COMPUTER TOMOGRAPHY APPARATUS AND METHOD FOR OPERATION OF COMPUTER TOMOGRAPHY APPARATUS - Patent application

Abstract

A computed tomography apparatus includes a static beamer-detector ring (10) composed of an odd number (n) of beamer-detector elements (11, 12, 13, 14, 26), wherein a single beamer-detector element (26) among the beamer-detector elements (11, 12, 13, 14, 26) is displaceable relative to the remaining beamer-detector elements (11, 12, 13, 14) that together form a C-shape while opening the beamer-detector ring (10), and each beamer-detector element (11, 12, 13, 14, 26) emits X-ray radiation. and a detector (4) extending over an angle β of at least 0.95×360° / n within the same beamer-detector element (11, 12, 13, 14, 26) for detecting X-ray radiation, wherein each anode assembly (9) is part of a beamer assembly (18) including a plurality of electron emitters (5, 25), each of which is located at a focal point (BF - ,BF,BF + ) are formed at at least three selectable positions on the anode assembly (9) in cooperation with the electrode assembly (21) forming the anode assembly (9).

Description

[Technical field]

[0001] The present invention relates to a computer tomography apparatus with a static beamer-detector ring, i.e. a beamer-detector ring that does not rotate during operation of the computer tomography apparatus, and further to a method for operating such a computer tomography apparatus.

[0002] The computer tomography apparatus can basically be operated with a rotating beamer-detector unit or with an X-ray emitter and a corresponding detector arranged in a fixed position. Possible configurations of a computer tomography apparatus with a non-rotating beamer-detector unit are described in WO 2018 / 086744.

[0003] EP 1 474 040 discloses an imaging device for X-ray technology, which comprises a gantry frame on which an X-ray radiation source and a corresponding detector are rotatably supported. Of the generally annular gantry, one segment is removable in order to allow the object to be imaged to be positioned in the central imaging area of ​​the gantry ring. Guide devices for the radiation source and the detector are also found in the removable segment.

[0004] Another X-ray technology device with a generally annular beamer-detector arrangement which includes a movable segment for the purpose of opening the annulus is described in US Pat. No. 6,113,264. The movable segment can in this case be shifted in the circumferential direction of the annular beamer-detector arrangement.

[0005] The documents US Pat. No. 7,001,045 and EP-A-3,646,793 describe various configurations of computer tomography apparatus with variously adjustable annular beamer-detector modules.

[0006] Totally movable computed tomography devices are described, for example, in the documents WO 2010 / 078481 and DE 10 2016208123 A1.

[0007] DE 10 2010028438 A1 describes an X-ray technology device configured as a C-arm device with carbon nanotubes as electron emitters. Scanning trajectories can be realized by means of a number of X-ray radiation sources arranged at different spatial positions, which are described in detail in DE 10 2010028438 A1.

[0008] The problem on which the invention is based is to provide an improved X-ray technique imaging means with a static beamer-detector ring compared to the prior art, which allows good handling and very good image quality in a device structure that is not overly complex.

[0009] The above-mentioned problem is solved according to the invention by a computer tomography apparatus having the features of claim 1. Similarly, the problem is solved by a method for operating a computer tomography apparatus according to claim 11. The features and advantages of the invention described below in relation to the operating method also apply to the apparatus, i.e. the computer tomography apparatus, and vice versa.

[0010] The computer tomography apparatus comprises a static beamer-detector ring made up of an odd number n of beamer-detector elements, a single beamer-detector element of which can be shifted relative to the remaining beamer-detector elements which together form a C-shape while opening up the beamer-detector ring, each beamer-detector element having an anode assembly arranged to emit X-ray radiation and extending over an angle α of at least 0.9×360° / n around the circumference of the beamer-detector ring, and a detector arranged to detect X-ray radiation and extending over an angle β of at least 0.95×360° / n within the same beamer-detector element, each anode assembly being part of a beamer assembly including a plurality of electron emitters, in which each electron emitter is , electric At least three selectable positions on the anode assembly in cooperation with the pole assembly One of To configured to form a focal point In this case, the selectively adjustable positions of the focal spot which can be produced by the same electron emitter are in particular arranged in line in the circumferential direction of the beamer-detector ring, i.e. at different angular positions around the central axis of the computer tomography device, in particular at equal intervals. The switching between the different focal spot positions by stepwise changing the setting of the electrode assemblies is called beam toggling.

