Silicon field effect emitter

Abstract

The invention relates to a silicon field effect emitter. The invention relates to an X-ray tube, an X-ray apparatus, a method for generating X-ray radiation with a predefined spatial distribution on an anode, and a related computer program product. The X-ray tube according to the invention has: - an anode, - a first switching device, - a second switching device, - a control unit, and - an emitter with a plurality of field effect emitter needles, wherein at least one of the plurality of field effect emitter needles has a diameter of less than 1 pm and is made of silicon, wherein a first group of the plurality of field effect emitter needles can be switched on or off by means of the first switching device, wherein a second group of the plurality of field effect emitter needles can be switched on or off by means of the second switching device, wherein the first group is different from the second group, and wherein the control unit is configured to control the first switching device and the second switching device.

Description

Technical Field

[0001] The present invention relates to an X-ray tube, an X-ray apparatus, a method for generating X-ray radiation on an anode in a predetermined spatial distribution, and related computer program products. Background Technology

[0002] In an X-ray tube, X-ray radiation is typically generated by bombarding the anode with electrons. The resolving power of an X-ray tube is generally determined by the spatial distribution of electrons striking the anode. Electrons are traditionally emitted by thermionic tungsten emitters, carbon field-effect emitters, and / or field-effect emitters with diffused cathodes. A common feature of the emitters described above is that the electron emission density is typically limited to approximately 3 A / cm². However, for imaging examinations, an electron emission density of approximately 10 A / cm² is usually required, thus electrons from conventional emitters are typically focused onto the anode, particularly using deflection units. The focusing of electrons generally depends on the accelerating voltage between the cathode and anode, as well as the electron space charge density. That is, the spatial distribution of electrons typically varies depending on the accelerating voltage and / or the intensity of the electron beam.

[0003] An electron emission device having at least one electron emission electrode and at least one blocking gate is known from the unpublished application EP 18158898.

[0004] Unpublished application EP 18154147 discloses a thermionization device having a planar emitter and an accessible field-effect electron emitter.

[0005] In “Silicon Field Emitter Arrays With Current Densities Exceeding 100 A / cm² at Gate Voltages Below 75 V” (IEEE ELECTRON DEVICE LETTERS, VOL.37, NO.1, JANUARY 2016), Guerrera et al. described a silicon field-effect emitter with an electron emission density exceeding 100 A / cm². Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an X-ray tube, an X-ray device, a method for generating X-ray radiation on an anode in a predetermined spatial distribution, and related computer program products, wherein the emission of electrons is more flexibly controlled.

[0007] The aforementioned technical problems are solved by the features of this invention. Advantageous design solutions are given in the following description.

[0008] The X-ray tube according to the present invention has:

[0009] -anode,

[0010] -First switchgear,

[0011] -Second switchgear

[0012] -Control unit, and

[0013] - An emitter with multiple field-effect emitter needles,

[0014] Among them, at least one of the multiple field-effect emitter pins has a diameter of less than 1 μm and is made of silicon.

[0015] The first group of multiple field-effect emitter pins can be switched on or off using a first switching device.

[0016] The second group of multiple field-effect emitter pins can be switched on or off using a second switching device.

[0017] Among them, the first group is different from the second group, and

[0018] The control unit is configured to control the first switching device and the second switching device.

[0019] The emitter is preferably constructed with multiple field-effect emitter needles according to the silicon field-effect emitter of Guerrera et al. In particular, at least one field-effect emitter needle may have a diameter between 10 nm and 800 nm, preferably between 100 nm and 500 nm, particularly advantageously between 150 nm and 250 nm, for example, 200 nm. At least one field-effect emitter needle typically contains no carbon and / or is made only of silicon. In principle, it is conceivable that each field-effect emitter needle has silicon and / or is made of silicon. In particular, the emitter has between 2 and 25,000,000 field-effect emitter needles per square millimeter, preferably between 100,000 and 10,000,000. The multiple field-effect emitter needles are typically spaced between 10 nm and 500 μm, preferably between 200 nm and 1 μm, relative to each other. The multiple field-effect emitter needles are typically oriented in parallel.

