Patent Application
20130121462
This application claims, pursuant to 35 U.S.C. §119(a), priority to and the benefit of the earlier filing date of Korean Patent Application No. 10-2011-0119128, filed on Nov. 15, 2011, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to an X-ray generator emitting characteristic X-rays and an X-ray photographing apparatus including the X-ray generator.
2. Description of the Related Art
X-rays are used to perform non-destructive inspection, structural and physical property inspection of a material, image diagnosis, and security searching in the fields of industry, science, and medical treatment. In general, a photographing apparatus using X-rays includes an X-ray generator emitting the X-rays, and a detecting unit for detecting the X-rays that pass through an object.
Here, the X-ray generator generates the X-rays by generally generating electron beams emitted from an anode and colliding such electron beams with a cathode. The X-rays may be composed of Bremsstrahlung X-rays that are emitted mainly by deceleration of the electron beams, and characteristic X-rays emitted from an energy level of a target material.
The Bremsstrahlung X-rays represent a wide range spectrum, and thus may be referred to as polychromatic X-rays. Therefore, when the Bremsstrahlung X-rays are used, an X-ray image is produced, in which absorption coefficients of the material are mixed, and thus, contrast characteristics of the polychromatic X-ray image are degraded when the polychromatic X-ray image is compared with an image produced when the characteristic X-rays, which are monochromatic X-rays, are used. Thus, it is difficult to distinguish materials from each other in the target when using polychromatic X-ray imaging.
In addition, when the Bremsstrahlung X-rays are projected onto a human body, they are mostly absorbed by the human body, thus increasing the amount of radiation exposure to the human body. Therefore, a filter formed of aluminum or copper is generally disposed to remove the X-rays of a low level energy region and thus to prevent exposure of the human body to such low level energy X-rays, when imaging diagnosis is performed.
Therefore, research regarding the use of characteristic X-rays to obtain a high quality X-ray image or to perform the imaging diagnosis is being conducted, since there is a need to obtain such high quality X-ray images while minimizing exposure of a target, such as the human body, to the X-rays.
The present invention provides an X-ray generator that emits characteristic X-rays and an X-ray photographing apparatus including the X-ray generator.
According to an aspect of the present invention, there is provided an X-ray generator including: an electron beam emission unit that emits electron beams; an electron beam guide unit, in which the electron beam emission unit is disposed, for condensing the electron beams and making the electron beams proceed in a predetermined direction; and a target unit disposed to face the electron beam guide unit, and discharging X-rays when the electron beams collide with the target unit.
The target unit may be disposed perpendicularly to a proceeding direction of the electron beam.
The electron beam guide unit may include: an electron beam collecting unit, in which the electron beam emission unit is disposed, for collecting the electron beams emitted from the electron beam emission unit; an electron beam condensing unit for condensing the electron beams; and an electron beam incident unit for making the condensed electron beam incident into the target unit.
The electron beam collecting unit, the electron beam condensing unit, and the electron beam incident unit may be sequentially arranged from a side of the electron beam emission unit toward a side of the target unit.
At least one of the electron beam collecting unit, the electron beam condensing unit, and the electron beam incident unit may be separate and independent components.
A cross-sectional area of the electron beam collecting unit may be greater than a cross-sectional area of the electron beam incident unit.
A cross-sectional area of the electron beam condensing unit may be reduced gradually from a side of the electron beam collecting unit to a side of the electron beam incident unit.
The electron beam incident unit may be disposed to face the target unit.
Voltages applied to the electron beam collecting unit, the electron beam condensing unit, and the electron beam incident unit may be different from each other.
The voltage applied to the electron beam incident unit may be greater than the voltages applied to the electron beam collecting unit and the electron beam condensing unit.
The electron beam emission unit may be a filament forming an opening.
The target unit may be rotatable.
The target unit may discharge a plurality of characteristic X-rays having different spectrums from each other.
The plurality of characteristic X-rays may be sequentially discharged one by one.
The target unit may include a plurality of target areas that are formed of different atoms from each other, and may further include: a target holder supporting the target unit; and a target driving unit for moving the target holder so that the plurality of target areas may be selectively located in the proceeding direction of the electron beam.
The plurality of target areas may be arranged as a circle on the target holder, and the target driving unit may rotate or move the target holder in a pendulum motion.
According to another aspect of the present invention, there is provided an X-ray photographing apparatus including: an X-ray generator described above; and an X-ray detector for detecting the X-ray that is discharged from the X-ray generator to pass through an object.
The X-ray detector may be disposed on a same line as a proceeding direction of the electron beam that is incident into the target unit.
The electron beam emission unit may be disposed between the target unit and the X-ray detector.
The electron beam guide unit may include an opening.
