JP5468911B2 - X-ray tube apparatus and X-ray CT apparatus using the same - Google Patents

Description

  The present invention relates to an X-ray tube apparatus and an X-ray CT apparatus using the X-ray tube apparatus, and more particularly to recoil electron capture and a cooling technique against heat generated by recoil electron capture.

  In recent years, in the X-ray CT apparatus, there has been a demand for further shortening of the imaging time, and there is a demand for increasing the irradiation amount of the X-ray beam emitted from the X-ray tube apparatus. On the other hand, the X-ray tube device has an anode (rotary anode target) and a cathode, and electrons emitted from the cathode are accelerated to the rotating anode target side by a high voltage applied between the electrodes and collided with each other. It is the structure which generates a line.

  At this time, among the electrons colliding with the rotating anode target, there are those that repeat recoiled electrons as recoil electrons without being converted into heat or X-rays. The direction and intensity of recoil electrons vary depending on the applied voltage and the electric field near the focal point, but usually about 50% or more of the incident electrons recoil in all directions. The recoil electrons return to a portion other than the focal plane of the anode target or rush into the vacuum envelope, but heat and X-rays are also generated by the return or rush of the recoil electrons.

  In particular, X-rays generated by recoil electrons become a noise component with respect to X-rays generated from the focal plane of the rotating anode target, and prevent uniform X-rays from being obtained. Further, the heat generated by the recoil electrons becomes a factor that raises the temperature of the rotating anode target and the like.

  Therefore, in order to solve these problems, the recoiled electrons generated by capturing the recoiled electrons and returning to the rotating anode target or the recoiled electrons entering the vacuum envelope are reduced. Pipe devices have been proposed. This rotary anode X-ray tube apparatus includes a recoil electron capturing structure (collector) that functions as a trap for capturing recoil electrons between a rotary anode target and an electron emission source (cathode). However, there is a problem that some recoil electrons that cannot be captured by the collector also recoil in the direction of the rotation axis of the rotary anode target.

  As a technique for solving this problem, for example, there is a technique described in Patent Document 1. In the technique described in Patent Document 1, the rotating anode target and the recoil electron capturing structure are rotated together, and the recoil electrons are captured by the structure.

Japanese Patent No. 3910468

  However, in the technique described in Patent Document 1, since the structure for capturing recoil electrons is integrated with the rotary anode target, the load on the bearing becomes larger than before. For this reason, there is a concern that the life of the bearing will be shortened. In the X-ray tube apparatus described in Patent Document 1, it is necessary to design the bearing with a higher strength than that of the rotating anode alone, which increases costs. Furthermore, in the structure for capturing recoil electrons described in Patent Document 1, since the structure for capturing recoil electrons is directly connected in the vicinity of the bearing rotation shaft, heat due to the capture of recoil electrons is applied to the bearing. Since it flows, it is not preferable. In particular, since the temperature of the bearing increases the temperature of the lubricant, there is a concern that the lubricant may deteriorate quickly or the bearing may deteriorate early.

  The present invention has been made in view of these problems, and an object of the present invention is to suppress heating of a structural member due to capture of recoil electrons and to suppress heating of a rotary bearing of a rotary anode target. To provide technology.

  (1) In order to solve the above problems, a cathode that emits an electron beam, an anode target that collides the electron beam and generates X-rays having the collision position as a focal position, and a rotating mechanism that rotates the anode target And an envelope that holds the cathode and the anode target in a vacuum, the X-ray tube device being formed on the inner wall surface side of the envelope, the electron beam collision surface side of the anode target It is an X-ray tube apparatus provided with the 1st uneven | corrugated | grooved part which protrudes in this.

  (2) In order to solve the above problems, a cathode that emits an electron beam, an anode target that collides the electron beam and generates X-rays having the collision position as a focal position, and a rotating mechanism that rotates the anode target And an envelope for holding the cathode and the anode target in a vacuum, wherein the X-ray tube apparatus is an area on the electron beam collision surface side of the anode target, and at least the electron beam collision area It is an X-ray tube apparatus provided with the 2nd uneven | corrugated | grooved part which is formed in the area | region except and protrudes in the inner wall face side of the said envelope.

  (3) In order to solve the above-mentioned problem, a cathode that emits an electron beam, an anode target that collides the electron beam and generates X-rays having the collision position as a focal position, and a rotating mechanism that rotates the anode target And an envelope that holds the cathode and the anode target in a vacuum, the X-ray tube device being formed on the inner wall surface side of the envelope, the electron beam collision surface side of the anode target A first concavo-convex portion arranged in parallel at a predetermined interval from the rotation center of the anode target, and an area on the electron beam collision surface side of the anode target, and at least the electron beam collision area A second concavo-convex portion formed in a region excluding and arranged in parallel at a predetermined interval from the rotation center of the anode target at a predetermined interval, and the first concavo-convex portion and the second concavo-convex portion Irregularities and is X-ray tube device which is disposed in combination with each other.

  (4) In order to solve the above-mentioned problem, the subject is irradiated with X-rays. The X-ray tube device according to any one of (1) to (3), and the subject disposed opposite to the X-ray tube device. An X-ray detector for detecting transmitted X-rays, a scanner equipped with the X-ray tube device and the X-ray detector and rotating around the subject, and projection data detected by the X-ray detector A data collection unit that collects every two focal positions, an image reconstruction device that reconstructs a tomographic image of the subject based on projection data collected by the data collection unit, and a tomogram that is reconstructed by the image reconstruction device An X-ray CT apparatus including an image display device that displays an image.

  According to the present invention, heating of the structural member due to capture of recoil electrons can be suppressed, and heating of the rotary bearing of the rotary anode target can also be suppressed.

  Other effects of the present invention will become apparent from the description of the entire specification.

