a Inlet, 7b Outlet, 8a, 8b Cathode, 9a, 9b Piping, 10 Insulating oil, 11a, 11b X-ray

Claims (6)

A cathode that generates an electron beam; an anode that emits X-rays from an X-ray generation point that is the point irradiated with the electron beam; and an envelope that holds the cathode and the anode in a vacuum atmosphere. X-ray tube device,
Two pairs of the cathode and the anode are provided, and the two anodes are arranged so that the back side of the surface having the X-ray generation point faces each other.
An X-ray tube apparatus further comprising a refrigerant flow path for flowing a cooling medium between two anodes. The X-ray tube apparatus according to claim 1,
The anode is disc-shaped,
The inside of the refrigerant flow path is partitioned by a wall formed of a plurality of concentric rings centering on the center of the anode disk, and the cooling medium flows from the inlet into which the cooling medium flows. An X-ray tube device characterized in that a circulation port is provided on a straight line toward an outflow port that flows out. The X-ray tube apparatus according to claim 2,
The X-ray tube apparatus according to claim 1, wherein the size of the circulation port decreases from the inflow port toward the center of the refrigerant flow path. The X-ray tube apparatus according to claim 2,
The X-ray tube apparatus according to claim 1, wherein the refrigerant flow path is provided with the inlet near the X-ray generation point. The X-ray tube apparatus according to claim 2,
The X-ray tube apparatus according to claim 1, wherein the anode is a rotating anode, and the two anodes are rotated in opposite directions. The X-ray tube apparatus according to any one of claims 1 to 5, a multi-row X-ray detector arranged to face the X-ray tube apparatus and detecting X-rays transmitted through a subject, and the X-ray detector A tomographic image of the subject is reproduced based on a rotating disk mounted with the X-ray tube device and the X-ray detector and rotating around the subject, and transmitted X-ray doses from a plurality of angles detected by the X-ray detector. An X-ray CT apparatus comprising: an image reconstructing device that configures; and an image display device that displays a tomographic image reconstructed by the image reconstructing device,
2. The X-ray CT apparatus according to claim 1, wherein the X-ray tube apparatus is arranged such that two X-ray generation points are arranged in a direction of a rotation axis of the rotating disk.

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