[0020] Typically, at least one field-effect emitter, preferably each field-effect emitter, can be switched on using a gate-emitter voltage, particularly greater than 0V, less than 1kV, preferably less than 200V, and particularly advantageously less than 100V. In particular, the gate-emitter voltage forces an electric field at the tip of the switched-on field-effect emitter, causing the switched-on field-effect emitter to emit electrons. Specifically, the first and / or second groups can be switched off by applying a gate-emitter voltage equal to or less than 0V.

[0021] Specifically, the anode can be a vertical anode (stehanode) or a rotating anode. For example, the anode may contain tungsten for generating X-ray radiation from electrons. A rotating anode may be part of a rotating piston X-ray tube or a rotating anode X-ray tube. The X-ray tube is typically evacuated. To accelerate electrons emitted by the switched-on field-effect emitter needle, an accelerating voltage is typically applied between the emitter and the anode. This accelerating voltage is provided, for example, by a power supply voltage. The X-ray tube, for example, has a power supply voltage for applying a first accelerating voltage or a second accelerating voltage between the emitter and the anode. The first accelerating voltage may be different from or the same as the second accelerating voltage. Preferably, the control unit can control a first switching device or a second switching device based on the applied accelerating voltage.

[0022] Preferably, multiple field-effect emitters can be switched on or off in groups, particularly in an alternating manner. The first and / or second groups typically include at least one field-effect emitter from a plurality of field-effect emitters, up to 100% of the plurality of field-effect emitters. The first and second groups typically differ in at least one field-effect emitter. In principle, it is conceivable that the first and second groups have at least partially identical field-effect emitters. The intersection of the first and second groups may not be zero. Alternatively, the intersection may be empty. The first and second groups are not identical. In principle, it is conceivable that the second group includes field-effect emitters that are turned off during the simultaneous on-state of the first group of field-effect emitters. Alternatively or additionally, the second group preferably includes field-effect emitters that are turned on or off in a time-staggered manner relative to the plurality of field-effect emitters in the first group. Typically, the field-effect emitters of the first group and the field-effect emitters of the second group are turned on or off alternately.

[0023] Typically, multiple field-effect emitters are arranged in a distributed manner in two spatial directions and / or in a grid pattern. Multiple field-effect emitters are usually arranged such that the emitters are two-dimensional. Advantageously, multiple field-effect emitters are arranged in a single plane and / or oriented parallel to each other. In principle, it is conceivable to arrange multiple field-effect emitters linearly or in a multidimensional manner.

[0024] The envelope of the first group of field-effect emitter pins (Umhüllende) may at least partially overlap with the envelope of the second group of field-effect emitter pins. In particular, the midpoint of the envelope of the first group of field-effect emitter pins may lie inside the envelope of the second group of field-effect emitter pins. The midpoint of the envelope of the first group of field-effect emitter pins and the midpoint of the envelope of the second group of field-effect emitter pins may be substantially the same. The envelope specifically includes the outermost connected field-effect emitter pins of the respective group, and / or particularly forms a rectangle or circle. In particular, the envelope is an envelope line (Einhüllende). The field-effect emitter pins of the first group typically intersect at least partially with the field-effect emitter pins of the second group.

[0025] It is conceivable that each field-effect emitter needle has a switch, which is connected to a first switching device and / or a second switching device. The switch can be the field-effect emitter needle power supply voltage (power supply) used to provide the gate-emitter voltage. In particular, the first and second switching devices can be logically mapped in a programmable device, and more particularly, the switches of multiple field-effect emitter needles can electronically switch the emission of electrons at the corresponding field-effect emitter needles. In particular, if the first and second switching devices are logically mapped, it is preferable that the first and second groups can repeatedly occupy multiple field-effect emitter needles. In other words, the control unit can advantageously select, for example, field-effect emitter needles for the first group and / or field-effect emitter needles for the second group according to a measurement protocol. In this case, it is preferable that the X-ray tube can be used for different measurement protocols without needing to reconnect the field-effect emitter needles electronically. In particular, the groups of multiple field-effect emitter needles can be controlled by means of a control unit, such that the control unit programs the first and / or second switching devices using the corresponding switches of the first and / or second groups.