[0011] The present application provides an operating method for the use of a computer tomography apparatus, the computer tomography apparatus comprising a non-rotating beamer-detector ring, the beamer-detector ring being composed of an odd number of beamer-detector elements or segments, one of which is configured to open the beamer-detector ring, a plurality of electron emitters being arranged on both the fixed and open beamer-detector elements, the electron emitters each forming a focal spot at a variable position on an anode corresponding to a beamer-detector element by means of an electrode controlling an electron beam, such that the total number of possible focal spots corresponds to a multiple of the number of electron emitters, the maximum angular separation between two focal spots juxtaposed in the same beamer-detector element in the circumferential direction of the beamer-detector ring is smaller than the minimum angular separation between focal spots of two adjacent beamer-detector elements, the method comprising: - positioning a beamer-detector ring in the circumferential direction of the examination object, in which the beamer-detector ring is first opened and then closed at the latest in a position provided for carrying out an X-ray technical examination; - directing a fan-shaped X-ray beam bundle from the first focal point towards an object to be inspected and detecting the X-ray radiation by a detector of at least two beamer-detector elements; - forming a second focal point around the circumference of the beamer-detector ring, the second focal point being offset by a first differential angle with respect to the first focal point, not necessarily located directly next to the first focal point; - forming further focal points around the circumference of the beamer-detector ring, each offset by a predetermined differential angle with respect to the previous focal point, where the differential value between two successive differential angles is smaller than the difference between the minimum angular separation between focal positions of adjacent beamer-detector elements and the maximum angular separation between two adjacent focal positions within the same beamer-detector element; The present invention relates to a method comprising the steps of:

[0012] The invention is based on the consideration that a computer tomography device with an openable beamer-detector ring offers advantages over conventional computer tomography devices with a beamer-detector ring that is permanently closed during preparation for an X-ray technique exposure. For example, the openable beamer-detector ring can be pushed laterally above the patient's lying table in the open state. The construction that allows a large number of focal positions and at the same time reduces the mass, despite the availability of a means for opening the beamer-detector ring, is supported by the selective adjustment of different focal positions for each electron emitter. The anodes arranged around the circumference of the beamer assembly occupy, as a whole, at least 90% of this circumference, i.e. 324°. Due to the odd number of beamer-detector elements, the abutment points between two beamer-detector elements are never exactly diagonally opposite a similar abutment point. If a focal point is present in the edge region of the beamer-detector element, i.e. near the abutment point, the X-ray radiation from this focal point impinges on two circumferentially juxtaposed X-ray detectors, for example photon-counting detectors. In particular, the use of linear detectors is considered. In this regard, reference is made to WO 2019 / 057339. In general, scintillation detectors, which may be of any shape, can be used as X-ray detectors. Compared to the anode of the beamer-detector ring, the detector extends over a larger angle in each case, i.e. over at least 95% of the circumference, i.e. over an angle of at least 342° in total, divided for the individual segments of the beamer-detector ring.