It is sectional drawing for demonstrating schematic structure of the X-ray tube apparatus of Embodiment 1 of this invention. It is a figure for demonstrating an example of the trajectory of the recoil electron in the X-ray tube apparatus of Embodiment 1 of this invention. It is sectional drawing for demonstrating schematic structure of the X-ray tube apparatus of Embodiment 2 of this invention. It is sectional drawing for demonstrating schematic structure of the X-ray tube apparatus of Embodiment 3 of this invention. It is sectional drawing for demonstrating schematic structure of the X-ray tube apparatus of Embodiment 4 of this invention. It is a figure for demonstrating an example of the electric potential distribution between the cathode and recoil-electron capture structure in the X-ray tube apparatus of Embodiment 4 of this invention, and a rotating anode target, and the trajectory of a recoil electron. It is sectional drawing for demonstrating schematic structure of the X-ray tube apparatus of Embodiment 5 of this invention. It is sectional drawing for demonstrating schematic structure of the other X-ray tube apparatus of Embodiment 1 of this invention. It is a figure for demonstrating schematic structure of the X-ray CT apparatus of Embodiment 6 of this invention.

  Embodiments to which the present invention is applied will be described below with reference to the drawings. However, in the following description, the same components are denoted by the same reference numerals, and repeated description is omitted.

<Embodiment 1>
<overall structure>
FIG. 1 is a cross-sectional view for explaining a schematic configuration of an X-ray tube apparatus according to Embodiment 1 of the present invention. Hereinafter, an overall configuration of the X-ray tube apparatus according to Embodiment 1 will be described with reference to FIG. In the following description, a case where the present invention is applied to a so-called anode grounded X-ray tube apparatus in which the rotating anode target 14 and the recoil electron capturing structure 12 are at ground potential will be described. However, the present invention is not limited thereto. It will never be done. For example, the present invention can also be applied to a so-called neutral point grounded X-ray tube apparatus in which the recoil electron capturing structure 12 is set to the ground potential, the rotary anode target 14 is set to the positive potential, and the cathode 11 is set to the negative potential.

  As shown in FIG. 1, in the X-ray tube apparatus 1 according to the first embodiment, the cathode 11, the rotary anode target 14, the rotary support mechanism 16 including a rotor (not shown), and the rotary anode target 14 and the rotary support mechanism 16 are connected. The rotary anode support structure 15 is enclosed in the vacuum envelope 2 for maintaining a high vacuum. The vacuum envelope 2 is housed inside the tube container 18 and is configured to be irradiated with an X-ray beam from a radiation window 13 formed on the peripheral side surface of the tube container 18. In addition, the X-ray tube apparatus 1 of the first embodiment has a double structure of the tube container 18 and the vacuum envelope 2, and the vacuum envelope 2 and the tube container 18 in which the inside is maintained in a vacuum. Between them, an insulating refrigerant is sealed so as to be circulated. In the first embodiment, the configuration other than the rotary anode target 14 and the vacuum envelope 2 is the same as the conventional configuration. Therefore, in the following description, the configuration of the rotary anode target 14 and the vacuum envelope 2 will be described. Will be described in detail.

  The cathode 11 is configured to be supported by a cathode support, and is configured to be fixed at a position where an electron beam (not shown) emitted from the cathode 11 is irradiated to the electron beam collision surface side of the rotating anode target 14. Yes. Further, in the X-ray tube device 1 of Embodiment 1, the X-ray tube device 1 is formed so as to cover the outer peripheral portion of the cathode 11 and the rotating anode target 14 side, and has an opening in a region corresponding to the irradiation path of the electron beam irradiated from the cathode 11. It is the structure provided with the recoil-electron capture structure (collector) 12 in which is formed.

  The rotating anode target 14 is connected to a rotor (not shown) via a rotating anode support structure 15 to constitute a rotating body. The rotating body is supported in a cantilever manner by the rotation support mechanism 16 so as to be rotatable. That is, in the X-ray tube apparatus 1 of the first embodiment, one end side of the rotary anode support structure 15 is connected to the center position of the rotary anode target 14, and the rotary support mechanism 16 including a rotor on the other end side. Is arranged. With such a configuration, the position on the electron beam collision surface side of the rotating anode target 14 irradiated with the electron beam emitted from the cathode 11 is sequentially moved. The detailed configuration of the rotating anode target 14 will be described later.

  A stator (stator coil) 17 that generates an induction electromagnetic field is disposed outside the vacuum envelope 2 at a position surrounding a rotation support mechanism 16 including a rotor (not shown). A voltage of about 500 V is applied to the stator 17 to generate an induction electromagnetic field, and the rotating anode target 14 connected to the rotor is rotated at high speed by the induction electromagnetic field generated by the stator 17. It has a configuration.

<Structure of fin structure>
Next, based on FIG. 1, the detailed structure and operation | movement of the X-ray tube apparatus of Embodiment 1 are demonstrated. In the X-ray tube apparatus 1 according to Embodiment 1 shown in FIG. 1, the cathode 11 has a filament (not shown), and a predetermined voltage is applied between the cathode 11 and the rotating anode target 14. Due to this potential difference, electrons (thermoelectrons) emitted from the cathode 11 are accelerated, collide with the focal plane of the rotating anode target 14 as an electron beam, and converted into X-rays.

  At this time, about 50% of the electrons emitted from the cathode 11 bounce back as recoil electrons, that is, backscatter. The bounced electrons (recoil electrons) are captured by the collector 12 due to the potential difference between the cathode 11 and the collector 12, but some of the recoil electrons are scattered in the axial center direction (rotation center axis) of the rotary anode target 14. . Furthermore, secondary and tertiary recoil electrons that are bounced back by other structures are scattered.

