JP3871654B2 - X-ray generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray generator that generates a small and thin X-ray beam that can be used in the fields of medical diagnosis and treatment.
[0002]
[Prior art]
An X-ray tube, which is a conventional X-ray generator, uses either a gas X-ray tube (cold cathode X-ray tube) that uses vacuum discharge as an electron source or a thermionic X-ray tube (coolidge tube).
The electron beam emitted from the hot cathode is focused by the Wehnelt electrode and focused on the anode surface to generate X-rays. As the anode material, tungsten, in the case of continuous X-rays, and iron, copper, molybdenum, and silver are often used in the case of characteristic X-rays, particularly when Kα rays are desired. X-rays generated by bremsstrahlung have a continuous spectrum regardless of the cathode material. The bremsstrahlung is an X-ray that is emitted when electrons travel through the material because its traveling direction is bent by the nucleus of the material (bremsstrahlung), and shows the property of continuous X-rays. Moreover, the radiation angle of this continuous X-ray becomes large. In the X-ray treatment, the thinner the X-ray, the more accurately the irradiation region can be irradiated. Therefore, it is necessary to appropriately narrow down the X-ray with a collimator. For this reason, the output of thin X-rays formed by X-rays being absorbed by the collimator is significantly reduced. Moreover, the conventional X-ray generator is large.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide a small X-ray generator that can efficiently generate an X-ray beam having an extremely narrow angle.
Still another object of the present invention is to provide a small X-ray generator capable of efficiently generating an X-ray beam having a very narrow angle depending on the therapeutic X-ray source or diagnostic X-ray source and application. It is to provide.
[0004]
[Means for Solving the Problems]
X-ray generator according to claim 1, wherein according to the invention in order to achieve the above object, a vacuum container, an electron source for generating a high-energy electron beams are arranged in the container,
An X-ray target disposed in the container and colliding with an electron beam from the electron source to generate X-rays on the back surface ;
It arranged a large number of uniform holes in the back of having the X-ray target, an X-ray guide for guiding the other surface by total reflection X-rays incident on the bore, and
An assembly similar to the assembly of the X-ray target and the X-ray guide is composed of an assembly of another X-ray target and an X-ray guide arranged in a column so that the holes correspond to each other.
[0005]
According to a second aspect of the present invention, there is provided the X-ray generator according to the first aspect, wherein an absorption electrode that transmits the X-rays that have passed through the X-ray guide and absorbs electrons is provided.
X-ray generator according to claim 3, wherein according to the invention, in the X-ray generator according to claim 1, wherein the material of the target is Au, W, Mo, Pt, 1 or 2 or more metals selected from Re metal It is a combination.
[0006]
X-ray generator according to claim 4, wherein according to the invention, in the X-ray generator according to claim 1, wherein, if the energy level of the electron beam is 10Mev from 1 MeV, the thickness of the target is 0.7 to 1. 4 mm, preferably approximately 1.0 mm.
When the thickness of the target exceeds the lower limit, the amount of transmitted electrons increases, and when the thickness exceeds the upper limit, X-ray emission to the back surface decreases.
X-ray generator according to claim 5, wherein according to the invention, in the X-ray generator according to claim 1, wherein, if the energy level of the electron beam is 10Mev from 1 MeV, the inner diameter of the honeycomb-shaped channel hole of the X-ray guide d is 0.1 to 0.4 mm, more preferably about 0.2 mm, the diameter D of the X-ray guide is 2 to 4 mm, more preferably about 2.8 mm, and the length L of the X-ray guide is 7 to 14 mm. Preferably it is about 10 mm.
When the lower limit of the length of the X-ray guide is exceeded, the amount of transmitted electrons increases, and when the upper limit is exceeded, the X-ray is totally reflected more than necessary.
[0007]
X-ray generator according to claim 6, wherein according to the invention, in the X-ray generator according to claim 1, wherein, when the energy level of the electron beam is 100Kev from 10 keV, the thickness of the target is 0.07 to 0. 14 mm, preferably about 0.1 mm.