[0013] Compared to the smallest possible angular interval between focal positions at adjacent beamer-detector elements, the possible focal positions within the same beamer-detector element are scaled much more closely. If all possible focal positions were selected in the circumferential direction of the beamer-detector ring in sequence, then there would be a regular shift towards a smaller number of angular intervals, i.e. when switching from one beamer-detector element to the next, there would be significantly larger jumps in the angle settings. The operating method of the present application results in an equalization of the angular intervals between one focal position and the next in time. Here, the successive switching between the different focal positions allows the description of several rotations around the central axis of the beamer-detector ring, with all possible focal positions being occupied only after several rotations. In particular, the focal points are formed in each individual rotation with mutually different settings of the electrodes controlling the electron beam. This means, for example, that during rotation of the virtual X-ray source, a first electrode assembly is set so that the electron beam remains in a neutral average alignment state, whereas a second electrode assembly corresponding to another electron emitter is controlled so that the corresponding electron beam is deflected in a specific direction compared to the neutral alignment state, which is accompanied by an offset of the focal spot around the circumference of the beamer-detector ring.

[0014] The continuous adjustment of the angular setting of the X-ray radiation during operation of the computer tomography device, i.e. the switching between the different possible focal positions, is explained below on the basis of a simplified numerical example.

[0015] The beamer-detector ring consists of only three beamer-detector elements, each of which extends over an angle of about 120°. The abutment point between the first and third beamer-detector elements is at the 0° position. The centers of the three segments are therefore located at 60°, 180° and 300° (in the circumferential direction of the beamer-detector ring).

[0016] For simplicity, it is assumed that each beamer-detector element has only two electron emitters, where the electron beam emitted from one emitter can be directed to the corresponding anode assembly in three different ways.

[0017] The electron beam is oriented with respect to the anode in an average alignment state, or in a clockwise deflection state, or in a counterclockwise deflection state, with the deflection state orientation relative to the circumferential direction of the beamer-detector ring.

[0018] The uniform spacing between the possible focal positions in the first beamer-detector element is given, for example, at focal positions of 20°, 36°, 52°, 68°, 84°, 100°. Here, the first three values ​​are assigned to the first electron emitter, and the values ​​68°, 84°, 100° are assigned to the second electron emitter. The average alignment state of the electron beam corresponds to a focal position of 36° (first electron emitter) or a focal position of 84° (second electron emitter). In the numerical example discussed here, based on a very small number of electron emitters, the electron beam can be deflected in comparison with the respective average alignment state such that each focal position occurs at a deviation of ±16° with respect to the focal position occurring in the average alignment state of the electron beam. This results in an angular spacing of always 16° between the focal position located in the first beamer-detector element and the next possible focal position in the same beamer-detector element.

[0019] Similarly, the focal position in the second beamer-detector element can be selected at 140°, 156°, 172°, 188°, 204°, 220° and the focal position in the third beamer-detector element can be selected at 260°, 276°, 292°, 308°, 324°, 340°. The first beamer-detector element is represented by an open segment of the beamer-detector ring. The second beamer-detector element is fixedly connected to the third beamer-detector element. Despite the fact that the beamer-detector elements differ from one another in terms of their mechanical function, all beamer-detector elements are configured to be equal in terms of their X-ray technical function, in particular the arrangement of the focal spot on the X-ray source, i.e. the anode, as well as the arrangement of the X-ray detector. Therefore, when performing and evaluating a computer tomography, i.e. an X-ray technical examination, it is not necessary to take into account to what extent one beamer-detector element can be adjusted with respect to the remaining beamer-detector elements.

[0020] In order to guarantee the desired alignment of one of the beamer-detector elements and at the same time design all beamer-detector elements similarly with respect to their X-ray technology function, each anode assembly is only partially able to utilize the construction space of 120° available in each beamer-detector element. Therefore, between the outermost possible focal position of one beamer-detector element and the focal position of the next beamer-detector element which is the closest thereto, there is an angular interval that is much larger than the angular interval between focal positions in the same beamer-detector element. In this example, the minimum angular intervals between the focal positions of the different beamer-detector elements which result in an overlap with the next element are: between the first element (20°) and the third element (340°), there is an angular interval of 40°, between the first element (100°) and the second element (140°), and also between the second element (220°) and the third element (260°).

