EP3685420A1

EP3685420A1 - Mbfex tube

Info

Publication number: EP3685420A1
Application number: EP18779196.7A
Authority: EP
Inventors: Johannes Ringel; Bo Gao; Houman Jafari
Original assignee: Cetteen GmbH
Current assignee: Cetteen GmbH
Priority date: 2017-09-20
Filing date: 2018-09-20
Publication date: 2020-07-29
Anticipated expiration: 2038-09-20
Also published as: CN111448637B; ES2957611T3; JP2020533767A; US20200312601A1; JP7015383B2; EP3685420B1; CN111448637A; DE102017008810A1; EP3685420C0; US11183357B2; WO2019057338A1

Abstract

The invention relates to a MBFEX tube (1) for an x-ray device, comprising, in a vacuum tube (20), an anode (30) designed as a coolant finger and securely fixed in the tube, also comprising a plurality of securely arranged cathodes (40, 41, 42). The vacuum tube (20) comprises a plurality of cathode feed lines (50) and not more than two high-voltage bushings (51, 52), in a high voltage bushing (52). A coolant pipe (31) comprising an coolant inner tube (32) mounted inside in a bushing. The coolant tube (31) and the coolant inner tube (32) are provided for cooling the anode (30) with a liquid coolant, the cathodes (40, 41, 42) being provided for field emission of electrons and being respectively arranged on the anode (30) for generating x-ray sources (Q).

Description

MBFEX tube

The invention relates to an M BFEX tube (MBFEX = Multibeam Field Emission X-Ray) for an X-ray apparatus, which is also referred to as a multi-focus field emission X-ray tube.

Such X-ray tubes are known, for example, from the paper: Yang Lu, Hengyong Yu, Guohua Cao, Jun Zhao, Ge Wang, Otto Zhou, Medical Physics 2010, Volume 37, pp. 3773-3781 and US Pat. No. 7,751,528 B2, the cathodes Carbon nanotubes for

Field emission of electrons included. The MBFEX tubes described therein are intended for use in computer tomographs in which instead of a rotation of an X-ray emitter sequential electrical circuits of individual fixed X-ray emitter are made.

In connection with electron emitters which contain nanorods, in particular carbon nanotubes, reference is also made by way of example to the documents WO 2018/086737 Al and WO 2018/086744 A2.

Various M BFEX tubes, which are described in US Pat. No. 7,751,528 B2, have fixed X-ray emitters, in each of which a cathode is assigned to an anode. Thus, a total of a plurality of cathodes and a corresponding plurality of anodes are present. While the anodes are set to high DC potential, the cathodes are individually to control.

The invention has for its object to provide a manufacturing technology in comparison to the prior art easily realizable and structurally compact MBFEX tube available. This object is achieved by the proposed MBFEX tube with the features of claim 1. Further, the object is achieved by an arrangement of several MBFEX tubes according to claim 27. The MBFEX tube can be produced according to claim 28 and operated according to claim 30.

The proposed MBFEX tube is provided for an X-ray machine and has in a vacuum tube a fixedly arranged therein and designed as a cold finger anode and a plurality of rows arranged fixed cathodes. The vacuum tube again has a plurality of cathode leads and not more than two

High voltage bushings on. Here, in a high-voltage bushing, a coolant pipe is arranged, in which a further pipe, that is to say coolant inner pipe, is arranged. Here, either the outer or the inner tube can act as a coolant supply pipe, wherein the respective other tube is provided as a coolant discharge pipe.

The coolant supply pipe and the coolant discharge pipe are provided for cooling the anode with a liquid coolant. The cathodes are provided for the field emission of electrons and in each case aligned with respect to their electron main emission direction to the common anode for generating X-ray sources. The X-ray sources on the anode emit X-ray beams each having an X-ray main emission direction. The x-ray sources are preferably arranged in rows on the anode.

The invention is based on the first inventive concept, to solve the

Cooling problem of the anode, which is given in MBFEX tubes according to the prior art, to form the anode of the proposed MBFEX tube itself as a cooling device in the form of a cold finger. In this sense, in the proposed MBFEX tube, the anode is hollow, with the cavity being clamshell shaped to accommodate both the

Supply as well as the discharge of coolant to allow. For example, it is at the inner tube around the coolant supply tube and at the outer tube concentrically surrounding the inner tube around the coolant discharge tube.

The anode including the coolant tubes is closed at one end. At this end of the elongate anode, the transition between the coolant supply pipe and the coolant discharge pipe is formed. Low-viscosity silicone oils, in particular having a boiling point of more than 450 ° C., are suitable as liquid coolants, inter alia. Also

Insulating oils marketed under the trademark "Shell Diala" can be used as a coolant to cool the anode.

The design of the anode as a cold finger not only corresponds to a particular

advantageous compact design, but has the advantage that both the

Coolant discharge pipe and the coolant supply pipe at one of the two ends of the anode by a passage through the vacuum tube with a coolant circulating device is connectable.

The anode contains, for example, molybdenum and / or tungsten and optionally has a coating suitable for the emission of X-rays on the outer surface. According to an advantageous development are compared to the elongated basic shape inclined surface sections of the anode formed by attachments of the anode.

In this case, the individual articles have different skew angles relative to the elongated base body of the anode. In this way, it is possible with a particularly high degree of efficiency to align the x-ray radiation produced at the individual attachments by incident electrons in the direction of the isocenter of the x-ray system comprising the MBFEX tube. This result can also be achieved by making said surface sections by grinding in the anode. A coating of the anode can be located either on its entire surface or only on portions of the surface, namely on the attachments or in the grinding. The anode of the x-ray tube is preferably designed as a non-rotating anode. In principle, a rotation of the anode about its own axis can also be provided for the purpose of further improved cooling.