The target unit may be disposed between the electron beam emission unit and the X-ray detector.
The X-ray detector may detect characteristic X-rays.
The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
Hereinafter, the present invention will be described in detail by explaining preferred embodiments of the invention with reference to the attached drawings. Like reference numerals in the drawings denote like elements. This invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. In the following description, a detailed explanation of known related functions and constructions may be omitted to avoid unnecessarily obscuring the subject matter of the present invention. Also, terms described herein, which are defined considering the functions of the present invention, may be implemented differently depending on user and operator's intention and practice. Therefore, the terms should be understood on the basis of the disclosure throughout the specification. The principles and features of this invention may be employed in varied and numerous embodiments without departing from the scope of the invention.
Furthermore, although the drawings represent exemplary embodiments of the invention, the drawings are not necessarily to scale and certain features may be exaggerated or omitted in order to more clearly illustrate and explain the present invention.
Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.
The electron beam emission unit 10 generates and emits the electron beams. The electron beam emission unit 10 may include a filament that is formed by using coils composed of, for example, tungsten. When an electric current flows through the filament, the filament is heated and the heated filament discharges the electron beams omni-directionally. Instead of or in addition to the filament, in alternative embodiments, the electron beam emission unit 10 may include a photocathode that may emit the electron beams, and/or an electron beam emission device of a field emission type. In addition, the electron beam emission unit 10 may include a carbon nano-generator. When the carbon nano-generator is used, the electron beams may be discharged at room temperature, and thus, a lifespan of the X-ray source is greatly increased. In addition, an efficiency of discharging the electron beams is superior when a carbon nano-generator is used, and thus, the X-rays may be emitted at a relatively high luminance and high efficiency. The electron beam emitted from the electron beam emission unit 10 is accelerated while traveling generally parallel to the x-axis toward the target unit 30, and thus, the velocity of the electron beam is sufficiently high to emit an X-ray when colliding with the target unit 30.
The electron beam guide unit 20 guides the electron beams emitted from the electron beam emission unit 10 so that the electron beams may be incident into a target area of the target unit 30. The target unit 30 is disposed and oriented perpendicularly to the direction of travel of a substantial number of the electron beams. Here, the perpendicular direction not only denotes an accurate right angle according to its mathematical meaning, but also includes a substantial right angle including errors that arise from installation and fabrication of the X-ray generator. That is, the target unit 30 has at least a surface oriented parallel to the y-z plane shown in
As shown in
In greater detail shown in
The electron beam condensing unit 24 condenses the electron beams emitted from the electron beam emission unit 10. The electron beam condensing unit 24 may be formed as a circular truncated cone with a conical axis parallel to the x-axis, and having an empty inner space so that electrons may proceed therein. In addition, one end of the electron beam condensing unit 24 faces the other end of the electron beam collecting unit 22, and the other end of the electron beam condensing unit 24 may face an end of the electron beam incident unit 26. In the exemplary embodiment, the electron beam condensing unit 24 tapers along the x-axis toward the electron beam incident unit 26 and the target unit 30, such that the cross-sectional area of the electron beam condensing unit 24 substantially parallel to the y-z plane may be reduced gradually from a side of the electron beam emission unit 22 toward a side of the target unit 30, with the cross-sections being oriented to be substantially parallel to the y-z plane and also parallel to the generally planar surface of the target unit 30, shown in
The electron beam incident unit 26 causes the condensed electron beams to be incident into the target unit 30. One end of the electron beam incident unit 26 faces the other end of the electron beam condensing unit 24, and the other end of the electron beam incident unit 26 may face the target unit 30. In particular, the electron beam incident unit 26 may be disposed in parallel to the target unit 30. That is, a cross-section of the electron beam incident unit 26 at its other end and the generally planar surface of the target unit 30 may be substantially parallel with each other, and in turn substantially parallel to the y-z plane, taking into consideration fabrication, implementation, and installation errors. When the other end of the electron beam incident unit 26 faces the target unit 30 in parallel with the generally planar surface of the target unit 30, shown in
Since the electron beam guide unit 20 not only prevents the electron beams from discharging outward along the x-axis direction away from the target unit 30, but also controls the direction of travel of the electron beams, the electron beam guide unit 20 may alternatively include an electronic lens. In addition, the electron beam guide unit 20 may be formed of an electrode or a coil. Thus, the electron beam guide unit 20 controls the movement of the electron beams by using an electric field or a magnetic field. In particular, when the electron beam guide unit 20 includes an electrode, voltages applied to the electron beam collecting unit 22, the electron beam condensing unit 24, and the electron beam incident unit 26 may be different from each other, with such voltages providing operating voltages to such units 22, 24, 26. For example, the voltages applied to the electron beam collecting unit 22, the electron beam condensing unit 24, and the electron beam incident unit 26 may be in an increasing numerical progression. As described above, when the voltages are applied to the electron beam guide unit 20, the electron beams are generated which may be incident into the target unit 30 at a high speed even when the electric current supplied to the electron beam emission unit 10 is not increased.