[0026] The electron emission switch can correspond to the on / off state of the first group and / or the second group. The electron emission switch can include, particularly, complete cutoff of electron emission when off, and / or, particularly, stepless adjustment of electron emission when on. Stepless adjustment of electron emission can correspond to setting the emission current of the corresponding on field-effect emitter pin. Stepless adjustment can be related to the gate-emitter voltage.

[0027] In particular, the switching on and off of the field-effect emitter needle can be repeated at frequencies higher than 0.1 Hz, advantageously higher than 10 kHz, and especially advantageously higher than 1 MHz, preferably time-staggered group-related switches. High-frequency switching is particularly advantageous compared to thermionic emitters because the heat distribution inside the emitter can be effectively controlled, and / or the total number of emitted electrons, especially the total emission current as the sum of the emission currents, can be flexibly adjusted.

[0028] A first switching device is associated with the first group, in particular, via the switch of a corresponding field-effect emitter pin of the first group, and / or a second switching device is associated with the second group, in particular, via the switch of a corresponding field-effect emitter pin of the second group. This association corresponds in particular to an electronic connection. Specifically, a control unit is configured to control the first and second switching devices such that, for example, by issuing a first on signal, the first switching device activates the first group of field-effect emitter pins, in particular, activates its switch, and / or, for example, by issuing a second on signal, the second switching device activates the second group of field-effect emitter pins, in particular, activates its switch. Specifically, the first switching device can activate those field-effect emitter pins of the first group according to the on signal, for example, by activating the switch of the field-effect emitter pins of the first group. As an alternative to activation, control additionally includes deactivation, for example, by issuing a deactivation signal.

[0029] X-ray tubes constructed in this manner can advantageously provide the electron emission density required for imaging examinations, particularly preferably an electron emission density of approximately 10 A / cm² at the anode. Here, it is preferable to activate only a portion of the multiple field-effect emitting electrodes, such as a first or second group. If not all field-effect emitting electrodes are activated, especially if the heat generation within the emitters is uniformly distributed, this is advantageous, for example, for the lifespan of the X-ray tube, particularly for emitters with multiple field-effect emitting electrodes. A longer lifespan is particularly advantageous for cost reduction.

[0030] X-ray tubes advantageously lack an electron beam deflection unit between the emitter and anode. Conventional electron beam deflection units typically include magnetic deflection units. Advantageously, a first and / or second set is chosen in terms of quantity and / or arrangement such that the X-ray tube does not require an electron beam deflection unit between the emitter and anode. Consequently, the weight of the X-ray tube is significantly less than that of a conventional X-ray tube with a deflection unit. In this case, the X-ray tube is generally less expensive than a conventional X-ray tube. Furthermore, it is preferable that electron beam control is simplified if the X-ray tube is less complex due to the absence of a deflection unit.

[0031] Multiple field-effect emitting electrodes can be grouped and / or switched, particularly enabling the switching of field-effect emitting electrodes according to different measurement protocols used for imaging examinations, wherein, preferably, the spatial distribution of electrons on the anode remains unchanged. Different measurement protocols may differ, particularly in accelerating voltage, X-ray radiation dose, and / or resolving power. For example, the manufacturers and / or users and / or physicians of the X-ray tubes can determine the number of field-effect emitting electrodes in a first group and / or a second group. Determining the corresponding group of field-effect emitting electrodes can correspond to the programming of the emitters. Advantageously, in addition to the first and second groups, other groups of field-effect emitting electrodes can also be determined. Preferably, the control unit can determine the number of switching devices and the field-effect emitting electrodes grouped together with the corresponding switching devices according to the measurement protocol.

[0032] Furthermore, the grouping of field-effect emitters allows for flexible electron beam shapes. Particularly advantageously, the arrangement of the first and second groups of field-effect emitters ensures that the predetermined spatial distribution of electrons striking the anode is substantially independent of the group being activated.

