X-ray tube system and X-ray CT system

Abstract

To provide a lightweight X-ray tube device and an X-ray CT device equipped with the same.SOLUTION: An X-ray tube device includes a cathode that generates an electron beam, an anode that emits X-rays upon collision with the electron beam, an X-ray tube including an envelope that holds the cathode and the anode in a vacuum atmosphere and an X-ray window provided in the envelope for irradiating a subject with a part of the X-rays emitted from the anode, and a tube container in which the X-ray tube is sealed together with insulating oil, and further includes a protective member provided on an outer wall of the envelope at least around the radiation window and shielding the X-rays.SELECTED DRAWING: Figure 2

Description

Technical Field

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[0001] The present invention relates to an X-ray tube device and an X-ray CT (Computed Tomography) device, and particularly to the protective lead provided in the X-ray tube device.

Background Art

[0002] <000-0009>An X-ray CT device generates a tomographic image of a subject by rotating an X-ray tube device that irradiates the subject with X-rays and an X-ray detector that detects the X-rays transmitted through the subject around the subject, and using the projection data obtained from multiple directions. The generated tomographic image depicts the shape of the organs in the subject and is used for image diagnosis.

[0003] An X-ray tube device includes an X-ray tube that holds a cathode and an anode in a vacuum, and a tube container that encloses the X-ray tube together with insulating oil. By colliding an electron beam emitted from the cathode and accelerated by a high voltage applied between the cathode and the anode with an X-ray focal point on the anode, X-rays are emitted from the X-ray focal point. Among the X-rays emitted from the X-ray focal point, the X-rays other than those irradiated on the subject cause ineffective exposure, so it is necessary to prevent the leakage of such X-rays.

[0004] Patent Document 1 discloses an X-ray tube device in which a protective lead for preventing X-ray leakage is attached to the inner wall of the tube container.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, Patent Document 1 does not adequately consider weight reduction for X-ray tube devices. Specifically, because the surface area of ​​the inner wall of the tube container is relatively large, a large amount of protective lead is attached to the inner wall. Furthermore, in recent years, with the increase in the amount of X-rays required for X-ray CT devices, the weight of the anode has been increasing, so it is necessary to lighten components other than the anode.

[0007] Therefore, the present invention aims to provide a lightweight X-ray tube device and an X-ray CT device equipped therewith. [Means for solving the problem]

[0008] To achieve the above objective, the present invention provides an X-ray tube apparatus comprising: a cathode that generates an electron beam; an anode that emits X-rays when the electron beam collides with it; an enclosure that holds the cathode and the anode in a vacuum; an X-ray tube provided in the enclosure and having a radiation window for emitting the X-rays toward a subject; and a tube container that seals the X-ray tube together with insulating oil, wherein the apparatus further comprises a protective member provided at least around the radiation window on the outer wall of the enclosure for shielding the X-rays.

[0009] Furthermore, the present invention is an X-ray CT apparatus for generating tomographic images of a subject, characterized in that it comprises the aforementioned X-ray tube apparatus. [Effects of the Invention]

[0010] According to the present invention, a lightweight X-ray tube apparatus and an X-ray CT apparatus equipped therewith can be provided. [Brief explanation of the drawing]

[0011] [Figure 1] This diagram shows the overall configuration of an X-ray CT scanner. [Figure 2] This figure shows an example of the overall configuration of an X-ray tube apparatus. [Figure 3] This figure shows an example of the configuration of a protective component. [Figure 4] This figure shows an example of the configuration of a protective component. [Figure 5]This figure shows an example of the configuration of a protective component. [Figure 6] This figure shows an example of the configuration of a protective component. [Figure 7] This figure shows an example of the configuration around the X-ray window. [Figure 8] This figure shows an example of the configuration around the X-ray window. [Modes for carrying out the invention]

[0012] Preferred embodiments of the X-ray tube apparatus and X-ray CT apparatus according to the present invention will be described below with reference to the attached drawings. In the following description and attached drawings, components having the same functional configuration will be denoted by the same reference numerals to avoid redundant explanations.