[0021] Now, if all possible focal positions are set in a clockwise (or counterclockwise) sequence, thereby simulating a mechanical rotation of the X-ray source around the longitudinal axis of the computed tomography device, then five angle changes of 16° each are always followed by an angle change of 40°, which are then followed by five jump changes also of 16°.

[0022] Such non-uniformity in the angle jumps can be avoided by applying a new pattern in which different focus positions are set in sequence.

[0023] Starting from the first possible focus position in the clockwise direction, i.e. the 20° position, six virtual rotations are started, where in a simplified example only three focus positions are selected in sequence, which are offset from one another by 120° on average in each rotation. In particular, the possible sequence of focus positions is 20°, 140°, 276°, 52°, 172°, 308°, 84°, 204°, 340°, 100°, 220°, 324°, 68°, 188°, 292°, 36°, 156°, 260°, so that each of the total 18 possible focus positions is selected exactly once after the six virtual rotations. In this case, the difference from the average angular interval of 120° is less than 16° either above or below, where eight angular intervals of 120° occur, and five angular intervals of 136° or 104° occur, never going from the value 104° to the value 136° (or vice versa). This also applies to the six virtual rotation restarts, i.e. alternations from the 260° position to the 20° position, which correspond to a difference angle of exactly 120°.

[0024] Thus, in the simplified example considered, only three different values ​​of the difference angle appear, namely 104°, 120° and 136°, where the difference value between two consecutive difference angles, i.e. 0° or 16°, is smaller than the angular interval between mutually adjacent foci of two beamer-detector elements. In fact, the difference value in this case is smaller than 1 / 2 of the above-mentioned angular interval of 40° extending across the segment boundary. However, even if the uniform angular interval of 16° height in the segment in the described example is subtracted from the angular interval across the segment, a difference of 24° occurs, which is even larger than the maximum difference value that occurs between temporally consecutive difference angles. This allows transillumination of the examination object with X-ray radiation in the form of a fan-shaped beam bundle emanating from each focal point with a relatively uniform angular change simulating the rotation of the X-ray source, despite the uneven distribution of focal points around the circumference of the beamer-detector ring, which occurs due to the segmentation of the beamer-detector ring and its opening mechanism.

[0025] Each focal spot is arranged on an anode assembly, which may include one or more liquid-cooled or uncooled anodes per X-ray tube. For example, the anodes are used in a similar manner as described in DE 102017008810 A1. Independent of the anode geometry, the computer tomography device can be configured such that each beamer-detector element simultaneously forms two or more mutually offset focal spots on the circumference of the beamer-detector ring. If a volume of interest is examined with exactly two focal spots and correspondingly two bundles of X-ray beams, a stereotactic method of X-ray technology imaging can also be used.

[0026] With regard to the geometric configuration of the cathode used as an electron emitter in a computed tomography device, it is possible to select, for example, the measures selected in International Publication No. 2019 / 057338, which claims priority to the above-mentioned patent application DE 102017008810 A1.

[0027] The drive control means which can also be used in this example are described, for example, in WO 2019 / 042587. For the manufacture of a cathode arranged to emit electrons, it is possible to use, for example, any of the solutions given in the documents WO 2018 / 086737 and WO 2018 / 141485.

[0028] Overall, the X-ray tube of the computed tomography device can be configured to generate X-ray pulse trains that differ from one another in terms of various parameters, in particular the duration, intensity and X-ray dose of the individual pulses as well as the frequency of the X-ray radiation. For this purpose, in particular the formation of a variation in the voltage applied to the anode and the formation of a variation in the electron current emitted from the cathode can be envisaged. These means of forming a variation associated with the X-ray source show their advantages in particular in combination with photon-counting detectors that are respectively suitable for distinguishing between different X-ray frequencies, i.e. for multi-energy and multi-dose operating modes.

[0029] The computer tomography device may be a mobile device or a stationary X-ray technology device and is particularly suitable for the examination of the breast area.