The production of small feedthroughs by means of a vacuum tube for X-ray machines is easy to manufacture with regard to sealing against the outside atmosphere. The cathode leads of the proposed MBFEX tube are provided as terminals of the cathodes to an electrical voltage, typically in the amount of less kV, in particular up to 4 kV, and are formed for example as wire leads. If, for example, the vacuum tube is made of glass, then cathode leads in the form of wires can be easily fused into the vacuum tube, such feedthroughs having a high and long-lasting seal.

Larger bushings, for example for high-voltage electrical connections or for pipes, in a vacuum tube, however, must be laboriously sealed. Therefore, it is advantageous to have a larger number of such larger feedthroughs on one

To avoid vacuum tube. In terms of a second inventive concept, this is achieved in the proposed MBFEX tube in that the coolant discharge tube is passed together with the coolant supply tube through a high-voltage feedthrough. The high voltage bushings are designed to connect the anode to a high voltage electrical system. The connection of the anode to a

High voltage is preferably at each end of this.

Between the cathodes and the anode focusing electrodes are fixed in the

Vacuum tube arranged, which can be connected for example via electrical leads in the cathode leads to an electrical voltage. The

Focusing electrodes are located in the space between extraction grids that are slightly spaced from the cathodes and the anode.

Structures of the extraction grids can be produced particularly precisely by laser processing. In particular, a picosecond or femtosecond laser for structuring the Extraction grid suitable. The precise production of the extraction grid is an essential prerequisite for the fact that electronically emitted from the cathode with a high degree of transmission reach the anode. During operation of the MBFEX tube, among other things, the electron source including the extraction grid is exposed to thermal stresses. To allow deformation of the extraction grid by these loads

minimize, preferably a special design of the extraction grid is realized:

The extraction grid basically has one of the shape of the associated electron source, that is, cathode, adapted basic shape, in particular a rectangular basic shape. The long sides of this rectangle are formed by so-called edge strips of the extraction grid. The two edge strips are integrally connected to each other by transverse to these grid strips. For the absorption of thermally induced deformations, the transition areas between the grid strip and the edge strips are of particular importance. Particularly advantageous is a curved transition between the grid strip and edge strips has been found. In this case, the curvatures at the two ends of the grid strip are preferably aligned in opposite directions. For example, if, in plan view of the extraction grid, one end of the lattice strip curved upward at its transition to the edge strip, the other end of the lattice strip at the transition to the opposite edge strip is curved downwards. The grating strips thus each have an elongated S-shape, wherein the distance between the individual grating strips over the entire length thereof is at least approximately constant. Each grid strip in this case connects at a non-right angle to the edge strip. Instead of an elongated S-shape of the grid strip this can also have another suitable shape for a length compensation. For example, in each grid strip, in particular near the

Transition regions to the edge strips, arcuate, for example, semicircular, curved sections to be integrated. It is also possible to make sections of the grid strip with simple or Z-shaped angled portions, preferably in a rounded shape. In all cases, the spacing between adjacent grid strips is preferably constant over the entire length of the grid strips. The distance between each point of the extraction grid and the electron emitter is not only in the cold state of the MB FEX tube, but at any point in time

Proper operation with a very good approximation constant. Also

Extraction gratings are also components of the focusing device precisely machinable with pulsed laser radiation. The extraction grid can as well as

Focusing components, for example, made of steel, especially stainless steel.

The x-ray beams that can be generated at the x-ray sources on the anode each have a direction with the maximum intensity of the emitted x-ray radiation, which corresponds to the respective x-ray main emission direction. Such an X-ray main emission direction is given in all X-ray sources, which of a

Shot blasting source are different. The X-ray beam geometry detected by the X-ray detector also depends on the collimation of the X-ray radiation, apart from the focusing of the electron beam. Here, an X-ray window in the

Vacuum tube formed as a collimator device and / or attached to a collimator device in front of an X-ray window on the vacuum tube.

Fan-shaped x-ray beams (fan beam) and / or cone-shaped x-ray beams (cone beam) can be generated with the MBFEX tube, for example. Each of the x-ray sources formed on the anode may, for example, be approximately punctiform, flat or line-shaped. The cross-sectional profile of the X-ray radiation in the isocenter of the X-ray system, in particular the tomography system, depends, apart from the shape of the X-ray source, above all on the collimation of the X-radiation.

In the proposed MBFEX tube, the cathodes are preferably arranged in a row in such a manner that, in cooperation with the focusing electrodes on the anode, a likewise row-shaped arrangement of X-ray sources is produced. The cathodes are intended for sequential electrical control. In one

Computed tomography is the proposed MBFEX tube instead of a rotating X-ray source used. Below will be discussed on individual advantageous developments of the proposed MBFEX tube.

In a preferred embodiment of the MBFEX tube, the high voltage feedthroughs and the cathode leads are arranged in a row and the anode opposite one another on the vacuum tube. This means that viewed in cross-section of the MBFEX tube, the cathode leads and high-voltage feedthroughs on the one hand and the anode on the other hand are diametrically opposed. With such an arrangement, the high voltage feedthroughs and the cathode leads are exposed to only a minimum of secondary electron or ion radiation. Particularly advantageously, such an arrangement also allows easy installation of the proposed MBFEX tube in an X-ray machine, for example in the gantry of a computer tomograph.