[0013] An example of the overall configuration of the X-ray CT apparatus 1 will be explained using Figure 1. The X-ray CT apparatus 1 comprises a scan gantry unit 100 and an operating unit 120. The scan gantry unit 100 comprises an X-ray tube device 101, a rotating disk 102, a collimator 103, an X-ray detector 106, a data acquisition device 107, a patient table device 105, a gantry control device 108, a patient table control device 109, and an X-ray control device 110. The X-ray tube device 101 is a device that irradiates the subject 10 placed on the patient table device 105 with X-rays. The collimator 103 is a device that limits the irradiation range of the X-rays. The rotating disk 102 has an opening 104 into which the subject 10 placed on the patient table device 105 enters, and mounts the X-ray tube device 101 and the X-ray detector 106, rotating the X-ray tube device 101 and the X-ray detector 106 around the subject 10.

[0014] The X-ray detector 106 is positioned opposite the X-ray tube apparatus 101 and measures the spatial distribution of transmitted X-rays by detecting X-rays that have passed through the subject 10. The detection elements of the X-ray detector 106 are arranged in two dimensions: in the direction of rotation of the rotating disk 102 and in the direction of rotation axis. The data acquisition device 107 is a device that collects the amount of X-rays detected by the X-ray detector 106 as digital data. The gantry control device 108 is a device that controls the rotation and tilt of the rotating disk 102.

[0015] The bed control device 109 is a device that controls the up / down, front / back, left / right movement of the bed device 105. The X-ray control device 110 is a device that controls the power input to the X-ray tube device 101.

[0016] The operation unit 120 includes an input device 121, an image processing 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 the name of the subject 10, the examination date and time, imaging conditions, etc., and specifically includes a keyboard, a pointing device, a touch panel, etc. The image processing device 122 is a device that performs arithmetic processing on the measurement data sent from the data collection device 107 to reconstruct a CT image or perform various image processes on the CT image. The display device 125 is a device that displays the CT image and the like generated by the image processing device 122, and specifically includes a liquid crystal display, a touch panel, etc. The storage device 123 is a device that stores the data collected by the data collection device 107, the CT image generated by the image processing device 122, etc., and specifically includes an HDD (Hard Disk Drive), etc. The system control device 124 is a device that controls each part.

[0017] Based on the imaging conditions input from the input device 121, particularly the X-ray tube voltage, X-ray tube current, etc., the X-ray control device 110 controls the power input to the X-ray tube device 101, so that the X-ray tube device 101 irradiates the subject 10 with X-rays corresponding to the imaging conditions. The X-ray detector 106 detects the X-rays irradiated from the X-ray tube device 101 and transmitted through the subject 10 with two-dimensionally arranged detection elements, and measures the distribution of the transmitted X-rays. The rotating disk 102 is controlled by the gantry control device 108 and rotates based on the imaging conditions input from the input device 121, particularly the rotation speed, etc. The bed device 105 is controlled by the bed control device 109 and operates based on the imaging conditions input from the input device 121, particularly the helical pitch, etc.

[0018] X-ray irradiation from the X-ray tube device 101 and X-ray measurement by the X-ray detector 106 are repeated along with the rotation of the rotating disk 102, so that projection data from various angles is acquired, and the acquired projection data is transmitted to the image processing device 122. The image processing device 122 reconstructs a CT image by performing back-projection processing on the transmitted projection data from various angles. The reconstructed CT image is displayed on the display device 125.

[0019] Using FIG. 2, an example of the overall configuration of the X-ray tube device 101 will be described. The X-ray tube device 101 includes an X-ray tube 210 that generates X-rays and a tube container 220 that encloses the X-ray tube 210 together with insulating oil.

[0020] The X-ray tube 210 has a cathode 211, an anode 212, an envelope 213, and an X-ray window 218.