  Here, in the X-ray tube apparatus 1 of the first embodiment, an uneven portion (fin structure, second structure) is formed on the electron beam collision surface side of the rotary anode target 14, that is, on the side facing the cathode 11 of the rotary anode target 14. (Uneven portion) 21 is formed. In particular, in the X-ray tube apparatus 1 according to the first embodiment, a plurality of cylindrical fins having different diameters are formed on the electron beam collision surface side of the rotating anode target 14. It is formed by arranging a structure in which cylindrical fins are arranged on the electron beam collision surface side. Thus, the fin structure 21 of the first embodiment in which the respective cylindrical fins are arranged so as to align the rotation center axis of the rotary anode target 14 and the center position of each cylindrical fin is formed. Is possible. Further, the fin structure 21, which is an example of a concavo-convex structure that captures recoil electrons on the electron collision surface side of the rotating anode target 14, has a shape that can withstand centrifugal loads, and is deformed by heat and load to face the opposing surface With high fin efficiency in consideration of cooling.

  Further, in the X-ray tube apparatus according to the first embodiment, the unevenness protruding in the arrangement direction of the rotary anode target 14 on the inner wall surface facing the electron beam collision surface side of the rotary anode target 14 in the vacuum envelope 2. A portion (fin structure, first uneven portion) 22 is formed. At this time, the X-ray tube apparatus 1 according to the first embodiment uses a stainless steel (SUS) vacuum envelope 2 in order to maintain a high vacuum. Therefore, for example, by forming the fin structure 22 from the same stainless steel (SUS) as the vacuum envelope 2, the fin structure 22 has heat resistance and heat conductivity from the fin structure 22 to the wall surface of the vacuum envelope 2. However, the constituent material may be other materials.

  In the X-ray tube apparatus 1 of the first embodiment, for example, when a plurality of cylindrical stainless steel (SUS) fins having different diameters are formed on the inner wall surface of the vacuum envelope 2, the vacuum envelope is formed. Cylindrical fins formed in advance on the inner wall surface 2 are arranged by a joining method having heat resistance such as welding. At this time, the fin structure 22 of the first embodiment is formed by arranging the cylindrical fins in a row so that the rotation center axis of the rotary anode target 14 and the center position of each cylindrical fin are aligned. The

  However, the fin structure 22 of Embodiment 1 is not limited to the structure mentioned above. For example, it may be formed as described below. First, when a plurality of cylindrical fins having different diameters are formed on the inner wall surface of the vacuum envelope 2, the wall surface thickness of the inner wall surface is formed in advance with an inner wall surface thickness that takes into account the amount of protrusion of the fins. Next, a plurality of concentric grooves are formed on the inner wall surface. The fin structure 22 formed on the inner wall surface of the vacuum envelope 2 can also be obtained by setting the center position of the groove portion to a position corresponding to the rotation center axis of the rotary anode target 14.

  In the X-ray tube apparatus 1 of Embodiment 1, the unevenness of the fin structure 21 formed on the rotary anode target 14 and the fin structure 22 formed on the inner wall surface of the vacuum envelope 2 are combined with each other. It is the composition which becomes. That is, the positions of the regions (apparent groove portions (concave portions) of the fin structure 22) formed between adjacent fins forming the fin structure 22 and the fins (convex portions) of the fin structure 21 are The protrusions of the fin structure 21 are inserted into the recesses of the fin structure 22. Further, the positions of the regions (apparent groove portions (concave portions) of the fin structure 21) formed between adjacent fins forming the fin structure 21 and the fins (convex portions) of the fin structure 22 are also defined. The protrusions of the fin structure 22 are inserted into the recesses of the fin structure 21. With such a configuration, the vicinity of the rotation center axis of the rotary anode target 14 is shielded from recoil electrons by the fin structures 21 and 22, so that the recoil electrons are located near the rotation center axis. We can prevent going.

  On the other hand, as the rotary anode target 14 becomes hot, the heat radiation from the entire rotary anode target 14 is also increased. At this time, in the X-ray apparatus of the first embodiment, the fin structure 22 is disposed in the vicinity of the fin structure 21, and the surface area of the opposing surfaces of the fin structures 21 and 22 is also increased. The radiant heat radiated from the fin structure 21 is efficiently absorbed by the fin structure 22. As a result, since the cooling rate of the rotary anode target 14 is improved, it is possible to suppress the temperature rise of the rotary anode target 14, the rotary anode support structure 15 connected to the rotary anode target 14, and the rotary support mechanism 16. It becomes possible.

  In recent X-ray tube devices, a rotating anode accompanying continuous irradiation of a high-power electron beam at the same focal position in response to increasing the output of the generated X-ray beam and continuous output of the X-ray beam for a long time. In order to prevent the deterioration of the target 14, the rotational speed of the rotary anode target 14 is increasing, and the burden on the rotary support mechanism 16 is increasing. For this reason, not only the temperature of the rotating anode target 14 but also the temperature of the rotating support mechanism 16 is required to be lowered. On the other hand, in the X-ray tube apparatus of the first embodiment, in addition to the heat generated by the irradiation of the electron beam to the rotating anode target 14, the heat generated by the collision of the recoil electrons can be efficiently cooled. 14 can be suppressed. As a result, heat transmitted to the rotation support mechanism 16 can be reduced, and the reliability of the rotation support mechanism 16, that is, the reliability of the X-ray tube apparatus can be improved.

<Step structure>
FIG. 2 is a view for explaining an example of the recoil electron trajectory in the X-ray tube apparatus according to the first embodiment of the present invention, in particular, after being irradiated from the cathode 11 and recoiled on the surface of the rotating anode target 14. The trajectory of recoil electrons when absorbed and extinguished by other structural members is shown. In FIG. 2, one electron 31 is shown as an example of electrons (thermoelectrons) emitted from the cathode 11, but a large number of electrons are emitted from the cathode 11 to the rotating anode target 14 in actual electron beam irradiation. Is done.