When the thickness of the target exceeds the lower limit, the amount of transmitted electrons increases, and when the thickness exceeds the upper limit, X-ray emission to the back surface decreases.
The X-ray generation device according to claim 7 of the present invention is the X-ray generation device according to claim 1 , wherein the energy level of the electron beam is as low as 10 Kev to 100 Kev.
The inside diameter d of the honeycomb-shaped channel of the X-ray guide is 0.1 to 0.4 mm, more preferably about 0.2 mm, and the diameter D of the X-ray guide is 2 to 4 mm, more preferably about 2.8 mm. The length L of the line guide is 0.7 to 1.4 mm, more preferably about 1 mm.
When the lower limit of the length of the X-ray guide is exceeded, the amount of transmitted electrons increases, and when the upper limit is exceeded, the X-ray is totally reflected more than necessary.
[0008]
An X-ray generator according to an eighth aspect of the present invention is the X-ray generator according to the first aspect , wherein the material of the X-ray guide is Al and a large number of holes are manufactured by machining.
X-ray generator according to claim 9, wherein according to the invention, in the X-ray generator according to claim 1, the X-ray guide are those formed by bundling a plurality of metal pipes.
[0009]
In order to achieve the object, an X-ray generator according to claim 10 according to the present invention comprises:
A vacuum vessel;
An electron source disposed in the vessel for generating a fast electron beam;
An X-ray target disposed in the container and colliding with an electron beam from the electron source to generate X-rays on the back surface ;
Has uniform pores of several, has a plurality of large conical bore from the input opening and the output opening for receiving the X-rays emitted from the back of the X-ray target, the hole is arranged on a rear surface of the X-ray target An X-ray guide for guiding the X-rays incident on the hole to the other surface by total reflection; and
An assembly similar to the assembly of the X-ray target and the X-ray guide is composed of an assembly of another X-ray target and an X-ray guide arranged in a column so that the holes correspond to each other.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an apparatus according to the present invention will be described below with reference to the drawings.
First, a case where the energy of the electron beam is high from 1 Mev to 10 Mev will be described. FIG. 1 is a schematic diagram showing the basic configuration of an X-ray generator according to the present invention.
An electron source 2 for generating a high-speed electron beam is provided in the vacuum vessel 1. The electron source 2 is composed of an ultra-small cold cathode using carbon nanotubes proposed by the present inventor. A microwave with a high voltage is applied from the microwave source 7 between the ultra-small cold cathode and the target 3. The electron beam excited by the microwave collides with the target 3 at a high speed. X-rays are generated from the back surface of the target 3 by the collision of the electron beams. The generated X-ray repeats total reflection on the inner wall of the X-ray guide 4, passes through the electron trapping electrode 5, and is emitted to the outside. The electron trapping electrode 5 captures electrons when a part of the electron beam colliding with the target 3 passes through the target 3 and travels to reach the electron trapping electrode 5. On the other hand, the electron trapping electrode 5 has a function of transmitting the X-ray. As the material, beryllium metal is suitable.
[0011]
The X-ray guide 4 shown in FIG. 1 forms a large number of honeycomb-like holes in a metal member, as shown in FIG. This is performed by electric discharge machining. A hole with a smooth surface can also be formed by pushing a needle-shaped metal. In addition to machining the metal bulk in this way, it is also possible to bind and form metal tubes.
The X-ray guide 4 is disposed on the back surface of the X-ray target 3 and totally reflects X-rays incident on an arbitrary hole 4i inside the X-ray guide 4 by the inner wall of the hole 4i. FIG. 4 shows the reflection state in an enlarged manner for one arbitrary hole 4i. X-rays are totally reflected when the incident angle is large, that is, when the X-ray angle with the metal surface is small.
[0012]
Next, the generation state of the X-ray 33 when the high-speed electron beam 31 collides with the thin metal film target shown in FIG. 3 will be described. When the high-speed electron beam 31 supplied from the electron source collides with the target 32, X-rays are generated on the back surface of the target 32.