[0033] One implementation is configured such that the first and second groups differ in the arrangement of the plurality of field-effect emitters. The arrangement is particularly inconsistent with respect to the reference point. If the field-effect emitters of the two groups differ in arrangement, the shape of the electron beam is typically affected, particularly by the physical interactions of the emitted electrons relative to each other, thereby affecting the spatial distribution of the electrons. Considering the physical interactions, it is preferable to make it possible to omit the deflection unit. The physical interactions include, in particular, electrostatic effects arising from the space charge density of the electrons. The arrangement of the switched-on field-effect emitters can be, for example, star-shaped, circular, or arbitrary.

[0034] One implementation is configured such that the first group and the second group differ in the number of multiple field-effect emitter pins. If the number varies, the arrangement will typically be different automatically. The variation in the number of multiple field-effect emitter pins in the respective groups preferably allows for scaling of the emission current.

[0035] One implementation is configured such that the first group and the second group have different applied accelerating voltages. This implementation is particularly advantageous because, depending on the accelerating voltage, the heat distribution can be distributed across the field-effect emitter needles.

[0036] The arrangement and / or number of field-effect emission needles and / or the applied accelerating voltage, for example, can be determined in a simulation of the X-ray tube or by test measurements of the X-ray tube, and / or stored in the storage unit of the control unit in a group-specific manner.

[0037] A preferred embodiment is configured such that the first group and the second group differ in the number and arrangement of the plurality of field-effect emitting electrodes and the applied accelerating voltage. In this embodiment, it is advantageous to consider the physical interactions between emitted electrons, particularly due to space charge density, such that the spatial distribution of electrons on the anode is identical regardless of which switching devices are switched on. In other words, in this embodiment, electrons advantageously strike the anode with the same spatial distribution, regardless of which field-effect emitting electrodes are switched on. Another advantage is that the X-ray radiation dose generated by the electrons is independent of the switched field-effect emitting electrodes, whereas the X-ray radiation dose is typically related to the applied accelerating voltage. In particular, the X-ray radiation dose corresponds to the intensity of the X-ray radiation.

[0038] One embodiment is configured such that a first switching device and / or a second switching device are configured to turn on a plurality of corresponding field-effect emitter pins, such that each turned-on field-effect emitter pin provides a saturation current. This embodiment is particularly advantageous if the first group and the second group differ in the number of the plurality of field-effect emitter pins. In this case, the total emitter current is typically related to the number of turned-on field-effect emitter pins. In particular, the total emitter current can be flexibly controlled. According to Guerrera et al., the saturation current can be determined by the specific structure of the plurality of field-effect emitter pins, wherein the specific structure particularly includes the effective cross-section and / or doping density of the respective field-effect emitter pins, and / or the electron saturation rate. Operating the field-effect emitter needle in saturation is particularly advantageous because it keeps the emission current of the corresponding switched-on field-effect emitter needle constant. In other words, especially in the absence of stepless current control, the control of the first and second switching devices involves the binary control of either the first or second group. The switch operates as follows. In saturation, the corresponding switched-on field-effect emitter pin provides a constant current independently of the applied electric field. Specifically, the corresponding switched-on field-effect emitter pin has a current limit. Compared to silicon field-effect emitters, conventional carbon field-effect emitters may be damaged by excessive electric fields because conventional carbon field-effect emitters typically do not have a current limit. In this embodiment, the emitter current cannot typically be steplessly adjusted. The gate-emitter voltage is preferably greater than or equal to the saturation voltage.

[0039] The X-ray apparatus according to the invention comprises an X-ray tube and an X-ray detector. The X-ray detector advantageously detects the X-ray radiation emitted during imaging examinations of a patient. For example, medical images can be reconstructed using the detected X-ray radiation. Medical images can be provided to a user or physician on a display unit, and / or stored in a radiology information system and / or a PACS image archiving system, for example. The X-ray apparatus can be configured, in particular, as a conventional X-ray system, as a single-source computed tomography (CT) device, as a mammography system, or as a C-arm angiography system.