[0030] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 is a schematic diagram showing a computer tomography device. [Diagram 2] FIG. 2 is a view similar to FIG. 1 showing the computed tomography apparatus with the beamer-detector ring in an open state. [Diagram 3] FIG. 2 is an enlarged view showing details of the computer tomography device. [Figure 4] FIG. 2 is an enlarged view showing details of the computer tomography device. [Diagram 5]FIG. 1 illustrates an X-ray tube of a computer tomography device. [Figure 6] FIG. 1 illustrates an X-ray tube of a computer tomography device. [Figure 7] FIG. 1 illustrates an X-ray tube of a computer tomography device. [Figure 8] FIG. 1 shows a beamer-detector element of a computed tomography device, consisting of an X-ray tube and a corresponding detector. [Figure 9] FIG. 2 is a schematic diagram showing details of a computer tomography device. [Figure 10] FIG. 2 is a schematic diagram showing details of a computer tomography device.

[0032] The computed tomography apparatus generally designated by reference number 1 comprises a stationary gantry 2, where the term "stationary" is to be understood as meaning that there is no rotation of the beamer-detector unit about the central axis MA of the gantry 2 during the acquisition of X-ray technical images. Instead, the X-ray tubes 3 and the corresponding X-ray detectors 4 distributed all around the circumference of the gantry 2 can form a fan-shaped bundle of X-ray radiation RS emanating from a focal point BF on the anode 6 of the X-ray tube 3, respectively. A number of cathodes 5, 25 are respectively assigned to each of the individual X-ray tubes 3 as electron emitters. In the illustrated example, a single elongated anode 6 is provided for all X-ray tubes 3, which in this case is simultaneously considered as an anode assembly 9. Alternatively, the anode assembly 9 of the X-ray tube 3 may consist of a number of anodes 6.

[0033] The gantry 2 is mounted in a variably adjustable manner on a movable frame 7. In particular, the gantry 2 can be tilted about a horizontal tilt axis perpendicular to the central axis MA. Likewise, the gantry 2 can be shifted in the longitudinal direction of the horizontally disposed central axis MA. Furthermore, the circumferential position adjustment of the gantry 2 can be limited. Means are also provided for raising and lowering the entire gantry 2. In addition to the movable frame 7, a separate operation evaluation unit 8 is also present in this example. A structural integration of the movable frame 7 and the operation evaluation unit 8 is also conceivable.

[0034] No housing is provided that encloses the gantry 2. Rather, the entire gantry 2 is configured as a beamer-detector ring 10, which is formed from a total of five beamer-detector elements 11, 12, 13, 14, 26. Here, the beamer-detector elements 11, 12, 13, 14 are fixed elements that are immovably connected to one another, whereas the beamer element 26 is shiftable in order to open the beamer-detector ring 10. The opening is performed in order to enclose the patient couch 15 by the beamer-detector ring 10. The opening mechanism is configured as a shift mechanism 16. Starting from a closed beamer-detector ring 10, as shown in FIG. 1, the beamer-detector element 26 is first shifted somewhat in the longitudinal direction of the central axis MA, i.e. lifted out of the beamer-detector ring 10. With the beamer-detector element 26 positioned next to the C-shaped arrangement of the remaining beamer-detector elements 11, 12, 13, 14, the beamer-detector element 26 can be shifted in the circumferential direction of the C-shaped arrangement 11, 12, 13, 14, which opens an opening on the circumference of the beamer-detector ring 10, as shown in FIG. 2. No tilting of the beamer-detector element 26 with respect to the remaining beamer-detector elements 11, 12, 13, 14 occurs at any time. Due to the absence of a tilting mechanism associated with the beamer-detector element 26, the available construction space, which extends over an angle of 72° on the circumference of the beamer-detector ring 10, is consistently available for the integration of X-ray technology components, as will be mentioned in more detail below.