In a preferred embodiment of the proposed MBFEX tube, their cathodes have carbon nanotubes. The very high electrical and thermal conductivity of carbon nanotubes allows a high current carrying capacity without significant heat development on the individual carbon nanotubes themselves. Carbon nanotubes have a low field strength threshold of less than 2 V / m for the

Field emission of electrons. The field strength threshold for cathodes for emitting electrons comprising carbon nanotubes can be further reduced by arranging the carbon nanotubes in a perpendicularly preferred direction on the cathode surface. Since single-walled carbon nanotubes are semiconductors and multi-walled carbon nanotubes metallic conductors, are multi-walled

Carbon nanotubes are particularly suitable for use as electron emitters on the cathodes of the proposed MBFEX tube. Therefore, the operation of the proposed MBFEX tube, which has cathodes containing carbon nanotubes, can be accomplished particularly advantageously with a power supply of relatively low power. In addition to carbon nanotubes, nanorods of a different kind, commonly referred to as nanosticks, are also suitable for the emission of electrons within the MBFEX tube. In a preferred embodiment, field emission cathodes are formed from such nanosticks as cathodes of the x-ray tube.

The nanosticks of the cathode are preferably made of a material which is as low as possible in terms of the quantum-mechanical field emission effect

Electron work for field emission of electrons. In this case, the nanosticks have a uniform or non-uniform composition and are either in the form of hollow bodies, ie tubes, or solid. The cathodes can have nanosticks of the same kind or a mixture of different types of nanosticks, whereby the type of nanosticks is based on their composition and composition

Material modification relates.

Suitable materials in pure or doped form for the field emission of electrons are, in addition to single or multiwalled carbon nanotubes, also single or multiwalled hetero-nitrogen carbon nanotubes, borides of rare earths, in particular

Lanthanum hexaboride and cerium hexaboride, metal oxides, in particular TiO ₂ , MnO, ZnO and Al ₂ O ₃ , metal sulfides, in particular molybdenum sulfide, nitrides, in particular boron nitride,

Aluminum nitride, carbon nitride, gallium nitride, carbides, especially silicon carbide, silicon. As starting materials for producing the nanoticks, which emit electrons during operation of the cathodes, rod-shaped, optionally hollow, elements made of polymeric materials are also suitable. The nanosticks of the cathodes are optional

Starting products, which only partially, in particular in the form of a coating, polymer materials manufactured.

In a particularly preferred embodiment, the cathodes on the surface nanosticks in a vertical direction, that is, in the direction of the anode, on. When operating the X-ray emitter and with sufficient distance between them are on the At the tips of the nanoticks very strong electric fields can be generated, whereby the emission of electrons is considerably simplified.

In a possible embodiment of the proposed MBFEX tube is in the

Vacuum tube arranged more than one type of cathode, wherein the term "variety" can refer both to the geometry and other properties of the cathode, for example, on the materials.Cathodes of the same and different types are fundamentally in any way electrically driven sequentially. In addition to the cathodes themselves, there may also be differences in focusing, which together with properties such as the surface geometry of the individual cathodes

different electron beams and ultimately different

X-ray beam generated.

The nanorods of the cathode have, for example, a length of less than 20 μm and a diameter of less than 10 nm, whereby a density of at least 10 ⁶ nanorods per cm ² , based on the area of the cathode, is given.

A screen printing process is suitable for producing the nanorod-containing cathode. Thus, in comparison to conventional methods, in particular for the method of electrophoretic deposition (EPD), a particularly uniform layer thickness and a relatively smooth surface of the emitter can be achieved. Preferably, at least one type of cathode forms a layer formed for emission of electrons having a thickness of less than 20 μm and a mean roughness (Ra) of less than 2.5 μm. The high quality of the emitter layer, together with a constant distance to the extraction grid, contributes to a high transmission rate of the X-ray tube electron source of up to 90% and more. The high transmission rate is also favored by the main orientation of the nanorods in the vertical direction, effected by the screen printing method, relative to the substrate surface on which the emitter layer is located. It is also possible within the same MBFEX tube both cathodes with carbon nanotubes as well as completely different cathodes, for example, cathodes with tips of tungsten, which work in other, basically known way to

use. Likewise, dispenser cathodes can be used within the MBFEX tube. In this context, reference is made to the documents DE 10 2011 076 912 B4 and DE 10 2010 043 561 AI.

As far as the cathodes are designed as field emission cathodes, the complete emitter arrangement preferably has the following layer structure:

As the lowermost layer of the emitter arrangement, a planar carrier element, in particular in the form of a ceramic plate, is provided. The ceramic board is made of corundum, for example. The emitter layer is located on the ceramic board. In areas next to the flat emitters, the ceramic plate is covered by a metal intermediate plate, which is also referred to as a spacer. On the intermediate metal plate, which is placed on a defined electrical potential, there is a so-called grid plate including the extraction grids assigned to the individual emitters. The grid plate in turn is covered by a plate of electrically insulating material, in particular ceramic, which generally referred to as the upper insulating layer. The term "upper" layer has no relation to the orientation of the electron emitter in space, but simply means that said layer is located closest to the anode of the x-ray tube.