[0021] The cathode 211 generates an electron beam 216 and includes, for example, a filament or a cold cathode and a focusing electrode. The filament is a high-melting-point material such as tungsten wound in a coil shape, which is heated by flowing a current and emits electrons. The cold cathode is a metal material such as nickel or molybdenum sharpened, and electrons are emitted by field emission due to the concentration of an electric field on the cathode surface. The focusing electrode forms a focusing electric field for focusing the emitted electrons toward the X-ray focus on the anode 212. The filament or cold cathode and the focusing electrode are at the same potential.

[0022] The anode 212 has a positive potential applied thereto with respect to the cathode 211, and is, for example, disk-shaped and includes a target and an anode base material. The target is made of a high-melting-point and high-atomic-number material such as tungsten. When electrons emitted from the cathode 211 collide with the X-ray focus on the target, X-rays are emitted from the X-ray focus. The anode base material is made of a material with high thermal conductivity such as copper and holds the target. The target and the anode base material are at the same potential.

[0023] The enclosure 213 holds the cathode 211 and anode 212 in a vacuum atmosphere to electrically insulate them from each other. The potential of the enclosure 213 is the ground potential.

[0024] The X-ray window 218 is provided in the enclosure 213 to direct X-rays 217, which are a portion of the X-rays emitted from the X-ray focal point, toward the subject 10, and is made of a material with a low atomic number, such as beryllium. Since electrons emitted from the anode 212 collide with the X-ray window 218, the X-ray window 218 and its surroundings tend to become hot.

[0025] Electrons emitted from the cathode 211 are accelerated by the voltage applied between the cathode 211 and the anode 212 to form an electron beam 216. When the electron beam 216 is focused by a focusing electric field and collides with the X-ray focal point on the target, X-rays are emitted from the X-ray focal point. The energy of the emitted X-rays is determined by the voltage applied between the cathode and the anode, the so-called tube voltage, and the X-ray dose is determined by the amount of electrons emitted from the cathode, the so-called tube current, and the tube voltage.

[0026] Of the energy of the electron beam 216, only about 1% is converted into X-rays, with most of the remaining energy becoming heat. In the X-ray tube unit 101 installed in the medical X-ray CT scanner 1, the tube voltage is several hundred kV and the tube current is several hundred mA, so the anode 212 is heated with a heat energy of several tens of kilowatts. To prevent overheating and melting due to such heating, the anode 212 may be rotatable. For example, the anode 212 is rotatably supported by a rotating bearing 215 and rotates using the magnetic field generated by the excitation coil 214 as the rotational driving force. That is, as the anode 212 rotates, the X-ray focal point, which is the point where the electron beam 216 collides, is constantly moving, so the temperature of the X-ray focal point can be kept lower than the melting point of the target, and the anode 212 can be prevented from overheating and melting.

[0027] The tube container 220 encloses the X-ray tube 210 and the excitation coil 214, along with insulating oil that electrically insulates the X-ray tube 210 and serves as a cooling medium. The insulating oil is guided to a cooler through piping connected to the tube container 220, where it dissipates heat, and then returns to the tube container 220 through the piping. In other words, the insulating oil flows from one end of the tube container 220 to the other.

[0028] The tube vessel 220 is also provided with a radiation window 221 that emits X-rays 217. Like the X-ray window 218, the radiation window 221 is made of a material with a low atomic number, such as beryllium.

[0029] Since X-rays other than the X-rays 217 directed at the subject 10 result in ineffective exposure, protective members 219 are further provided around at least the X-ray window 218 on the outer wall of the enclosure 213 to shield against such X-rays. The protective members 219 are made of, for example, lead.

[0030] An example of the configuration of the protective member 219 will be explained using Figure 3. The protective member 219 illustrated in Figure 3 is a ring-shaped lead and is placed around the X-ray window 218. Since lead is a relatively soft material, it is held in place by a retaining member 300. The retaining member 300 is a stepped ring-shaped stainless steel member and is fixed to the enclosure 213 by screws 301.