[0035] With regard to the arrangement of the X-ray technology components, the shiftable beamer-detector element 26 does not differ from the fixed beamer-detector elements 11, 12, 13, 14. Each beamer-detector element 11, 12, 13, 14, 26 has a uniform structure, which is shown in Figs. 5 to 8. The connecting members of the X-ray tube 3 are marked with the reference number 17. The beamer assembly 18 of the X-ray tube 3 emits X-ray radiation RS, as shown in Fig. 4, so that it always hits two of the five beamer-detector elements 11, 12, 13, 14, 26 (more precisely its detector 4). Due to the odd number of beamer-detector elements 11, 12, 13, 14, 26, the abutment point between two beamer-detector elements 11, 12, 13, 14, 26 is never exactly diagonally opposite to such second abutment point.

[0036] In each X-ray tube 3 there is a group of emitter modules 19 which form an electron beam ES which impinges on the anode assembly 9 and thus forms a focal point BF. The focal point BF does not necessarily have to have an approximately point-like shape. Instead, for example, an elongated focal point BF can also be formed in a manner which is fundamentally known, the position of the focal point BF being understood in each case as the position of its centre point.

[0037] In this embodiment, the emitter modules 19 each include different cathodes 5, 25 for producing X-ray radiation of different doses and / or different wavelengths. In each case, electrons are extracted from the cathodes 5, 25 by an extraction grid 20, whereupon the electron beam ES can be deflected in a defined manner by an electrode assembly 21 including a number of electrodes 22, 23. The cathodes 5, 25 are commonly arranged on a board 24.

[0038] The entire anode assembly 9 cooperating with the emitter modules 19 of the X-ray tube 3 extends over an angle α around the circumference of the beamer-detector ring 10 which is significantly smaller than 72°. The angle β describing the extension of the X-ray detectors 4 around the circumference of the beamer-detector ring is much closer to 72°. In other words, the gaps formed between the individual X-ray detectors 4 around the circumference of the beamer-detector ring 10 are significantly narrower than the gaps formed between the beamer assemblies 18. A large number of possible focal positions extend within the X-ray tube 3 over an angle γ which is smaller than the angle α.

[0039] The electrode assembly 21 selectively directs the electron beam ES to a focal point BF or to a focal point BF offset relative to the focal point BF in the circumferential direction of the beamer-detector ring 10. + ,B.F. - 9 and 10, the focal point BF + is clockwise around the focus BF, and - The deflection of the electron beam ES, which means the offset of the focal point BF, is also called beam toggling, and the offset of the focal point BF around the circumference of the beamer-detector ring 10. - ,BF,BF + In this case, a total number of several hundred focal positions, which corresponds to a multiple of the number of electron emitters 5, 25, can be achieved. [Explanation of symbols]

[0040] 1. Computer tomography equipment 2 Gantry 3 X-ray tube 4. X-ray detector 5. First type cathode, electron emitter 6 Anode 7. Exercise frame 8 Operational Evaluation Unit 9 Anode Assembly 10 Beamer-detector ring 11 Fixed first beamer-detector element 12 Fixed second beamer-detector element 13 Fixed third beamer-detector element 14 Fixed fourth beamer-detector element 15 Patient Bed 16 Shift mechanism 17 Connection parts 18 Beamer Assembly 19 Emitter Modules 20 Extraction grid 21 Electrode Assembly 22,23 electrode 24 Board 25 Second type cathode, electron emitter 26 Shiftable Beamer-Detector Elements α the angle over which the anode assembly of the beamer-detector element extends β Angle of extension of the detector of the beamer-detector γ Angular range within which the possible focal points of the anode assembly are located BF Focus (General) BF + ,B.F. - The focal spot formed by the electron emitter (average position and two offset positions around the circumference of the beamer-detector ring) ES Electron Beam MA center axis RS X-ray