In a particularly preferred development of the proposed MBFEX tube, the anode encloses an intended examination area at least partially. In this case, the X-ray sources and the main X-ray emission directions also at least partially surround the examination area. The examination area is provided for the positioning of an examination subject in an X-ray machine. For example, the MBFEX tube as a whole is curved, with which it already partially encloses the examination area as a single X-ray tube. A further

Enclosing the examination area can be realized in different ways:

For example, the MBFEX tube can extend over a very large angle, in extreme cases up to approximately 360 °, that is to say have an approximately closed ring shape. Alternatively, it is possible to assemble a ring mold from individual MBFEX tubes. The individual MBFEX tubes can either be curved or straight. In the latter case, a polygon shape of the arrangement results from all MBFEX tubes. Also incomplete polygon shapes or ring shapes, such as L-shapes, U-shapes or semicircles, can be produced by combining several MBFEX tubes, whereby not necessarily all MBFEX tubes of such arrangements are similarly shaped.

By an arcuate concave arranged around the examination area anode of the MBFEX tube is in a computed tomography compared to

conventional designs, the focus blur reducible and achievable a higher and constant image resolution, especially when the anode is formed as a circular arc. If the anode is designed as a circular arc, then all X-rays are equally aligned with an examination subject. Among other things by the

Minimizing the number of high-voltage bushings, the object to be examined can be transilluminated practically from all circumferential positions by means of a single MBFEX tube.

The proposed MBFEX tube is characterized by a compact and robust manufacturing technology that is particularly easy to implement compared with the state of the art

Construction and is particularly suitable for computer tomography to replace a rotating X-ray source. The vacuum tube in which the X-radiation is generated is preferably made of metal.

With the help of cathodes of different types, which are arranged in one and the same MBFEX tube, are easily different radiographs, which are different from each other in terms of dose, can be generated. This provides a simple possibility of dose modulation. The number of MBFEX tubes in an X-ray system is fundamentally not limited, as is the shape of the individual MBFEX tubes and the geometrical arrangement of the MBFEX tubes in relation to each other. Similarly, the MBFEX tube or a plurality of MBFEX tubes within a X-ray system can be combined with other types of X-ray tubes. In general, X-rays of different wavelengths, as provided for multi-energy or dual-energy recordings, can be generated by various settings of the anode voltage.

Irrespective of the design of the cathodes, successive X-ray pulses of different wavelengths can be generated by the MBFEX tube in a preferred process control. This is particularly high reliability and at the same time shorter

Recording time different materials within the study volume distinguishable from each other.

In the sense of a low susceptibility to interference and avoidance of damage, at least minimizing damage, in the case of possible disturbances, it has proven to be particularly advantageous to ground various components of the MBFEX tube to be zeroed in different ways. This applies in detail

Focusing electrodes as well as the electron emitters, which contain carbon nanotubes or other nanoticks, immediately preceding extraction grid:

While passive focusing electrodes are grounded in a preferred embodiment of a housing, the grounding of the extraction grid is independent of said housing, for example via a separate grounding line, which may be associated with a unit for driving the electron emitter.

The advantage of the separate grounding of focusing electrodes and extraction grating comes into play if, due to a flashover, the potential of the focusing electrodes - despite grounding - due to the very high potential on which the anode is briefly raised. If, at this moment, the extraction grid together with the focusing electrodes were grounded, this would result in a correspondingly increased potential of the extraction grid and thus an increased voltage difference between the carbon nanotubes and the extraction grid. Due to the given, pronounced voltage dependence of the electron emission of the

As a result, carbon nanotubes would extremely increase the electron emission, which would entail the risk of damaging the X-ray tube. Such

Danger of damage is avoided by the separate grounding of focusing electrodes on the one hand and extraction grille on the other hand.

The proposed MBFEX tube will be explained in more detail below with reference to a drawing, in which various exemplary embodiments are summarized. Herein show, in a partly roughly simplified representation:

Fig. 1 shows a first embodiment of a MBFEX tube 1 in a schematic

Top view of an arc formed as an anode 30,

Fig. 2 shows the first embodiment of a MBFEX tube 1 in a schematic

Side View,

3 shows a second embodiment of a MBFEX tube 1 with a straight, line-shaped anode 30,

Fig. 4 shows the second embodiment of a MBFEX tube 1 with cut

View of the anode 30,

5 shows a high-voltage feedthrough 52 of the MBFEX tube 1 according to FIG. 3, FIG. 6, 7 are partial views of a grating device 43 of the MBFEX tube 1 of the first embodiment of a computer tomograph,

Fig. 8, 9 are partial views of the grating device 43 of the MBFEX tube 1 of the second

Embodiment of a computer tomograph,

10, 11 are partial views of an alternative embodiment of a grating device 43

a MBFEX tube 1,

12 shows an emitter arrangement 33 of an MBFEX tube 1 in an exploded view,

13 shows an upper insulating layer 48 of the emitter arrangement 44 according to FIG. 12,

14 is a grid plate 47 of the emitter assembly 44 of FIG. 12,

FIG. 15 shows an extraction grid electrode 71 of the grid plate 47 according to FIG. 14, FIG.

FIG. 16 shows a metal intermediate plate 46 of the emitter arrangement 44 according to FIG. 12, FIG.

Fig. 17, 18 the front of a ceramic board 45 of the emitter assembly 44 after

Fig. 12,

19 shows the back of the ceramic plate 45 of the emitter assembly 44 of FIG. 12, 20 is a detail of the ceramic board 45,

a detail of a MBFEX tube 1 with two different types of cathodes 41, 42,

22, 23 an example of an overall annular arrangement of several MBFEX tubes 1 in two different views,

24, 25 an example of a total polygonal arrangement of several MBFEX tubes 1 in two views analogous to FIGS. 22 and 23,

26, 27 a plurality, each acting as an X-ray source essays 33 having

Anode 30 of a MBFEX tube 1,

in three-dimensional representation, the shape of a cathode 40 of a MBFEX tube 1 and for comparison, a conventional cathode form,

in a diagram current and voltage pulses during operation of the MBFEX tube 1.