  As is apparent from FIG. 2, the electrons (thermoelectrons) 31 emitted from the cathode 11 rotate in a trajectory indicated by a substantially straight arrow 35 so as to be orthogonal to the equipotential line 32 indicated by a dotted line in FIG. Collides with the anode target 14. Due to the collision of the electron beam, the rotary anode target 14 generates X-rays from the X-ray focal point and is irradiated as an X-ray beam. At this time, the rotating anode target 14 is irradiated with a large amount of electron beams, so that the rotating anode target 14 is in a high temperature state.

  On the other hand, about 50% of the electron beam irradiated to the rotating anode target 14 recoils on its surface, and collides with another structural member as a recoil electron, for example, in the trajectory indicated by the arrow 33. At this time, in the rotary anode target 14 according to the first embodiment, the step 23 for capturing recoil electrons is formed between the electron beam collision surface and the fin structure 21. About 10 to 20% of recoil electrons recoiled on the surface of 14 are absorbed by the step 23 and converted into heat. As a result, it is possible to suppress the generation of X-rays (unnecessary X-rays) generated when recoil electrons again enter the electron beam collision surface of the rotating anode target 14.

  However, the shape of the step 23 is set so that the edge does not stand in consideration of the influence on the discharge. Furthermore, the surface on which the step 23 is formed may be either the inclined surface or the planar portion of the rotating anode target 14 and is arranged so as to be hidden by the shadow of the recoil electron capturing structure 12. By disposing in this manner, discharge outside the focal plane between the cathode 11 and the rotary anode target 14 can be suppressed. That is, when the step 23 and the cathode 11 are connected by a straight line, the step 23 is formed so that the recoil electron capturing structure 12 is arranged on the straight line.

  In the X-ray tube apparatus according to the first embodiment, the rotary anode target 14 and the vacuum envelope 2 have the fin structures 21 and 22, respectively. Is efficiently radiated from the fin structure 21 to the fin structure 22, and the heat radiated to the fin structure 22 is transmitted from the wall surface of the vacuum envelope 2 to the refrigerant. That is, the heat generated at the X-ray focal point of the rotary anode target 14 is directly radiated from the X-ray focal point position, and the entire rotary anode target 14 and the rotary anode connected to the rotary anode target 14 by heat conduction. Heat is also transferred to the support structure 15 and the rotation support mechanism 16 and the like, and heat is radiated from each part.

  Further, the heat generated at the X-ray focal point is also transferred to the fin structure 21 formed at the rotation center axis portion of the rotary anode target 14 by heat conduction. At this time, since the fin structure 21 has a configuration in which a plurality of cylinders are arranged, the surface area of the fin structure 21 is large, and the radiant heat from the fin structure 21 is large. In addition, since the fin structure 22 arranged to face the fin structure 21 has a configuration in which a plurality of cylinders are arranged, the surface area of the fin structure 22 is large. Therefore, heat generated at the X-ray focal point of the rotary anode target 14 can be efficiently transferred from the side wall portion of the vacuum envelope 2 to the refrigerant through the fin structure 21 through the fin structure 22. The temperature increase of the rotating anode target 14 accompanying the recoil electron capture can be greatly suppressed.

  Further, among the recoil electrons not shown by the arrows in FIG. 2, the recoil electrons directed toward the rotation center axis of the rotating anode target 14 according to the equipotential line 32 shown by the dotted line are the fin structure 21 or the fins. It will collide with any of the cylindrical fins provided in the structure 22. As a result, in the X-ray tube apparatus of the first embodiment, recoil electrons can be prevented from directly heating the vicinity of the rotation center axis of the rotary anode target 14. Therefore, in the X-ray tube apparatus of the first embodiment, it is possible to obtain a special effect that heating of a bearing (not shown) constituting the rotation support mechanism 16 due to the rotation support mechanism 16 being directly heated can be suppressed. It becomes possible. In particular, as a bearing (not shown) constituting the rotation support mechanism 16, a rolling bearing such as a ball bearing or a hydrodynamic slide bearing in which a groove is formed on the rotating shaft surface and a liquid metal lubricant is filled in the bearing gap is used. Therefore, the effect of reducing the heat load on the bearing portion is great.

  As described above, in the X-ray tube apparatus according to the first embodiment, the fin structure 21 is formed on the rotating anode target 14 and the region closer to the fin structure 21 than the electron beam collision position of the rotating anode target 14 is formed. The step 23 for capturing recoil electrons is formed. By adopting such a structure, it becomes possible to efficiently capture recoil electrons and efficiently suppress the temperature rise of the rotating anode target 14 accompanying the capture of recoil electrons. Furthermore, in the X-ray tube apparatus according to the first embodiment, the fin structure 22 is formed on the inner wall surface of the vacuum envelope 2 facing the electron beam collision surface of the rotating anode target 14. The radiant heat from the fin structure 21 formed on the rotary anode target 14 can be efficiently transferred to the vacuum envelope 2. As a result, the rotating anode target 14 can be efficiently cooled. That is, since the temperature rise of the rotary anode target 14 can be suppressed, the temperature rise of the rotary anode support structure 15 and the rotary support mechanism 16 to which the rotary anode target 14 is connected can also be suppressed.

  In the X-ray tube apparatus according to the first embodiment, the fin structure 21 and the fin structure 22 serving as heat exchange means for transferring the heat of the rotating anode target 14 into the vacuum region inside the vacuum envelope 2 are provided. By forming, it becomes the structure which improves the heat exchange efficiency in a vacuum.