[0031] As illustrated in Figure 3, by providing the protective member 219 at least around the X-ray window 218 on the outer wall of the enclosure 213, the amount of protective member 219 can be reduced compared to when it is provided on the inner wall of the tube container 220, thus enabling a lighter X-ray tube apparatus. It is desirable that the flow of insulating oil is not obstructed in and around the X-ray window 218, which tends to become hot.

[0032] An example of the configuration of a protective member 219, which is provided with a channel for insulating oil to flow, will be explained using Figure 4. The protective member 219 illustrated in Figure 4 is made of lead and has an annular shape, arranged around the X-ray window 218, similar to Figure 3, and is held by a SUS retaining member 300 which is fixed to the enclosure 213 by screws 301. The protective member 219 in Figure 4 is also provided with multiple grooves 400 that function as channels for insulating oil to flow between it and the outer wall of the enclosure 213. The insulating oil flows through the grooves 400 as shown by the arrows in Figure 4. A gap is provided between the protective member 219 and the X-ray window 218 so as not to obstruct the flow of insulating oil when it comes into contact with the X-ray window 218. Furthermore, since the lead protective member 219 may generate sludge that causes oil discharge due to reaction with the insulating oil, varnish may be applied to the surface of the protective member 219 to suppress sludge generation.

[0033] As illustrated in Figure 4, by providing grooves 400 in the protective member 219 that function as flow paths for insulating oil, the flow of insulating oil is not obstructed, and the X-ray window 218 and its surroundings can be cooled. Note that the flow path for insulating oil is not limited to grooves 400.

[0034] Using Figure 5, another example of the configuration of the protective member 219, which is provided with a flow path for insulating oil, will be described. The protective member 219 illustrated in Figure 5 is made of lead and has a rimmed cylindrical shape. It is positioned around the X-ray window 218 and held by a retaining member 300. The retaining member 300 in Figure 5 is a SUS (stainless steel) member that covers the outer wall of the protective member 219 and is fixed to the enclosure 213 by screws 301. On the sides of the protective member 219 and the retaining member 300, a pair of holes 500 that function as flow paths for insulating oil are provided parallel to the flow of insulating oil flowing from one end to the other of the tube container 220. The insulating oil flows in from one hole 500 as shown by the arrow in Figure 5, absorbs heat on the surface of the X-ray window 218, and then flows out from the other hole 500. A beryllium plate 501 may be provided at the lower end of the retaining member 300 to allow the insulating oil to flow smoothly over the surface of the X-ray window 218.

[0035] As illustrated in Figure 5, by providing holes 500 that function as flow paths for insulating oil on the sides of the protective member 219 and the holding member 300, the flow of insulating oil is not obstructed, and the X-ray window 218 and its surroundings can be cooled. Note that the shape of the holes 500 is not limited to that shown in Figure 5.

[0036] Another example of the configuration of the protective member 219, which is provided with a channel for insulating oil, will be described using Figure 6. The protective member 219 illustrated in Figure 6 is made of lead and has a rimmed cylindrical shape, positioned around the X-ray window 218, similar to Figure 5, and is held by a SUS retaining member 300 which is fixed to the enclosure 213 by screws 301. The sides of the protective member 219 and the retaining member 300 in Figure 6 are provided with a pair of holes 500 which function as channels for insulating oil to flow. However, the holes 500 are inclined with respect to the surface of the X-ray window 218 so as to guide the insulating oil flowing in from the holes 500 to the opposite surface of the electron collision region 600, which is the region where electrons emitted from the anode 212 collide with the X-ray window 218. More specifically, the holes 500 are inclined so that the extension of the central axis of the holes 500 intersects with the opposite surface of the electron collision region 600.