All embodiments of the proposed MBFEX tube 1 explained below are provided for a computer tomograph and have a vacuum tube 20 with an X-ray window 21. In the vacuum tube 20 of all embodiments, designed as a cold finger anode 30 is fixed. The anode 30 contains tungsten. The first two embodiments of the proposed MBFEX tube have in the vacuum tube 20 a plurality of uniformly arranged in rows fixed cathodes 40 and the embodiment of FIG. 21 such cathodes 41, 42 of two different types, wherein the cathodes 40, 41, 42 for the field emission of

Electrons are provided. The cathodes 40, 41, 42 are respectively aligned with the electron main emission direction e of the producible electron beam E on the common anode 30 for generating X-ray sources Q. The cathodes 40, 41, 42 are fixedly arranged in a row in such a way that a likewise row-shaped arrangement of X-ray sources Q can be produced on the anode 30. The cathodes 40, 41, 42 are provided for a sequential electrical drive. The X-ray beams X each have an X-ray main emission direction x.

In all embodiments, each grating device 43 is aligned with each X-ray source Q. The grating devices 43 are fixedly disposed in the vacuum tube 20 between the cathodes 40, 41, 42 and the anode 30. Each grating device 43 has an extraction grid. The extraction gratings are arranged at a short distance in front of the cathodes 40, 41, 42 and are provided for the extraction of electrons in the form of an electron beam E from the cathodes 40, 41, 42. The extraction grids are not shown in FIGS. 1 to 4.

The vacuum tube 20 of all embodiments in turn has a plurality of

Cathode leads 50 and two high-voltage bushings 51, 52 on. The

Cathode leads 50 are provided as terminals of the cathodes and the grating devices 43 to an electrical voltage of a few kV and formed as wire leads. The high-voltage bushings 51, 52 are provided for the respective end-side connection of the anode to a high electrical voltage of several 10 kV. Typically, the high voltage is in the range of 10 kV to 420 kV. Values in the upper range of this interval are used, for example, in X-ray systems

Investigation of larger items selected in the non-medical field. In a high voltage bushing 52, a coolant discharge pipe 31 is passed with an internal coolant supply pipe 32. The coolant discharge pipe 31 and the coolant supply pipe 32 are provided for cooling the anode 30 with a liquid, electrically non-conductive coolant by means of a circulating device.

In all embodiments of the proposed MBFEX tube 1 are characterized by the

Cathodes 40, 41, 42 in cooperation with the anode 30 x-ray pulses of uniform or alternating alternating energy generated. By way of example, FIG. 29 shows the time profile of an emitter current EC, an anode current AC, and the grating-emitter voltage GEV. The diagram of FIG. 29 shows actual measurement data. Of particular note is the high transmittance of about 90%, which indicates the ratio of anode current AC to emitter current EC. In the present case, the anode current AC 52.2 mA determined from the measured voltage values and the emitter current EC 58.2 mA. This extremely favorable ratio between anode current AC and emitter current EC results primarily from the high quality of the hereinafter described in more detail

Emitter array 44 of the X-ray tube 1.

The first embodiment of the proposed MBFEX tube 1 will be explained in more detail with reference to FIG. 1 and FIG. 2. In the first embodiment, the anode 30 is formed as a circular arc.

Fig. 1 shows a schematic plan view of the anode 30, wherein the vacuum tube 20, the grating devices 43 and the high-voltage bushings 51, 52 are not visible. Fig. 1 is not to scale. The anode 30, the cathodes 40 and the

Grating devices 43 are disposed within the vacuum tube 20. In this case, the cathodes 40 are located on a carrier 6 made of metallized ceramic. The anode 30 is fixed in the vacuum tube 20 independently of the cathodes 40. The X-ray sources Q are arranged so that the generated X-ray beams X in their respective

X-ray main emission directions x are aligned on an examination area U. The examination area U is provided for the positioning of an examination subject, in particular a patient.

Fig. 2 shows the proposed MBFEX tube 1 in its first embodiment in a side view in cross section. In Fig. 2, the coolant supply pipe 32, the cathode leads 50 and the high voltage bushings 51, 52 are not visible. The cathodes 40 have on their surface multi-walled carbon nanotubes in a vertical preferred direction. By "perpendicular" in this context is meant to be directed to the anode 30 orientation.

The second embodiment of the proposed MBFEX tube 1 will be explained in more detail with reference to FIG. 3 and FIG. 4. The second embodiment

differs from the first embodiment only in that the anode 30 is formed linear.

Fig. 3 shows a partially sectional view of the MBFEX tube 1 of the second embodiment. In Fig. 3, the coolant supply pipe 32, the cathodes 40 and the grating devices 43 are not visible. As in the first embodiment of the MBFEX tube 1, cathode leads 50 and the high voltage feedthroughs 51, 52 are arranged in a row and the anode 30 is disposed opposite to the vacuum tube 20.

FIG. 4 shows the proposed MBFEX tube 1 in its second exemplary embodiment with a sectional view of the anode 30. In FIG. 3, the cathodes 40 and the grating devices 43 are likewise not visible. Individual features of the high voltage bushing 52 will be apparent from FIG.