  In the X-ray tube apparatus of the first embodiment, the fin structures 21 and 22 are provided in the rotary anode target 14 and the vacuum envelope 2, but the present invention is not limited to this, and either The structure which provides a fin structure may be sufficient. For example, even when the fin structure 21 is provided only on the electron beam irradiation surface side of the rotating anode target 14, recoil electrons that could not be captured by the recoil electron capturing structure 12, the step 23, etc. This is because the fin structure 21 can significantly reduce the vicinity of the rotation center axis 14. Furthermore, by providing the fin structure 21, the surface area of the rotating anode target 14 can be significantly increased, so that it is possible to radiate radiant heat efficiently and heat dissipation performance is improved. Further, the shape of the fin structure 21 at this time is not limited to the concentric cylindrical shape because the opposing surface is the inner wall surface of the vacuum envelope 2, and can be any irregular shape. .

  On the other hand, even when the fin structure 22 is provided only on the inner wall surface side of the vacuum envelope 2, recoil electrons that could not be captured by the recoil electron capturing structure 12, the step 23, etc. This is because the fin structure 22 can significantly reduce the vicinity of the rotation center axis. Furthermore, since the area of the inner wall surface of the vacuum envelope 2 can be greatly increased by providing the fin structure 22, the radiant heat emitted from the rotating anode target 14 can be efficiently absorbed. Therefore, it is possible to suppress the temperature rise of the rotary anode target 14. Also in this case, since the opposing surface becomes the disk-shaped rotary anode target 14, the shape of the fin structure 22 may be an arbitrary uneven shape.

  In the X-ray tube apparatus according to the first embodiment, the step 23 is provided on the electron beam irradiation surface side of the rotating anode target 14 and the step 23 efficiently captures recoil electrons. However, the present invention is limited to this. There is nothing. For example, as shown in FIG. 8, even in the configuration in which only the step 23 formed on the rotary anode target 14 of Embodiment 1 is removed, recoil electrons are captured near the rotation center axis by the fin structures 21 and 22. Therefore, the heating of the rotating anode support structure 15 can be suppressed, and heat exchange from the fin structure 21 to the fin structure 22 can be performed efficiently. Therefore, the rotating anode target 14 and the rotating anode support structure 15 Temperature rise can be suppressed.

  Furthermore, in the X-ray tube apparatus according to the first embodiment, the case where the fin thickness forming the fin structure 22 is thinner than the fin thickness forming the fin structure 21 has been described. Instead, the fin thickness forming the fin structure 22 may be thicker. However, since the thickness of each fin is preferably a shape with high cooling efficiency, so-called fin efficiency (= [actual amount of heat transferred] / [transmitted assuming that the total surface area of the fin is equal to the base temperature of the fin) A shape with a high heat quantity]) is desirable. Such a shape can be realized by designing the fin in consideration of heat conduction to the fin and radiation of heat from the fin.

<Embodiment 2>
FIG. 3 is a cross-sectional view for explaining a schematic configuration of an X-ray tube apparatus according to Embodiment 2 of the present invention. Hereinafter, an overall configuration of the X-ray tube apparatus according to Embodiment 2 will be described with reference to FIG. However, the X-ray tube apparatus of the second embodiment is different only in the method of forming the fin structure 21 formed on the rotary anode target 14 and the configuration without providing a step, and the other configuration is the X-ray tube apparatus of the first embodiment. It becomes the same composition as. Therefore, in the following description, the configuration of the fin structure 21 will be described in detail.

  As shown in FIG. 3, in the X-ray tube apparatus of the second embodiment, the fin structure 21 is formed by forming a plurality of concentric grooves formed around the rotation center axis of the rotary anode target 14. It is the composition to do. That is, in the X-ray tube apparatus of the second embodiment, the positions of the fins (convex portions) of the fin structure 22 and the groove portions (concave portions) 24 of the fin structure 21 coincide with each other. The part is designed to enter. By adopting such a configuration, the region formed between adjacent groove portions 24 formed in the fin structure 21 (the apparent fins (convex portions) of the fin structure 21) causes the fin structure 22 to be formed. The region is formed between adjacent fins to be formed (apparent groove portion (concave portion) of the fin structure 22).

  With the above configuration, the peripheral surface of the region (the apparent fin (convex portion) of the fin structure 21) formed between the adjacent groove portions 24 formed in the fin structure 21 and the fin structure 22 are formed. The fin peripheral side surface to be arranged is arranged to face. Therefore, as in the first embodiment, heat conduction from the fin structure 21 to the fin structure 22 can be performed efficiently.

  Even in the X-ray tube apparatus of the second embodiment, the fin structure 21 and the fin structure 22 cause recoil electrons to collide near the rotation center axis on the electron beam collision surface side of the rotating anode target 14. Therefore, as in the first embodiment, it is possible to suppress the temperature rise of the rotating anode support structure 15 and the rotation support mechanism 16.

  Furthermore, since the X-ray tube apparatus of the second embodiment is more likely to capture recoil electrons by the fin structure 22 than the first embodiment, it is possible to obtain a special effect that the cooling efficiency can be improved.

<Embodiment 3>
FIG. 4 is a cross-sectional view for explaining a schematic configuration of an X-ray tube apparatus according to Embodiment 3 of the present invention. Hereinafter, an overall configuration of the X-ray tube apparatus according to Embodiment 3 will be described with reference to FIG. However, in the X-ray tube apparatus of the third embodiment, only the shape of the fins forming the fin structure 21 formed on the rotary anode target 14 and the configuration without the step are different, and the other configurations are the same as those of the first embodiment. The configuration is the same as that of the tube apparatus. Therefore, in the following description, the configuration of the fin structure 21 will be described in detail.

  As is apparent from FIG. 4, in the X-ray tube apparatus according to the third embodiment, among the fins forming the fin structure 21 provided in the rotating anode target 14, the fin formed on the outermost periphery is on the fin structure 22 side. And a shape protruding in the outer peripheral direction of the rotary anode target 14. That is, in the fin structure 21 of the third embodiment, the fins arranged on the outermost periphery are formed continuously from the protrusion parallel to the rotation axis direction of the rotary anode target 14 and the rotation of the rotary anode target 14. It is comprised from the annular part orthogonal to an axial direction. However, the annular portion is not limited to a shape orthogonal to the rotation axis direction of the rotary anode target 14, and the formation angle can be arbitrarily set. That is, the shape of the fin arranged on the outermost periphery is made more complicated than the fin shape of the first embodiment.