The electron beam guide unit 20 may include a conductive material such as a metal, a conductive polymer, or a conductive oxide material. For example, the electron beam guide unit 20 may be composed of Cu, Al, Au, Ag, Cr, Ni, Mo, Ti, Pt, or an alloy thereof, may be formed of thiophene or Poly(3,4-ethylenedioxythiophene) (PEDOT), and may be formed of TiO2 or IrOx.
In the exemplary embodiment of the present invention, as described herein, the electron beam collecting unit 22, the electron beam condensing unit 24, and the electron beam incident unit 26 of the electrode beam guide unit 20 are separate and independent components; however, the present invention is not limited thereto. For example, at least two of the electron beam collecting unit 22, the electron beam condensing unit 24, and the electron beam incident unit 26 may be integrally formed and/or fabricated together.
As described above, since the electron beam guide unit 20 condenses the electron beams emitted from the electron beam emission unit 10 and causes the electron beams to be incident into the target unit 30, a large amount of electron beams may be incident into the target unit 30 to generate a large amount of X-rays.
On the other hand, the target unit 30 discharges the X-rays when the electron beams collide with the target unit 30. The target unit 30 may be formed of a metal material such as copper, molybdenum, tungsten, or aluminum that may discharge the X-rays. The X-rays discharged from the target unit 30 may include at least one of a Bremsstrahlung X-ray and a characteristic X-ray. Here, the characteristic X-ray is discharged due to an energy difference when an electron included in an inner layer portion of an atom is discharged and then another electron enters into the inner layer portion, from where the first electron was discharged. Accordingly, the characteristic X-ray is composed of line spectrums of each atom's own line spectrum or a part thereof. Therefore, the target unit 30 may discharge an exclusive characteristic X-ray corresponding to the atoms according to the kind of atoms included in the composition of the target unit 30.
The X-ray generator 100 may further include a target driving unit (not shown) that drives or moves the target unit 30 so as to change a target area of the target unit 30. When the electron beams are incident into a certain region of the target unit 30, the target unit 30 may become heated, and thus, the operational lifespan of the X-ray generator 100 may be reduced. Therefore, the target driving unit moves the target unit 30, and thus moves the regions of incidence of the electron beams onto the target unit 30, so that the electron beams may be evenly incident into the surface of the target unit 30. For example, when the target unit 30 is formed as a disc shape, as described herein, the target driving unit may rotate the target unit 30, with the electron beam guide unit 20 being offset from the center of the disc shaped target unit to direct the incident electron beams into target areas of the target unit which are radially displaced from the center of the disc shaped target unit 30.
On the other hand, the target unit 30 may be formed of a substantially uniform composition of a metal material so that a particular kind of characteristic X-ray may be discharged. Otherwise, the target unit 30 may be formed of a plurality of metal materials or other known materials, so that a plurality of characteristic X-rays having different spectrums may be discharged to analyze an object precisely.
As shown in the exemplary embodiment of
Accordingly, the characteristic X-rays may be discharged selectively or sequentially. When the target driving unit rotates the target holder 40, the plurality of characteristic X-rays are sequentially discharged as each of the target areas 30a, 30b, 30c, 30d are exposed to the electron beams, and so characteristic X-rays are sequentially generated and discharged one by one. In an alternative embodiment, when the target driving unit moves the target holder 40 on an arm (not shown) by a certain angle (for example, by 90°) about a pivot point in a pendulum motion, only one characteristic X-ray is discharged. For example, the target holder 40 may be mounted on an arm, which swings about a pivot point to swing in a pendulum motion through the angle. The target holder 40 rotates or moves in the pendulum motion according to the kind or type of X-ray to be discharged.
The structure of the X-ray generator 100 is described as above. Hereinafter, an X-ray photographing apparatus 1000 including the X-ray generator 100 will be described.
The X-ray photographing apparatus 1000 includes the X-ray generator 100, an input unit 200, a control unit 300, an X-ray detector 400, an image data generator 500, a storage 600, and an output unit 700.
The X-ray generator 100 discharges X-rays to an object as described above. In the exemplary embodiment, the X-ray is discharged at appropriate times at an appropriate dosage in consideration of the radiation amount of the X-rays to be delivered to the object, such as a human subject, including a patient. Otherwise, different kinds of characteristic X-rays may be discharged according to the object.