An existing in all embodiments grating device 43, which is shown in detail in different variants in Figures 5 to 11, is aligned with the anode 6, that is, between the cathodes 40, 41, 42 and the anode 6 in the

Vacuum tube 20 is arranged. The grating device 43 includes by definition at least one extraction grid electrode 71, 73, 74 and at least one form of focus electrodes 72, 75, 76.

The extraction grid electrodes 71, 73, 74 are fixedly disposed directly over the cathodes 40, 41, 42 and provided for field extraction of electrons from the cathodes 40, 41, 42. The focusing electrodes 72, 75, 76 are also fixedly disposed directly over each extraction grid electrode 71, 73, 74, facing the anode 6 and provided for focusing the extracted electrons as an electron beam E onto the respective X-ray source Q to be generated. The extraction grid electrodes 71, 73, 74 are grounded independently of focusing electrodes 72, 75, 76. The focusing electrodes 72, 75, 76 may be operated as passive or active focusing electrodes.

In the first exemplary embodiment, the grating device 43 has an extraction grid electrode 71 which is common to all the cathodes 40, wherein each individual cathode 40 is assigned separately to a single focusing electrode 72. In the second embodiment, the grating device 43 has a cathode 41 of the first kind common

Extraction grid electrode 73 of a first form and a second form of the cathodes 42 of the second type extraction grid electrode 74, each of each individual cathode 41 of the first kind separately a single focusing electrode 75 of a first form and each individual cathode 42 of the second kind separately a single Focusing electrode 76 is associated with a second mold. The extraction grid electrodes 71, 73, 74 and the focusing electrodes 72, 75, 76 are not shown in FIGS. 1 to 4.

For a computer-assisted x-ray imaging by means of tomosynthesis, a time-constant potential of typically 40 kV is applied to anode 6, with a uniformly pulsed direct electrical current of 30 mA flowing between anode 6 and respectively connected cathode 40, 41. For computer-assisted X-ray imaging using HPEC Tomosynthesis, however, is on the anode in question a time-constant potential of typically 120 kV, between the anode 6 and the respective connected cathode 40, 42 flows a uniformly pulsed DC electrical current in the order of 0.5 mA.

In all embodiments, the proposed computed tomography system includes a current controller, a device controller, an electronic control system (ECS), a cathode high voltage (CPS) source, an anode power supply (APS), and a device controller on. The current controller, the device controller, the electronic control system, the cathode high voltage source, the anode high voltage source and the device control are part of an electronic control device. The current controller, the device controller and the electronic control system constitute an electronic control system.

The electronic control device has a main electrical circuit and a control circuit, wherein the main circuit and the control circuit are integrated in a DC circuit. In the main circuit are the anode high voltage source with the anode 6 and the current controller, the current controller with the device controller, the electronic control system with the electronic control system, the electronic control system with the cathode high voltage source and the cathode high voltage source in parallel with the cathodes 40, 41, 42 and electrically connected to the respective grating device 43. In the control loop, the anode high-voltage source is electrically connected to the control system via a feedback loop. Here, the control system for both the sequential circuits of the cathodes 40, 41, 42, for the regulation of

Extraction grid electrodes 71, 73, 74 and the focusing electrodes 72, 76, 56 of the respective grating device 43 and provided for the control of the main circuit current, wherein the electrical voltage of the cathode high voltage source is adaptable to the master circuit predetermined by the control system.

In FIG. 21, eight cathodes 41, 42 of the MBFEX tube 1 are outlined by way of example. Both the first type cathodes 41 and the second type cathodes 42 have Carbon nanotubes, however, differ in terms of their geometry. The cathodes 41, 42 are arranged in rows in the vacuum tube 20 and alternately staggered, the number of cathodes 41 of the first type being equal to the number of cathodes 42 of the second type. A grating device 43 and thus a

X-ray source Q may each be associated with a cathode 41 of the first form and a respective cathode 42 of the second form. In the MBFEX tube 1 according to FIG. 21, the cathodes 41 of the first type or the cathodes 42 of the second type can be activated sequentially in any desired manner. In this way, dual-dose X-ray images with the MBFEX tube 1 can be realized.

As can be seen from FIGS. 22 to 25, a plurality of MBFEX tubes 1 can be combined into a rigid, annular or polygonal arrangement which replaces a rotating arrangement in a computer tomograph. This applies to any embodiment of MBFEX tubes 1 already described and explained below.

A layer structure of an emitter arrangement 44 of a MBFEX tube 1 is illustrated in FIGS. 12 to 20. The emitter assembly 44 comprises as the lowest layer a ceramic plate 45 made of corundum. The cathodes 40 are on a conductive coating of the ceramic board 45 and are manufactured by screen printing with high geometric precision. On the back of the ceramic board 45 conductor structures 66 can be seen.

On the ceramic board 45, a metal intermediate plate 46 is placed. This metal intermediate plate 46 has rectangular openings 61 for the cathodes 40. In addition, 46 are in the metal intermediate plate strip-shaped, compared to the

Openings 61 narrower and longer openings 62 on the longitudinal sides of the openings 61. The strip-shaped openings 62 have a function in the degassing of the vacuum tube 20. This applies both to the preparation of the operation and for the ongoing operation of the X-ray tube 1, respectively in cooperation with the Ceramic plate 45.