  By providing such a fin structure 21, in addition to the effects in the X-ray tube apparatus of the first embodiment described above, the recoil electron capture efficiency by the fins arranged on the outermost periphery is improved in the X-ray tube apparatus of the first embodiment. It is possible to obtain a special effect that it can be improved. As a result, secondary and tertiary recoil electrons can be reduced as compared with the X-ray tube apparatuses of Embodiments 1 and 2, and generation of unnecessary X-rays can be further reduced.

  Furthermore, since it is the structure which makes the surface area of a fin increase and makes the opposing surface direction into the inner wall surface direction of the vacuum envelope 2, it becomes possible to improve the thermal radiation effect. As a result, in addition to the effect in the X-ray tube apparatus of Embodiment 1, the special effect that heat dissipation performance can be further improved is obtained.

<Embodiment 4>
FIG. 5 is a cross-sectional view for explaining a schematic configuration of an X-ray tube apparatus according to Embodiment 4 of the present invention. Hereinafter, an overall configuration of the X-ray tube apparatus according to Embodiment 4 will be described with reference to FIG. However, in the X-ray tube apparatus of the fourth embodiment, only the configuration of the cathode 51 and the configuration of the recoil electron capturing structure 52 that covers the cathode 51 and the configuration of the fin structure 21 that are clearly shown in FIG. Other basic configurations are the same as those of the X-ray tube apparatus of the second embodiment. Therefore, in the following description, the configuration of the cathode 51, the configuration of the recoil electron capturing structure 52, and the configuration of the fin structure 21 will be described in detail. The configurations of the cathode 51 and the recoil electron capturing structure 52 of the fourth embodiment can be applied to other embodiments.

  As apparent from FIG. 5, in the X-ray tube apparatus of the fourth embodiment, the region far from the irradiation side of the X-ray beam irradiated from the rotating anode target 14 (the right region in FIG. 5), that is, the rotating anode target 14. The recoil electron capturing structure 52 is formed only in a region far from the rotation center axis. By adopting such a configuration, in the X-ray tube apparatus according to the fourth embodiment, the configuration of the recoil electron capturing structure 52 is simplified, and the size of the recoil electron capturing structure 52 is reduced as the mounting space is reduced. , And the weight of the X-ray tube apparatus main body can be reduced.

  In the X-ray tube apparatus of the fourth embodiment, the shape of the cathode 51 is inclined in the direction of the rotation center axis of the rotary anode target 14. With this configuration, as will be described in detail later, the distribution of the electric field generated between the cathode 51, the recoil electron capturing structure 52, and the rotating anode target 14 is changed, and the electron beam emitted from the cathode 51 is reflected. It is configured to prevent it from being captured by the recoil capturing structure 52. Furthermore, even in the shape of the fin 53 formed on the outermost periphery among the plurality of fins forming the fin structure 21, the protrusion amount and shape greatly affect the electric field distribution. The fin structure 21 of No. 4 is configured to hold the electric field distribution in an optimum state by adopting a configuration described in detail later.

  As described above, also in the X-ray tube apparatus of the fourth embodiment, the fin structure 21 is formed on the electron beam collision surface side of the rotary anode target 14 and the vacuum envelope 2 facing the fin structure 21 is provided. Since the fin structure 22 is formed on the inner wall surface, it is possible to obtain the effects of the X-ray tube apparatus of the first embodiment described above.

  Next, FIG. 6 is a diagram for explaining an example of the potential distribution and recoil electron trajectory between the cathode and recoil electron capturing structure and the rotating anode target in the X-ray tube apparatus according to Embodiment 4 of the present invention. Hereinafter, the effect of reducing recoil electrons will be described with reference to FIG. 6 also shows one electron 31 as an example of electrons (thermoelectrons) emitted from the cathode 11 as in FIG. 2 described above. However, in actual irradiation with an electron beam, many electrons are emitted from the cathode 11. The light is emitted to the rotating anode target 14.

  In the X-ray tube apparatus of the fourth embodiment, the recoil electron capturing structure 52 is provided only on the X-ray beam irradiation side. In this case, the electric field distribution around the cathode 51 is greatly different between the side where the recoil electron capturing structure 52 is formed and the side where it is not formed. That is, as shown in the region surrounded by the round frame in FIG. 6, the electric field between the cathode 52 and the recoil electron capturing structure 52 is increased on the side where the recoil electron capturing structure 52 is formed. By this electric field, recoil electrons are easily collected between the recoil electron capturing structure 52 and the cathode 51 of Embodiment 4, and the recoil electron capturing structure 52 efficiently captures recoil electrons.

  Furthermore, in the recoil electron capturing structure 52 of Embodiment 4, the electric field distribution indicated by the equipotential lines 32 along the curved surface is formed by making the surface on the rotating anode target 14 side a curved surface. . With this configuration, the recoil electrons that recoil again among the recoil electrons colliding with the recoil electron capturing structure 52 are greatly reduced.

  At this time, in the cathode 51 of the fourth embodiment, the shape of the top of the head is different on the side closer to the recoil electron capturing structure 52 and on the far side. That is, by forming an inclination at the top of the cathode 51 from the side closer to the recoil electron capturing structure 52 toward the side farther, the emission angle of electrons emitted from the cathode 51 is changed, and irradiation from the cathode 51 is performed. The electron beam is prevented from being captured by the recoil electron capturing structure 52.