[0040] One embodiment is configured such that the X-ray device is used for imaging examinations using an alternating accelerating voltage. Specifically, the alternating accelerating voltage is pre-defined according to a dual-energy-message protocol. The accelerating voltage preferably alternates at a frequency greater than 1 Hz, preferably greater than 100 Hz, and particularly advantageously greater than 1 kHz. Another advantage of this embodiment is that the alternating accelerating voltage can be rapidly switched using a corresponding set of field-effect emitting electrodes. In this embodiment, substances within the patient's body, which typically have an attenuation coefficient as a function of the accelerating voltage, can be distinguished, for example. In particular, these substances can be tissue and / or bone and / or contrast agents. Specifically, the X-ray device has only a single X-ray tube, preferably without additional X-ray tubes as in conventional dual-energy X-ray devices. In other words, imaging examinations according to the dual-energy-message protocol do not require additional X-ray tubes.

[0041] The method according to the invention for generating X-ray radiation on an anode in a predetermined spatial distribution comprises the following steps:

[0042] -The spatial distribution of electrons striking the anode of the X-ray tube is predetermined.

[0043] -Based on the accelerating voltage, select a group of multiple field-effect emitter needles for the X-ray tube's emitter.

[0044] - By switching on a selected set of multiple field-effect emitting electrodes, X-ray radiation is generated on the anode in a pre-defined spatial distribution.

[0045] Spatial distribution specifically corresponds to modulation-transfer-funktion. For example, users and / or physicians can pre-define the spatial distribution using input devices, particularly keyboards, mice, and / or screens. Alternatively, control units can automatically determine the spatial distribution, for example, based on measurement protocols pre-defined by the user and / or physician.

[0046] The selection of groups may include, in particular, determining the arrangement, especially the number of multiple field-effect emitting electrodes. Preferably, the selection of groups is performed automatically, for example, in a control unit, particularly according to a measurement protocol pre-defined by the user and / or physician.

[0047] The control unit, in particular, can turn on a selected group of multiple field-effect emitter pins, for example, by means of a switching device and / or a switch of the corresponding field-effect emitter pins. Turning on may include applying a gate-emitter voltage. By turning on the selected group of multiple field-effect emitter pins, electrons are emitted, and the electrons are directed onto the anode, such that X-ray radiation is generated when the electrons, preferably in a predetermined spatial distribution, strike the anode.

[0048] A computer program product may be a computer program, or may include a computer program. In particular, the computer program product has program code means reflecting the method steps according to the invention. Thus, the method according to the invention can be defined and executed in a repeatable manner, and control can be applied via the transfer of the method according to the invention. Preferably, the computer program product is configured such that a computing unit can execute the method steps according to the invention by means of the computer program product. In particular, the program code means can be loaded into the memory of the computing unit, and typically the memory is accessed by the processor of the computing unit to execute the program code means. If the computer program product, particularly the program code means, is executed in the computing unit, all embodiments of the described method according to the invention can generally be executed. For example, the computer program product can be stored on a physical computer-readable medium, and / or digitally stored as data packets in a computer network. The computer program product can be a physical computer-readable medium and / or a data packet in a computer network. Therefore, the invention may also relate to a physical computer-readable medium and / or a data packet in a computer network. For example, by inserting the physical computer-readable medium into a DVD drive or into a USB port, the physical computer-readable medium can typically be directly connected to the computing unit, whereby the computing unit can access the physical computer-readable medium, particularly in a read-only manner. Preferably, data packets can be retrieved from a computer network. Computer networks can have computing units, or they can be indirectly connected to computing units via wide area network (WAN) connections or (wireless) local area network (WLAN or LAN) connections. For example, computer program products can be digitally stored on a cloud server at a storage location on the computer network, and in particular, transmitted to the computing unit via the Internet and / or via WLAN or LAN by calling a download link pointing to the storage location of the computer program products.