In the ceramic board 45 40 different strip-shaped openings 64, 65 can be seen in addition to the cathode. Here are three short, narrow openings 64 directly in addition to the longitudinal sides of each cathode 40. In addition, the cathodes 40 are flanked by somewhat further away, likewise strip-shaped openings 65. In each case, two strip-shaped openings 65 are arranged in a line one behind the other. Two pairs of such lines on striped openings 65, together with the intervening array of cathode 40, describe a total of six smaller ones

strip-shaped openings 64 in total an H-shape. This applies to all cathodes 40 on the ceramic board 45 with the exception of the two outermost cathodes 40, which are flanked only on one side by strip-shaped openings 65 of the longer type.

In particular, the internal openings 64, which are very close to the cathodes 40, contribute to the fact that during the emission of electrons gas can be discharged even in extremely low concentrations down to individual particles to the back of the emitter assembly 44. This is a major contribution to the prevention of flashovers within the vacuum tube 20 is made. For sucking off gas during the production of the x-ray tube 1, in particular during heating, the relatively large strip-shaped openings 65 are required to a greater extent.

The metal intermediate plate 46 has as an integral part of a connection strip 63 as from the emitter assembly 44 led to the outside electrical connection. On the metal intermediate plate 46 is a grid plate 47, which comprises the extraction grid electrodes 71, each having a cathode with a precisely defined distance of

0.224 mm (in the example of FIG. 12) are preset.

Details of the extraction grid electrode 71 will be apparent from FIG. Overall, the extraction grid electrode 71 has a rectangular shape whose longitudinal sides are formed by completely straight edge strips 78. The two edge strips are connected to one another by a multiplicity of grid strips 77, so that overall the grid structure results. In contrast to the edge strips 78, however, the grid strips 77 are not completely straight. Rather, at the two ends of each grid strip 77, that is, at the transition to the edge strip 78, a rounded transition region 79 is formed. The rounded transition regions 79 significantly ensure that thermally induced deformations do not a change in the distance between the cathode 40 and the extraction grid 71, but within the in-plane extraction grating 71 are recorded without affecting the emission properties of the emitter array 44.

The grid plate 47 is covered by an upper insulating layer 48 in the form of a plate made of a ceramic material, whereby the emitter assembly 44 is completed. The upper insulating layer 48, as shown in Fig. 12, has openings 49 adapted to the shape of the cathodes 40 to allow the passage of electrons.

Geometric features of the cathode 40, as contained multiple times in the emitter array 44, are shown in FIG. With good approximation, the cathode 40 is cuboid. Over the entire electron-emitting surface of the cathode 40, there are thus hardly any fluctuations in the distance between the cathode 40 and the extraction grid electrode 71 not shown in FIG. For comparison, the surface structure of a conventional cathode produced in the process of electrophoretic deposition (EPD) is indicated by dashed lines in FIG. A smooth surface can not be mentioned in this comparative example. Rather, pronounced peaks are present within the surface of the emission cathode, especially at the edges of the cathode produced in the EPD process. The electrons are emitted mainly at these tips. This limits on the one hand the lifetime and on the other hand the transmission rate at electrons. In contrast, the cathode 40 used in the X-ray tube 1 of the present invention emits electrons in each surface portion of its surface at a nearly constant release rate.

An exemplary embodiment of an anode 30 cooperating with the emitter arrangement 44 is illustrated in FIGS. 26 and 27. On the cylindrical base body of the anode 30 are several top pieces 33, which are also referred to as anode tops or short essays. Each of these essays 33 has a relation to the

Base obliquely coated, with tungsten or other suitable for X-ray sources material coated surface 34. The inclinations of the different surfaces 34 are different from each other, that - as indicated in Fig. 27 - the emitted X-ray X is focused in the direction of lying in the examination area U isocenter of the X-ray array 10.

List of Reference MBFEX tube

carrier

X-ray emitter arrangement

vacuum tube

X window

anode

Coolant discharge pipe

Coolant supply pipe

top section

coated surface

cathode

Cathode of a first kind

Cathode of a second kind

grating device

emitter array

ceramic board

Intermediate metal plate

grid plate

upper insulating layer

Opening in the upper insulating layer of the cathode feed line 51 high voltage feedthrough

52 high voltage feedthrough

61 Opening in the metal intermediate plate

62 strip-shaped opening in the metal intermediate plate

63 connection strips

64 narrow strip-shaped opening

65 wider strip-shaped opening

66 ladder structure

71 extraction grid electrode

72 focusing electrode

73 extraction grid electrode of a first form

74 extraction grid electrode of a second form

75 focusing electrode of a first form

76 focusing electrode of a second form

77 grid strips

78 edge stripes

79 rounded transition area

80 ceramic carrier

81 metal layer

AC anode current

E electron beam

e Electron main emission direction EC emitter current

GEV grid-emitter voltage

Q. X-ray source

X X-ray beam x X-ray main emission direction

U examination area

Claims

claims

1. MBFEX tube (1) for an X-ray machine, which in a vacuum tube (20) has a fixed therein, as well as a cooling finger formed anode (30) and a plurality of fixed cathodes (40,41,42), wherein the vacuum tube (20) has a plurality of cathode leads (50) and not more than two

High voltage bushings (51,52), in one

High-voltage bushing (52) a coolant pipe (31) is passed with an inner coolant inner tube (32), the coolant tube (31) and the coolant inner tube (32) for cooling the anode (30) provided with a liquid coolant are provided, the cathodes (40,41,42) for field emission of electrons and each aligned with the anode (30) for generating X-ray sources (Q.).

2. MBFEX tube (1) according to claim 1, characterized in that the cathode leads (50) and high-voltage bushings (51,52) in a row and the anode (30) are arranged opposite one another on the vacuum tube (20).