When a high-speed electron beam of about 10 MeV collides with a thin metal film target 32 having a thickness of about 0.1 mm, X-rays 33 are generated on the back surface of the metal film target.
If the thickness of the metal film target 32 is reduced, X-rays are strongly emitted in the back surface direction, and the radiation angle is reduced. On the other hand, some high-speed electron beams pass through the thin metal film target 32.
[0013]
The material of the target 33 is selected from Au, W, Mo, Pt, and Re, which are metals having a large atomic weight and having a high melting point, chemical stability, and thermal radiation.
Similarly, the material of the honeycomb-shaped X-ray guide is selected from Al, Au, W, Mo, Pt, and Re. In particular, since the hole of the honeycomb-shaped X-ray guide is several hundred microns or less, Al that can be easily processed by electric discharge machining can be used. At this time, in order to obtain a structure in which the heat dissipation characteristics of the Al metal are improved, a heat dissipation mechanism in close contact with the honeycomb-shaped X-ray guide is used. The electron trapping electrode 5 shown in FIG. 4 is a very thin metal plate, has a function of transmitting X-rays and capturing electrons, and uses a metal such as beryllium.
[0014]
In the X-ray generator described above, that make up the X-ray generator of a number of stages arranged in tandem two or more so as the same assembly and assembly of said X-ray target and an X-ray guide the hole corresponding.
A first embodiment of an X-ray generator configured with a target and an X-ray guide in a three-stage set will be described with reference to FIG. The inside of the vacuum vessel is provided with an electron source that is arranged in the vessel and generates a high-energy electron beam 51. A high-speed electron beam 51 from the electron source (not shown) disposed in the container collides with the first target plate 52.
A honeycomb-shaped first X-ray guide plate 53 having a large number of uniform holes is disposed on the back surface of the first target plate 52 that generates X-rays.
Further, a second target plate 54 that generates X-rays is disposed on the back surface of the honeycomb-shaped first X-ray guide plate 53. A honeycomb-shaped second X-ray guide plate 55 having a large number of uniform holes is disposed on the back surface of the second target plate 54.
Subsequently, a third target plate 56 is disposed on the back surface of the honeycomb-shaped second X-ray guide plate 55. A honeycomb-shaped third X-ray guide plate 57 having a large number of uniform holes is disposed on the back surface of the third target plate 56. In this way, the target and the X-ray guide are assembled in three stages. Finally, X-rays are transmitted, but an electrode 58 for collecting electron beams is arranged.
[0015]
Inside the vacuum vessel is an electron source that is arranged in the vessel and generates a high energy electron beam, and a high-speed electron beam 51 from the electron source arranged in the vessel collides with the first target 52. X-rays are generated on the back surface of the first target plate 52 of the thin metal film. The generated X-ray 11 is totally reflected by the wall surface of the honeycomb-shaped first X-ray guide plate 53 having a large number of uniform holes on the back surface of the first target plate 52, and proceeds downward in the figure. The X-ray 11 passes through the second target plate 54. The transmitted X-rays 12 totally reflect the wall surface of the second X-ray guide plate 55 having a honeycomb shape. The X-ray 12 passes through the third target plate 56. The transmitted X-rays 13 are totally reflected on the wall surface of the third X-ray guide plate 57, finally pass through the electrodes, and are extracted to the outside.
[0016]
As described with reference to FIG. 3, a part of the high energy electron beam passes through the first target plate 52 as it is. The passing electrons 9 collide with the next second target plate 54. X-rays are generated by this collision. The X-rays are totally reflected by the wall surface of the second X-ray guide plate 55 having a honeycomb shape, pass through the third target plate 56, and then radiated to the outside. However, a part of the high-speed electron beam colliding with the second target plate 54 passes through the second target plate 54 (electron beam 10) and collides with the third target plate 56 to generate X-rays.