[0049] Features, advantages, or alternative embodiments mentioned in the description of the device can also be applied to the method, and vice versa. In other words, features of the method can be extended using features of the device, and vice versa. In particular, the device according to the invention can be used in the method. Attached Figure Description

[0050] The invention will now be described and explained in more detail with reference to embodiments shown in the accompanying drawings. In principle, in the following description of the drawings, substantially identical structures and elements are named using the same reference numerals as when the corresponding structures or elements first appear.

[0051] Figure 1 The emitter of a plurality of field-effect emitter needles with a first group is shown in the first embodiment.

[0052] Figure 2 The emitter of the second embodiment having a second set of multiple field-effect emitter needles is shown.

[0053] Figure 3 The trajectories of the emitted electrons are shown in relation to the applied accelerating voltage.

[0054] Figure 4 The X-ray device in the third embodiment is shown, and

[0055] Figure 5 A method for generating X-ray radiation on an anode in a pre-defined spatial distribution is shown. Detailed Implementation

[0056] Figure 1 A top view of the emitter E with a first group G1 of multiple field-effect emitter needles F1, F2, and FN is shown in the first embodiment. The multiple field-effect emitter needles F1, F2, and FN are arranged in a manner distributed in two spatial directions, and in this embodiment, there are 8 × 10 field-effect emitter needles.

[0057] The first group G1 has multiple field-effect emitter pins F1, F2, and FN marked with a cross, and in this embodiment includes 12 field-effect emitter pins. That is, the first quantity is 12. In principle, it is conceivable that the first group has more or less than 12 field-effect emitter pins. If the control unit S controls and connects to... Figure 1 In the switching device not shown, the multiple field-effect emitter pins F1, F2, and FN of the first group G1 emit electrons. These electrons are accelerated by a first accelerating voltage, which is, for example, between 30 kV and 150 kV, preferably 120 kV.

[0058] The first group G1 has a first arrangement and a first number of multiple field-effect emitter pins F1, F2, and FN, which are particularly related to Figure 2 The embodiments shown are different.

[0059] Figure 2 A top view of the emitter E with a second group G2 and multiple field-effect emitter needles F1, F2, and FN is shown in the second embodiment. The second group G2 differs from the first group G1. The second group G2 has a second arrangement and a second number of multiple field-effect emitter needles F1, F2, and FN. The second number is 20. The multiple field-effect emitter needles F1, F2, and FN in the second group G1 are marked with dashed crosshairs.

[0060] Electrons emitted by the second group of G2 are accelerated by a second accelerating voltage, which is, for example, between 30kV and 150kV, preferably 80kV.

[0061] With Figure 1 Compared to the first group of G1 field-effect emitter pins connected in the middle, in Figure 2 The field-effect emitter pins of the second group of G2 connected in the middle are arranged more compactly.

[0062] Preferably, the circuit can be switched on sequentially or at different times, according to a dual-energy measurement protocol. Figure 1 and Figure 2 The multiple field-effect emitter needles shown are grouped G1 and G2.

[0063] Figure 3 The trajectories of emitted electrons associated with accelerating voltages applied at temporal intervals are schematically illustrated. In particular, if by means of… Figure 3 The power supply voltage of the field-effect emitter pin (not shown) correspondingly provides the gate-emitter voltage, thus emitting electrons. With the aid of the power supply voltage V, electrons emitted from the emitter E are preferably accelerated towards the anode A in a vacuum.

[0064] The solid and dashed trajectories differ in the number of field-effect emitting electrodes used for emission, and thus in the effect of their physical interaction with each other. When Figure 1 The first quantity is less than Figure 2 For the second quantity, the solid line trajectory is shown, for example. Figure 1 The electronic design shown is illustrated by the dashed line trace. Figure 2 The electronic design shown. Due to... Figure 2 The illustrated embodiment has a larger emission current and a larger space charge density, which in turn results in relatively stronger physical interactions between electrons, so the dashed trajectories run at greater distances from each other compared to the solid trajectories.