3. MBFEX tube (1) according to claim 2, characterized in that the

X-ray sources (Q.) are arranged in rows on the anode (30).

4. MBFEX tube (1) according to claim 3, characterized in that the

X-ray sources (Q.) in each case on a relative to the central axis of the anode (30) inclined surface portion of the anode (30).

5. MBFEX tube (1) according to claim 4, characterized in that the obliquely

surface sections are formed by attachments of the anode (30).

6. MBFEX tube (1) according to claim 4, characterized in that the obliquely

surface sections are formed by grinding in the anode (30).

7. MBFEX tube (1) according to claim 5 or 6, characterized in that the inclined surface portions of the anode (30) are coated.

8. MBFEX tube (1) according to one of claims 1 to 7, characterized in that the cathodes (40,41,42) have nanorods.

9. MBFEX tube (1) according to claim 8, characterized in that at least a part of the nanorods is formed as single- or multi-walled carbon nanotubes or single- or multi-walled hetero-nitrogen carbon nanotubes.

10. MBFEX tube (1) according to claim 8 or 9, characterized in that at least a part of the nanorods contains borides of rare earths, metal oxides, metal sulfides, nitrides, carbides or silicon.

11. MBFEX tube (1) according to any one of claims 8 to 10, characterized in that the nanorods have a length of less than 20 μιη and a diameter of less than 10 nm, wherein on the surface of the cathode ((40, 41, 42) density of at least 10 ⁶ nanorods per cm ² .

12. MBFEX tube (1) according to one of claims 1 to 11, characterized in that between at least one of the cathodes (40,41,42) extraction grid (71) and the anode (30) focusing electrodes (72) are arranged ,

13. MBFEX tube (1) according to claim 12, characterized in that the

Focusing electrodes (72) are grounded separately from the extraction grid (71).

14. MBFEX tube (1) according to claim 12 or 13, characterized in that the

Focusing electrodes (72) and / or extraction grille (71) made of steel, in particular stainless steel, are made.

15. MBFEX tube (1) according to any one of claims 12 to 14, characterized in that the extraction grid (71) describes a rectangular shape with two mutually parallel edge strips (78) which are integrally connected by grid strips (77), wherein the transitions between the grid strip (77) and the edge strip (78) rounded transition regions (79) are formed, with which the grid strip (77) each describe an elongated S-shape.

16. MBFEX tube (1) according to any one of claims 1 to 15, characterized in that the vacuum tube (20) has different types of cathodes (40,41,42), which with respect to at least one parameter from a group of

Parameters differ, where the group of parameters geometric

Includes parameters and material parameters.

17. MBFEX tube (1) according to any one of claims 1 to 16, characterized in that at least one type of cathode (40,41,42) for emission of Electron-formed layer having a thickness of less than 20 μιη and a Mittenrauwert (Ra) of less than 2.5 μιη is formed.

18. MBFEX tube (1) according to one of claims 1 to 17, characterized in that a plurality of cathodes (40,41,42) on a flat support member (45) are arranged.

19. MBFEX tube (1) according to claim 18, characterized in that the flat

Carrier element (45) has corundum.

20. MBFEX tube (1) according to claim 18 or 19, characterized in that the flat carrier element strip-shaped openings (64) of the first kind and strip-shaped openings (65) of the second type, wherein a group of strip-shaped openings (64) of the first kind closer is arranged adjacent to a cathode (40) as a group of strip-shaped openings (65) of the second kind, and wherein the strip-shaped openings (64) of the first kind are narrower than the strip-shaped openings (65) of the second type.

21. MBFEX tube (1) according to one of claims 18 to 20, characterized in that the flat carrier element (45) is part of a layered structure

Emitter assembly (44), which further comprises a metal intermediate plate (46), a grid plate (47) including extraction grid (71), and an upper insulating layer (48).

22. MBFEX tube (1) according to claim 21, characterized in that strip-shaped openings (64,65) of the planar support element (45) at least partially aligned with openings (62) in the metal intermediate plate (46).

23. MBFEX tube (1) according to one of claims 1 to 22, characterized in that the anode (30) is designed for two-sided supply and discharge of coolant, wherein at both ends of the anode (30) each have a coolant supply line and a assigned coolant discharge is arranged.

24. MBFEX tube (1) according to any one of claims 1 to 23, characterized in that the anode (30) at least partially surrounds an examination area (U), wherein the X-ray sources (Q.) Enclose the examination area (U) also at least partially ,

25. MBFEX tube (1) according to claim 24, characterized in that the anode (30) is arcuate.

26. MBFEX tube (1) according to one of claims 1 to 24, characterized in that the anode (30) is designed as a rotating anode.

27. Arrangement of a plurality of MBFEX tubes (1) designed according to claim 1, wherein a ring, arc, polygon, L, or Form is formed.

28. A method for producing a MBFEX tube (1) according to claim 1, wherein a

Vacuum tube (20), an anode (30) to be placed in the vacuum tube (20), and cathodes (40, 41, 42) for field emission of electrons, also to be arranged in the vacuum tube (20), and at least one between the Cathodes (40,41,42) and the anode (30) to be arranged element, which is selected from the group of elements comprising an extraction grating (71) and a focusing electrode (72) is processed by laser.

29. The method according to claim 28, characterized in that the laser processing of the element (71,72) takes place with picosecond or femtosecond clocking of the laser.

A method of operating an MBFEX tube (1) according to claim 1, wherein the anode (30) is used to emit successive X-ray pulses of different wavelengths.