  Furthermore, in the X-ray tube device of Embodiment 4, the X-ray tube device is formed on the outermost periphery of the fin structure 21 in order to efficiently capture recoil electrons that recoil to the side where the recoil electron capture structure 52 is not formed. The fin 53 is used.

  As described above, in the X-ray tube apparatus according to the fourth embodiment, the cathode 51, the recoil electron capturing structure 52, the rotating anode target 14, and the fin structure 21 are operated to obtain a desired electric field distribution. ing. That is, in the X-ray tube apparatus of the fourth embodiment, recoil electrons are captured by the recoil electron capturing structure 52 that is a structure, and recoil electrons are captured by the fin structure 21 and the fin structure 22 that are structures. In addition to direct shielding, by providing irregularities and appropriate shapes on the electron beam collision surface of the rotating anode target 14 and in the vicinity thereof, and also in the vicinity of the cathode 51, an electric field distribution suitable for capturing recoil electrons can be obtained. In this configuration, recoil electrons are not scattered toward the center of the rotary anode axis.

  Furthermore, recoil electrons can be guided in a desired direction by changing the shape of each structure to form an electric field distribution. Such an electric field distribution is formed by the shape of the recoil electron capturing structure (collector) 52, the shape of the rotating anode target 14 on the electron collision surface side, the shape of the surface facing it, the shape of the cathode 51, and the electron emission. This is possible by combining the angle to be formed and the shape of the focusing body (not shown).

  In this way, by applying the present invention, the recoil electron capturing structure (collector) 52 that has conventionally been required to have a cylindrical shape, such as a semi-cylinder, is centered on the anode rotation target with reference to the focal plane. Only the opposite direction, that is, the structure outside the X-ray tube 1 is sufficient. With this structure, since the recoil electron capturing structure 52 is formed only in a portion close to the tube container 18, it is possible to obtain a special effect that the recoil electron capturing structure 52 can be easily cooled.

<Embodiment 5>
FIG. 7 is a cross-sectional view for explaining a schematic configuration of an X-ray tube apparatus according to Embodiment 5 of the present invention. Hereinafter, an overall configuration of the X-ray tube apparatus according to Embodiment 5 will be described with reference to FIG. However, in the X-ray tube apparatus according to the fifth embodiment, the configurations of the rotary support mechanisms 16 and 71, the fin structures 21 and 22 and the rotary anode support structure 15 that constitute the double-supported bearing that supports the rotary anode target 14 are excluded. Other configurations are the same as those of the X-ray tube apparatus of the fourth embodiment. Therefore, in the following description, the configurations of the rotation support mechanisms 16 and 71, the fin structures 21 and 22, and the rotation anode support structure 15 that constitute the both-end bearing that supports the rotation anode target 14 will be described in detail. Note that the configurations of the rotation support mechanisms 16 and 71, the fin structures 21 and 22 and the rotation anode support structure 15 of the fifth embodiment can be applied to the other first to third embodiments.

  As is clear from FIG. 7, the X-ray tube apparatus according to the fifth embodiment includes a rotating anode support structure 15 that penetrates the rotating anode target 14, and is illustrated at one end of the rotating anode support structure 15. The rotation support mechanism 16 including a non-rotating rotor is disposed, and the rotation support mechanism 71 is disposed at the other end. That is, in the X-ray tube apparatus of the fifth embodiment, a configuration of a so-called double-supported bearing in which the rotation support mechanism 16 is disposed on one end side and the rotation support mechanism 71 is disposed on the other end side via the rotating anode target 14. It has become. The rotation support mechanisms 16 and 71 may be any of a well-known rolling bearing method and a sliding bearing such as a fluid bearing. In the X-ray tube apparatus of the fifth embodiment, the rotation support mechanism 15 is disposed on the back surface side of the rotary anode target 14 and the rotation support mechanism 15 is disposed on the electron beam irradiation surface side of the rotation anode target 14. It has become.

  In the fifth embodiment, since the rotary anode support structure 15 is disposed so as to penetrate the rotary anode target 14, the rotary anode support structure is also used in the fin structures 21 and 22 of the fifth embodiment. A plurality of fins forming the fin structures 21 and 22 are arranged in the outer peripheral area of the rotating anode support structure 15 that is an area avoiding the area where the body 15 is arranged.

  Therefore, in the conventional configuration, recoil electrons directly reach the rotating anode support structure 15 and directly heat the rotating anode support structure 15. However, in the X-ray tube apparatus of the fifth embodiment, the rotating anode support structure 15 rotates. Fin structures 21 and 22 formed on the outer peripheral portion of the anode support structure 15 are configured to prevent recoil electrons from reaching the rotating anode support structure 15. As a result, it is possible to prevent recoil electrons from being directly captured by the rotating anode support structure 15 and heating the rotating anode support structure 15, in addition to the effects of the first embodiment described above. Thus, a special effect that the temperature rise of the rotating anode support structure 15 can be further suppressed can be obtained.

<Embodiment 6>
FIG. 9 is a diagram for explaining a schematic configuration of an X-ray CT apparatus according to Embodiment 6 of the present invention. The X-ray CT apparatus shown in FIG. 9 has the same configuration as the conventional X-ray CT apparatus except for the X-ray tube apparatus 901. The applicable range of the X-ray tube apparatus of the present invention is not limited to the X-ray CT apparatus, and can be applied to other X-ray imaging apparatuses.

  As is apparent from FIG. 9, the X-ray CT apparatus according to the sixth embodiment is disposed opposite to the X-ray tube apparatus 901 according to any one of the first to fifth embodiments that generates an X-ray beam. An imaging system is formed with the X-ray detector 902. The photographing system is housed in a rotating body 903 and is rotated at a high speed together with the rotating body 903. Further, the rotating body 903 is configured to accommodate the power supplies 904 and 905 and the weight 906. The rotating body 903 is rotatably attached to a casing 907 standing on the floor, and is rotated at a high speed by a motor 908 so that rotational imaging can be performed from 360 degrees around a subject 912 mounted on a mount 909. Yes.

