Patent Application
20110087062
This application claims priority of German application No. 10 2009 049 182.1 filed Oct. 13, 2009, which is incorporated by reference herein in its entirety.
The invention relates to a miniature X-ray tube and a catheter with a miniature X-ray tube.
Conventional X-ray tubes substantially comprise a vacuum chamber with a housing enclosing a cathode and an anode. The cathode forms the negative electrode, which emits electrons toward the positive anode. The electrons are attracted from the anode and strongly accelerated by an electrical field between the anode and cathode. The anode is typically made of a metal, for example tungsten, molybdenum or palladium. When the electrons bombard the anode, their energy is for the most part converted into heat. Only a fraction of the kinetic energy can be converted into X-ray photons, which are emitted by the anode in the form of an X-ray beam. The X-ray beam generated in this way exits the vacuum chamber through a radiation-permeable window made of a material with a low atomic number.
Applications in industrial and medical imaging and for therapeutic treatment are nowadays unimaginable without X-ray devices. X-ray devices are also used to treat vascular diseases inside patients' bodies. For this, X-ray devices must be miniaturized sufficiently to enable them to be introduced into a patient's vessels.
An X-ray tube of this kind is disclosed in DE 198 29 444 A1. The X-ray device is preferably arranged at the distal end of a catheter. The X-ray tube has a vacuum housing equipped with a cylindrical housing section the inside wall of which is coated with a target material. A cylindrical isocentrically arranged field emission cathode extending along the longitudinal axis is located in the vacuum housing and emits electrons radially outward in the direction of the target material for the generation of X-rays. When the electrons hit the target material, X-rays are generated which penetrate the vacuum housing. The X-ray tube can be designed small enough to enable the treatment of even coronary vessels.
For some time now, carbon nanotubes have also been used to build cathodes for multi-beam X-ray tubes. For example, PCT application WO 2004/110111 A2 discloses an X-ray tube of this kind. The multi-beam X-ray tube comprises a stationary field emission cathode and an anode facing the cathode. The cathode comprises a plurality of stationary, individually controllable electron-emitting carbon nanotubes disposed in a predetermined pattern on the cathode. The anode comprises a plurality of focal points disposed in a predetermined pattern corresponding to the pattern of the carbon nanotubes. A vacuum chamber encloses the anode and cathode.
The solution disclosed in WO 2004/110111 A2 offers many advantages compared to conventional thermionic sources of X-radiation. It eliminates the anode's heating element, operates at room temperature, generates pulsed X-rays with a high repetition rate and generates a plurality of beams with different focal points.
The object of the invention is to utilize the advantages of cathodes with carbon nanotubes with miniaturized X-ray devices and to disclose an improved miniature X-ray device for a catheter.
According to the invention, the object is achieved with the miniature X-ray tube and the catheter described in the claims.
The invention claims a miniature X-ray tube for intravascular or intracorporeal radiation treatment in living beings with a housing comprising a cylindrical housing section with a longitudinal axis. The miniature X-ray tube also comprises a cylindrical or cylindrical-tube-shaped first field emission cathode arranged concentrically about the longitudinal axis in the housing section with a plurality of carbon nanotubes, which emit electrons radially outward, and/or in the housing section a second field emission cathode with a plurality of carbon nanotubes, which emit electrons in the direction of the longitudinal axis. The invention has the advantages that the miniature X-ray tube only emits little heat and is robust against mechanical stresses. In addition, the design is simpler than those known from the prior art. It is also advantageous that it is possible to establish an optimum distance between the first field emission cathode and the housing section (outer sleeve).
In a further embodiment, the carbon nanotubes can be arranged on the internal or external side of the cylindrical-tube-shaped first field emission cathode or on the external side of the cylindrical first field emission cathode. This permits a homogeneous dose distribution of the X-rays.
In a development, a plurality of cylinder rings to which are applied carbon nanotubes form the field emission cathode.
Advantageously, a flexible film can be applied to the carbon nanotubes to form the first field emission cathode.
In addition, the carbon nanotubes can be printed or sputtered onto the flexible film.
In a preferred embodiment, the miniature X-ray tube can comprise at least one tubular-cylinder-shaped anode arranged outside the first field emission cathode concentrically to the longitudinal axis in the housing section.
The invention also claims a catheter with shaft, the distal end of which is provided with a miniature X-ray tube according to the invention. The advantage of this is that it is possible to produce a compact and inexpensive tool for intravascular and intracorporeal radiation treatment of living beings.
Further special features and advantages of the invention are evident from the following explanation of several exemplary embodiments with reference to schematic drawings, which show:
The carbon nanotubes can, for example, be applied by laser-coating onto the external side of a cylindrical tube serving as a carrier.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2009 049 182.1 | Oct 2009 | DE | national |