[0037] As illustrated in Figure 6, the holes 500 provided on the sides of the protective member 219 and the holding member 300 are inclined with respect to the surface of the X-ray window 218, thereby guiding the insulating oil to the opposite surface of the electron collision region 600 and further cooling the X-ray window 218.

[0038] Even if varnish is applied to the surface of the lead protective member 219, a small amount of sludge may be generated and adhere to the surface of the X-ray window 218. Sludge adhering to the surface of the X-ray window 218 hinders the cooling of the X-ray window 218 and becomes a source of noise in the X-ray image, so it is preferable to suppress the adhesion of sludge to the surface of the X-ray window 218.

[0039] Using the EE cross-sectional view in Figure 6, the protective member 219 that suppresses sludge adhesion to the surface of the X-ray window 218 will be described. The hole 500 illustrated in the EE cross-sectional view is provided so as to cause insulating oil to swirl along the inner surface of the cylindrical protective member 219. More specifically, the hole 500 is parallel to the flow of insulating oil flowing from one end to the other of the tube container 220, and is provided so as to be in contact with the inner surface of the protective member 219 at the point where the insulating oil flows into the protective member 219.

[0040] As illustrated in the EE cross-sectional view of Figure 6, holes 500 are provided along the inner surface of the cylindrical protective member 219 so as to allow insulating oil to swirl. The centrifugal force generated by the swirling of the insulating oil causes the sludge 601 to adhere to the inner surface of the protective member 219. As a result, sludge 601 does not adhere to the surface of the X-ray window 218.

[0041] Furthermore, the inner surface of the protective member 219 may be provided with irregularities 602 having a width and depth approximately the same as that of the sludge 601, which has an average particle size of 5 μm. By providing the irregularities 602 on the inner surface of the protective member 219, the sludge 601 that adheres to the inner surface of the protective member 219 due to centrifugal force will become trapped in the irregularities 602 and will not flow back into the insulating oil.

[0042] Figure 7 illustrates another example of the configuration around the X-ray window 218. As shown in Figure 7, a protective member 219 is provided around the X-ray window 218, similar to Figure 6, with a hole 500 that is inclined relative to the surface of the X-ray window 218. Furthermore, a slope 700 is provided on the inner wall of the tube container 220 to guide insulating oil toward the hole 500. More specifically, the slope 700 has an inclined surface along the extension of the central axis of the hole 500.

[0043] By providing the slope 700 illustrated in Figure 7, insulating oil is smoothly guided into the inclined hole 500 relative to the surface of the X-ray window 218, thereby enabling better cooling of the X-ray window 218.

[0044] Using Figure 8, another example of the configuration around the X-ray window 218 will be explained. In the X-ray window 218 illustrated in Figure 8, dimples are formed on its outer surface. When there are no dimples on the outer surface of the X-ray window 218, the peeling point 800, which is the point where insulating oil peels off from the outer surface of the X-ray window 218, is a point where the flow of insulating oil and the outer surface of the X-ray window 218 are parallel, and the stagnant region 801, where the flow of insulating oil stagnates, is relatively large. In contrast, when there are dimples on the outer surface of the X-ray window 218, the peeling point 800 moves downstream compared to when there are no dimples, and as the peeling point 800 moves, the stagnant region 801 becomes smaller, allowing the X-ray window 218 and its surroundings to be cooled more effectively.

[0045] Embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and the components can be modified and implemented without departing from the spirit of the invention. Furthermore, multiple components disclosed in the above embodiments may be combined as appropriate. For example, the protective member 219 illustrated in Figures 5 and 6 may be provided with the groove 400 shown in Figure 4. Moreover, some components may be removed from all the components shown in the above embodiments. [Explanation of symbols]