  An X-ray image taken from 360 degrees around the subject 912 is subjected to a known reconstruction calculation or the like by the image processing apparatus 910 to generate a tomographic image, a three-dimensional image, or the like of the subject 912, and Is displayed.

  At this time, since the X-ray CT apparatus of the sixth embodiment is configured to use the X-ray tube apparatus of the first to fifth embodiments of the present invention, a large amount of X-ray beams can be output for a long time. As a result, the time required for scanning (CT imaging) of the subject 912 can be shortened, and a reconstructed image with reduced motion artifacts can be obtained even for a relatively fast organ such as the heart. .

  In addition, since the time required for scanning (CT imaging) of the subject 912 can be shortened, the burden on the subject 912 can be reduced, and X-ray CT imaging of more subjects can be performed. Can do.

  Further, by using the X-ray tube apparatus of Embodiments 4 and 5, the weight of the X-ray tube apparatus 901 can be reduced and the load applied to the rotating body 903 can be reduced, so that the rotating body 903 (imaging system) can be mounted at higher speed. It is possible to rotate, and further shorten the photographing time.

  Furthermore, since the X-ray tube apparatus of Embodiments 1 to 5 is used, the mechanical reliability of the X-ray CT apparatus body can be improved.

  In the X-ray tube apparatus according to the first to fifth embodiments of the present invention, the fin structure 22 arranged on the inner wall surface of the vacuum envelope 2 is more electron beam than the fin structure 21 arranged on the rotating anode target 14. Although it is set as the structure close | similar to a collision surface, it is not limited to this. For example, by arranging fins (convex portions) forming the fin structure 22 arranged on the inner wall surface of the vacuum envelope 2 on the outermost peripheral side, the rate of recoil electrons reaching the fin structure 22 is increased. Therefore, it is possible to suppress an increase in the temperature of the rotating anode target 14 due to recoil electrons, and to obtain a special effect that the heat radiation performance of the entire X-ray tube apparatus can be improved. It becomes.

  In the X-ray tube apparatus according to the first to fifth embodiments of the present invention, the fin structure 21 is formed by providing a step having a cylindrical uneven shape corresponding to the convex fin of the fin structure 22. It is not limited to this. For example, it is possible to reduce the weight of the fin structure 21 by forming a defect region extending from the top to the bottom of the fin as a notch in a part of the fin structure 21.

  Furthermore, in the X-ray tube apparatus according to the first to fifth embodiments of the present invention, the case where a plurality of fins forming the fin structure 21 and the fin structure 22 are formed has been described. May be 1 or more.

  Furthermore, in the X-ray tube apparatus according to the first to fifth embodiments of the present invention, corner portions are provided as the uneven portions provided in the vicinity of the central axis of the rotary anode target 14 and the uneven portions provided on the opposing wall surface of the vacuum envelope 2. The fin structure 21 and the fin structure 22 are provided. However, the present invention is not limited to the above-described shape, and may be a gentle concavo-convex shape formed in a curved shape on the concave portion and the convex portion.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment of the invention. However, the invention is not limited to the embodiment of the invention, and various modifications can be made without departing from the scope of the invention. It can be changed.

DESCRIPTION OF SYMBOLS 1 ... X-ray tube apparatus, 2 ... Vacuum envelope, 11, 51 ... Cathode 12, 52 ... Recoil-electron capture structure (collector), 13 ... Radiation window 14 ... Rotating anode target, 15 ...... Rotary anode support structure 16, 71 ... Rotation support mechanism, 17 ... Stator, 21, 22 ... Fin structure 23 ... Step, 24 ... Groove, 31 ... Electron, 32 ... Equipotential line 33, 34 ... Arrow (recoil electron orbit), 35 ... Arrow (electron beam orbit)
53 ... Fins on the outermost periphery, 901 ... X-ray tube device, 902 ... X-ray detector 903 ... Rotating body, 904, 905 ... Power source, 906 ... Weight, 907 ... Housing 908 ... Motor , 909... Mount, 910... Image processing device, 911... Monitor 912.

Claims (5)

A cathode that emits an electron beam; an anode target that collides the electron beam and generates X-rays with the collided position as a focal position; a rotating mechanism that rotates the anode target; the cathode and the anode target An X-ray tube device comprising an envelope that holds the vacuum in a vacuum,
An X-ray tube apparatus comprising: a first uneven portion formed on an inner wall surface side of the envelope and protruding toward an electron beam collision surface side of the anode target. The X-ray tube apparatus according to claim 1,
A region on the electron beam collision surface side of the anode target, further comprising a second concavo-convex portion that is formed in a region excluding at least the electron beam collision region and protrudes toward the inner wall surface side of the envelope ;
The X-ray tube apparatus characterized in that the first uneven portion and the second uneven portion are arranged in combination with each other. The X-ray tube apparatus according to claim 2,
An X-ray tube apparatus comprising a step between the second uneven portion and the electron beam collision region. 3. The X-ray tube apparatus according to claim 2, wherein a portion formed on the outermost periphery of the second concavo-convex portion has a shape protruding in an outer peripheral direction of the anode target. The X-ray tube apparatus according to any one of claims 1 to 4, which irradiates a subject with X-rays;
An X-ray detector that is disposed opposite to the X-ray tube device and detects X-rays transmitted through the subject;
A scanner mounted with the X-ray tube device and the X-ray detector and rotating around the subject;
A data collection unit for collecting projection data detected by the X-ray detector for each of the two focal positions;
An image reconstruction device for reconstructing a tomographic image of the subject based on the projection data collected by the data collection unit;
An X-ray CT apparatus comprising: an image display device that displays a tomographic image reconstructed by the image reconstruction device.

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