[0065] Figure 4An X-ray tube R according to a third embodiment is shown. The X-ray tube R has an anode A, a first switching device, a second switching device, a control unit S, and an emitter E having a plurality of field-effect emitter needles F1, F2, and FN. At least one of the plurality of field-effect emitter needles F1, F2, and FN has a diameter of less than 1 μm and is made of silicon. The plurality of field-effect emitter needles F1, F2, and FN in a first group G1 can be switched on or off by means of the first switching device. The plurality of field-effect emitter needles F1, F2, and FN in a second group G2 can be switched on or off by means of the second switching device. The first group G1 is different from the second group G2. The control unit S is configured to control the first and second switching devices. The control unit S can be part of the X-ray tube R or can be disposed outside the X-ray tube R. In particular, the control unit S can have an FPGA or a processor. In this embodiment, the control unit S is disposed outside the X-ray tube R and connected to the X-ray tube R to control the first and second switching devices.

[0066] In principle, it is conceivable that the first switching device and / or the second switching device are configured to enable the switching of the respective plurality of field-effect emitter pins F1, F2, FN such that each switched field-effect emitter pin provides a saturation current.

[0067] The X-ray device has an X-ray tube R and an X-ray detector D, wherein the X-ray device is configured for imaging examinations using alternating accelerating voltages. Specifically, during the imaging examination, the accelerating voltage preferably alternates according to a dual-energy measurement protocol. In this embodiment, the X-ray device is shown as part of a single-source computed tomography (CT) device. The patient P is supported on a patient bed L.

[0068] Figure 5 A flowchart is shown for a method of generating X-ray radiation on an anode in a pre-defined spatial distribution.

[0069] Method step S100 means: the spatial distribution of electrons that strike the anode of the X-ray tube is given in advance.

[0070] Method step S101 means: Select a group of multiple field-effect emitter needles of the X-ray tube emitter according to the accelerating voltage.

[0071] Method step S102 means: turning on a selected set of multiple field-effect emitting electrodes, thereby generating X-ray radiation on the anode in a predetermined spatial distribution.

[0072] Although the present invention has been described and illustrated in detail with reference to preferred embodiments, the present invention is not limited to the disclosed examples, and those skilled in the art can derive other variations therefrom without departing from the scope of protection of the present invention.

Claims

1. A method for generating X-ray radiation at the anode (A) of an X-ray tube (R) in a predetermined spatial distribution, wherein, The X-ray tube (R) further comprises a first switching device, a second switching device, a control unit (S), and an emitter (E) having a plurality of field-effect emitter needles (F1, F2, FN), wherein at least one of the plurality of field-effect emitter needles (F1, F2, FN) has a diameter of less than 1 μm and is made of silicon, wherein a first group (G1) of the plurality of field-effect emitter needles (F1, F2, FN) can be switched on or off by means of the first switching device, wherein the second switching device can be switched on or off by means of the second switching device. A switching device connects or disconnects a second group (G2) of the plurality of field-effect emitter pins (F1, F2, FN), wherein the first group (G1) and the second group (G2) differ in the arrangement and number of the plurality of field-effect emitter pins (F1, F2, FN) and in the applied accelerating voltage, wherein the first group (G1) and the second group (G2) have at least partially identical field-effect emitter pins, and wherein the control unit (S) is configured to control the first switching device and the second switching device. The method includes the following steps: -The spatial distribution of electrons that strike the anode (A) is given in advance. -In the control unit (S), groups (G1, G2) are selected based on the acceleration voltage. - Turn on multiple field-effect emitting electrodes (F1, F2, FN) of the selected group (G1, G2), thereby generating X-ray radiation on the anode (A) in a predetermined spatial distribution.

2. An X-ray tube (R) configured to perform the method according to claim 1.

3. An X-ray device, the X-ray device comprising: - The X-ray tube (R) according to claim 2, and - X-ray detector (D).

4. The X-ray apparatus according to claim 3, wherein, The X-ray device is configured to perform imaging examinations using alternating accelerating voltages.

5. A computer program product capable of being directly loaded into the memory of a computing unit, having program code means for executing the method according to claim 1 when the computer program product is executed in the computing unit.

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