[0046] 1: X-ray CT scanner, 10: subject, 100: scan gantry unit, 101: X-ray tube unit, 102: rotating disk, 103: collimator, 104: aperture, 105: patient table unit, 106: X-ray detector, 107: data acquisition device, 108: gantry control unit, 109: patient table control unit, 110: X-ray control unit, 120: operation unit, 121: input device, 122: image processing device, 123: memory device, 124: system control device, 125: display Apparatus, 210: X-ray tube, 211: cathode, 212: anode, 213: enclosure, 214: excitation coil, 215: rotating bearing, 216: electron beam, 217: X-ray, 218: X-ray window, 219: protective member, 220: tube container, 221: radiation window, 300: holding member, 301: screw, 400: groove, 500: hole, 501: beryllium plate, 600: electron impact area, 601: sludge, 602: uneven area, 700: slope, 800: peeling point, 801: stagnant area

Claims

1. An X-ray tube having a cathode that generates an electron beam, an anode that emits X-rays when the electron beam collides with it, an enclosure that holds the cathode and the anode in a vacuum atmosphere, and an X-ray window provided in the enclosure for irradiating a portion of the X-rays emitted from the anode toward a subject, An X-ray tube apparatus comprising a tube container that encloses the aforementioned X-ray tube together with insulating oil, The enclosure, excluding the inner wall of the tube container, is further provided with protective members that shield the X-rays, at least around the X-ray window on the outer wall of the enclosure, The protective member is provided with a channel through which the insulating oil flows. The X-ray tube apparatus is characterized in that the flow path is a hole that guides the insulating oil to the surface of the X-ray window.

2. An X-ray tube apparatus according to claim 1, The X-ray tube apparatus is characterized in that the hole is inclined with respect to the X-ray window such that it guides the insulating oil to the opposite surface of the region where electrons emitted from the anode collide with the X-ray window.

3. An X-ray tube apparatus according to claim 2, An X-ray tube apparatus comprising a slope for guiding the insulating oil toward the hole, the slope further comprising an inclined surface along the extension of the central axis of the hole.

4. An X-ray tube apparatus according to claim 1, The protective member has a cylindrical shape that covers the periphery of the X-ray window. The X-ray tube apparatus is characterized in that the hole is provided parallel to the flow of the insulating oil, which flows from one end to the other of the tube container, so as to cause the insulating oil to swirl along the inner surface of the protective member, and is in contact with the inner surface of the protective member at the point where the insulating oil flows into the protective member.

5. An X-ray tube apparatus according to claim 4, An X-ray tube apparatus characterized in that the inner surface of the protective member has irregularities having a width and depth determined based on the average particle size of the sludge.

6. An X-ray tube having a cathode that generates an electron beam, an anode that emits X-rays when the electron beam collides with it, an enclosure that holds the cathode and the anode in a vacuum atmosphere, and an X-ray window provided in the enclosure for irradiating a portion of the X-rays emitted from the anode toward a subject, An X-ray tube apparatus comprising a tube container that encloses the aforementioned X-ray tube together with insulating oil, The enclosure, excluding the inner wall of the tube container, is further provided with protective members that shield the X-rays, at least around the X-ray window on the outer wall of the enclosure, The protective member is provided with a channel through which the insulating oil flows. The X-ray tube apparatus is characterized in that the flow path is a groove through which the insulating oil flows between the outer wall of the enclosure and the protective member.

7. An X-ray tube having a cathode that generates an electron beam, an anode that emits X-rays when the electron beam collides with it, an enclosure that holds the cathode and the anode in a vacuum atmosphere, and an X-ray window provided in the enclosure for irradiating a portion of the X-rays emitted from the anode toward a subject, An X-ray tube apparatus comprising a tube container that encloses the aforementioned X-ray tube together with insulating oil, The enclosure, excluding the inner wall of the tube container, is further provided with protective members that shield the X-rays, at least around the X-ray window on the outer wall of the enclosure, An X-ray tube apparatus characterized in that dimples are formed on the outer surface of the X-ray window.

8. An X-ray CT apparatus that generates tomographic images of a subject, An X-ray CT apparatus characterized by comprising an X-ray tube apparatus according to any one of claims 1, 6, or 7.

Images