The input unit 200 receives a command for an X-ray photographing operation from a user such as a medical expert. Information about a command for changing a location and direction of X-ray emissions of the X-ray generator 100, a command for discharging the X-ray, a command for adjusting a parameter in order to change the spectrum of the X-ray, a command for rotating the body of the X-ray photographing apparatus 1000 or the X-ray generator 100, and commands input from the user is transferred to the control unit 300. The control unit 300 controls the components in the X-ray photographing apparatus 1000 according to an input command of the user.
The X-ray detector 400 detects the X-ray that has passed through the object. The X-ray detector 400 may detect the characteristic X-ray. Whenever the X-ray generator 100 discharges the X-ray, the X-ray detector 400 detects the X-ray that has passed through the object and reached the X-ray detector 400. The X-ray detector 400 may be formed of a combination of a plurality of cells, each of which senses or otherwise detects the X-rays. In addition, the X-ray signal sensed by each of the cells is converted into an electric signal by the sensing cell. A flat panel detector may be used as the X-ray detector 400. The image data generator 500 receives the electric signal corresponding to the X-ray detected by the X-ray detector 400. The image data generator 500 generates digital data including information about a cross-section in the object from the received electric signal. The generated data is data about the cross-section in the object, and thus, is referred to as cross-section data. Once the X-ray is discharged, a single set of cross-section data including information about the cross-section of the object is generated. When the X-ray generator 100 discharges the X-rays a plurality of times while changing the position thereof, a plurality of sets of cross-section data, including information about different cross-sections of the object, is generated. When the plurality of cross-section data, including adjacent cross-sections, are accumulated, three-dimensional volume data showing the object three-dimensionally may be obtained.
The storage 600 includes at least one memory device and stores the cross-section data generated by the image data generator 500. In addition, the storage 600 also stores the three-dimensional volume data generated by the image data generator 500. The storage 600 transmits the stored cross-section data or the three-dimensional volume data to the output unit 700 according to a request of the user.
As described above, the X-rays discharged from the target unit 30 may include Bremsstrahlung X-rays and characteristic X-rays. The Bremsstrahlung X-rays and the characteristic X-rays may have different radiation types.
As shown in
As shown in
As described above, the X-ray detector 400 is disposed in a region or arranged, relative to the other X-ray components, where the characteristic X-ray may be detected easily without interference from the generated Bremsstrahlung X-rays, and thus, the X-ray photographing apparatus 1000 may not include or require a filter for removing the Bremsstrahlung X-rays, or may include a minimal filter for removing any Bremsstrahlung X-rays which may be directed toward the X-ray detector 400. In addition, since the data is analyzed by using the characteristic X-ray, an X-ray image having high clarity and high contrast may be obtained, since the negative effects of interference from the generated Bremsstrahlung X-rays on the imaging process is reduced and/or eliminated.
According to the X-ray generator of the present invention, a large amount of electron beams may be condensed and incident into the target unit 30, and thus, a large amount of characteristic X-rays may be generated.
In addition, since the X-ray detector 400 is disposed in parallel with the X-ray generator 100 along the x-axis in the incident direction; that is, the travel direction of the electron beams, the X-ray detector 400 may detect the characteristic X-rays easily, and unnecessary exposure of the object to the X-rays may be greatly reduced.
In addition, since the X-ray image is obtained by detecting the characteristic X-ray without interference from the generated Bremsstrahlung X-rays, the contrast of the image is high enough to distinguish the materials or to perform the diagnosis. Furthermore, by focusing the electron beams and the subsequent generation of characteristic X-rays while minimizing the radiation to the object from the generated Bremsstrahlung X-rays, the amount of exposure of the object, such as a human patient, to doses of X-rays is minimized, to improve the safety of the X-ray photographing process for the patients.
The above-described apparatus and methods according to the present invention can be implemented in hardware, firmware or as software or computer code that can be stored in a recording medium such as a CD ROM, a RAM, a floppy disk, a hard disk, or a magneto-optical disk or computer code downloaded over a network originally stored on a remote recording medium or a non-transitory machine readable medium and to be stored on a local recording medium, so that the methods described herein can be rendered in such software that is stored on the recording medium using a general purpose computer, or a special processor or in programmable or dedicated hardware, such as an ASIC or FPGA. As would be understood in the art, the computer, the processor, microprocessor controller or the programmable hardware include memory components, e.g., RAM, ROM, Flash, etc. that may store or receive software or computer code that when accessed and executed by the computer, processor or hardware implement the processing methods described herein. In addition, it would be recognized that when a general purpose computer accesses code for implementing the processing shown herein, the execution of the code transforms the general purpose computer into a special purpose computer for executing the processing shown herein.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2011-0119128 | Nov 2011 | KR | national |