[0017]
This X-ray is totally reflected on the wall surface of the honeycomb-shaped third X-ray guide plate 57 and radiates to the outside. If the high-speed electron beam collides with the first target plate 52, the second target plate 54, and the third target plate 56 sequentially, it is almost converted into X-rays. Here, by appropriately selecting the thickness of the target film, improvement in X-ray generation efficiency and improvement in X-rays with a narrow X-ray emission angle can be obtained.
[0018]
The components of the second embodiment of the present invention will be described below with reference to FIG. In this embodiment, the hole constituting the honeycomb has a conical surface.
Inside the vacuum vessel, there is an electron source that is arranged in the vessel and generates a high-energy electron beam, and a hollow donut-shaped high-speed electron beam (61 indicates the central axis) collides with the target 62. X-rays are generated on the back surface of the thin metal film target 62. The hole of the X-ray guide is composed of an input side opening for receiving X-rays and an output opening for emitting X-rays. The central portion of the X-ray guide has a structure of an X-ray guide wall 63 in which a metal portion 64 made of copper or the like is coated with tungsten. In particular, the X-ray guide structure forms a tube with a tapered input opening that is larger than the output opening. The generated X-ray 65 is totally reflected on the back surface of the target 62 by the X-ray guide wall surface. The reflected X-ray 66 is totally reflected again by the X-ray guide wall surface. The totally reflected X-ray 67 is taken out of the X-ray guide.
[0019]
The inner diameter of the input side opening for receiving X-rays is about 0.2 to 0.4 mm, and 0.2 mm is selected as a representative value. In addition, an inner diameter of about 0.05 mm of the output side opening for emitting X-rays is selected. When the energy level of the electron beam is 1 Mev to 10 Mev, the length of the X-ray guide is approximately 10 mm.
[0020]
A portion of the fast electron beam may pass through the target 62 and advance. In this case, the second target may be provided on the back surface of the output opening of the X-ray guide, and the X-ray guide may be configured in multiple stages. Here, by selecting the thickness of the target film to the above-described dimensions, the X-ray generation efficiency can be improved and X-rays with a narrow X-ray emission angle can be obtained. Except for the difference in the shape of the holes, the second embodiment is the same as the second embodiment described above, and a description thereof will be omitted.
[0021]
As described above, when the energy of the electron beam is high from 1 Mev to 10 Mev, it is used for radiation therapy. However, the energy level of the electron beam can be lowered from 10 Kev to 100 Kev and used for measurement.
The inside diameter d of the honeycomb-shaped channel of the X-ray guide is 0.1 to 0.4 mm, more preferably about 0.2 mm, and the diameter D of the X-ray guide is 2 to 4 mm, more preferably about 2.8 mm. The length L of the line guide is 0.7 to 1.4 mm, more preferably about 1 mm.
The target thickness is 0.01 mm or less, and acceleration of the electron beam is performed by a high voltage pulse or a microwave electric field, and the electron source can be performed using a field emitter or the like. Used for diagnosis and inspection.
[0022]
On the other hand, when the energy of the electron beam is as high as 1 to 10 Mev, the target thickness is 0.1 mm or less, and the electron beam is accelerated by a microwave electric field, and the electron source is a thermal electron gun or This can be done using carbon nanotubes. It is used for X-ray therapy as an application.
[0023]
【The invention's effect】
The X-ray generator according to the present invention can generate a small-diameter X-ray beam having a small size and high parallelism.
The X-ray generator according to the present invention can be used as an X-ray source for intensity-modulated radiation therapy IMRT (Intensity Modulated Radiation Therapy), which is an irradiation method created three-dimensionally, or an X-ray source for CT.
[0024]
As described above, various modifications can be made to the embodiment described in detail within the scope of the present invention. By changing the density distribution of electrons generated by the high-energy electron source 2, the distribution of X-rays obtained can be changed. It is also possible to generate an electron beam that selectively uses a large number of through holes. Many through holes can be intentionally inclined.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a basic configuration of an X-ray generator according to the present invention.
FIG. 2 is a perspective view of an X-ray guide used in the X-ray generator according to the present invention.
FIG. 3 is a schematic diagram showing an X-ray generation state when a high-speed electron beam collides with a thin film target.
FIG. 4 is an enlarged cross-sectional view showing a part of an X-ray guide.
FIG. 5 is a schematic diagram showing the configuration of the first embodiment of the X-ray generator according to the present invention;
FIG. 6 is a schematic view showing a target plate and an X-ray guide wall used in the second embodiment of the X-ray generator according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vacuum container 2 High energy electron source 3 Target 4 X-ray guide 5 Electron capture electrode 7 Microwave source 9,10 High-speed electron beam 11, 12, 13, 14 X-ray 51 High-speed electron beam 52 First target plate 53 First X-ray guide Plate 54 Second target plate 55 Second X-ray guide plate 56 Third target plate 57 Third X-ray guide plate 58 Electrode 61 High-speed electron beam 62 Target 63 X-ray guide wall of tungsten 64 Central portion of X-ray guide formed of copper 65 66 67 68 69 X-ray 70 Fast electron beam transmitted through target

Claims (10)

A vacuum vessel;
An electron source disposed in the vessel for generating a fast electron beam;
An X-ray target disposed in the container and colliding with an electron beam from the electron source to generate X-rays on the back surface ;
It arranged a large number of uniform holes in the back of having the X-ray target, an X-ray guide for guiding the other surface by total reflection X-rays incident on the bore, and
An X-ray generation apparatus comprising an assembly similar to the assembly of the X-ray target and the X-ray guide, comprising an assembly of another X-ray target and an X-ray guide arranged in a column so that the holes correspond to each other . The X-ray generator according to claim 1, further comprising an absorption electrode that transmits X-rays that have passed through the X-ray guide and absorbs electrons . 2. The X-ray generator according to claim 1, wherein the target material is one or a combination of two or more metals selected from Au, W, Mo, Pt, and Re metal . 2. The X-ray generator according to claim 1 , wherein when the energy level of the electron beam is 1 to 10 Mev, the thickness of the target is 0.7 to 1.4 mm . 2. The X-ray generator according to claim 1, wherein when the energy level of the electron beam is 1 to 10 Mev, the inner diameter d of the hole of the honeycomb-shaped channel of the X-ray guide is 0.1 to 0.4 mm. An X-ray generator having a diameter D of 2 to 4 mm and an X-ray guide length L of 7 to 14 mm . 2. The X-ray generator according to claim 1 , wherein when the energy level of the electron beam is 10 Kev to 100 Kev, the thickness of the target is 0.07 to 0.14 mm . The X-ray generator according to claim 1, wherein the energy level of the electron beam is as low as 10 Kev to 100 Kev.
The inner diameter d of the hole of the honeycomb-shaped channel of the X-ray guide is 0.1 to 0.4 mm, the diameter D of the X-ray guide is 2 to 4 mm, and the length L of the X-ray guide is 0.7 to 1.4 mm. X-ray generator. 2. The X-ray generator according to claim 1 , wherein the material of the X-ray guide is Al, and a number of holes are manufactured by machining . The X-ray generator according to claim 1, wherein the X-ray guide is formed by binding a large number of metal pipes . A vacuum vessel;
An electron source disposed in the vessel for generating a fast electron beam;
An X-ray target disposed in the container and colliding with an electron beam from the electron source to generate X-rays on the back surface;
An input opening for receiving X-rays radiated from the back surfaces of the plurality of X-ray targets has a conical hole larger than an output opening, and the holes are disposed on the back surface of the X-ray target. An X-ray guide for guiding the X-rays incident on the hole to the other surface by total reflection; and
An X-ray generation apparatus comprising an assembly similar to the assembly of the X-ray target and the X-ray guide, comprising an assembly of another X-ray target and an X-ray guide arranged in a column so that the holes correspond to each other .

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