Claims

1. 1. A computer tomography apparatus comprising: a static beamer-detector ring (10) made up of an odd number (n) of beamer-detector elements (11, 12, 13, 14, 26), a single beamer-detector element (26) of said beamer-detector elements (11, 12, 13, 14, 26) being displaceable relative to the remaining beamer-detector elements (11, 12, 13, 14) which together form a C-shape while opening up said beamer-detector ring (10); Each beamer-detector element (11, 12, 13, 14, 26) has an anode assembly (9) arranged to emit X-ray radiation and extending over an angle α of at least 0.9×360° / n around the circumference of said beamer-detector ring (10), and a detector (4) arranged to detect X-ray radiation and extending over an angle β of at least 0.95×360° / n within the same beamer-detector element (11, 12, 13, 14, 26); Each anode assembly (9) is part of a beamer assembly (18) that includes a plurality of electron emitters (5, 25) in which each electron emitter (5, 25) is configured to cooperate with an electrode assembly (21) to form a focal spot at one of at least three selectable locations on the anode assembly (9); Between the mutually most distant focal points of the same anode assembly (9), an angle γ of at least 0.85×α is formed around the circumference of the beamer-detector ring, so that from each possible focal point position, a fan-shaped X-ray beam bundle is alignable to at least two beamer-detector elements (11, 12, 13, 14, 26) diametrically opposite the focal points in the beamer-detector ring (10). Computer tomography equipment.

2. 2. The computer tomography apparatus of claim 1, wherein the beamer-detector element (26) displaceable relative to the remaining beamer-detector ring (10) is shiftable in the axial direction of the beamer-detector ring (10) and, in a state shifted in the axial direction, is shiftable in the tangential direction along the beamer-detector elements (11, 12, 13, 14) which are arranged generally in a C-shape.

3. 3. The computer tomography apparatus according to claim 1 or 2, wherein the beamer-detector element (11, 12, 13, 14, 26) comprises an emitter (5, 25) configured for field emission of electrons, in particular an emitter comprising carbon nanotubes.

4. 4. The computer tomography apparatus according to claim 3, wherein each beamer-detector element (11, 12, 13, 14, 26) comprises at least one emitter (5) of a first type and at least one emitter (25) of a second type.

5. 5. The computer tomography device according to claim 4, wherein emitters of different types (5, 25) within one beamer-detector element (11, 12, 13, 14, 26) differ from one another with regard to their material and / or geometry.

6. the beamer-detector elements (11, 12, 13, 14, 26) are configured for switching between different X-ray frequencies and / or different X-ray doses; Each focal spot is similarly selectable as a source of all possible X-ray frequencies and X-ray doses; 6. A computer tomography apparatus according to claim 3.

7. 7. The computer tomography apparatus according to claim 1, wherein the beamer-detector ring (10) is adjustably mounted on a movable instrument frame (7).

8. the beamer-detector ring (10) includes at least five and up to nine beamer-detector elements (11, 12, 13, 14, 26); all beamer-detector elements (11, 12, 13, 14, 26), including the displaceable beamer-detector element (26), cover an angular range of the same size; 8. A computer tomography apparatus according to any one of claims 1 to 7.

9. 9. The computer tomography apparatus according to claim 1, wherein the beamer-detector elements (11, 12, 13, 14, 26) are configured to simultaneously form at least two focal points offset from one another around the circumference of the beamer-detector ring (10).

10. A method for operating a computer tomography device (1), comprising the steps of: the computed tomography device (1) comprises a non-rotating beamer-detector ring (10), the beamer-detector ring (10) being composed of an odd number of beamer-detector elements (11, 12, 13, 14, 26), a single element (26) of the beamer-detector elements (11, 12, 13, 14, 26) being configured to open the beamer-detector ring (10); a plurality of electron emitters (5, 25) are arranged on the fixed beamer-detector elements (11, 12, 13, 14) and also on the beamer-detector elements (26) which are open to the fixed beamer-detector elements (11, 12, 13, 14), said electron emitters (5, 25) respectively form focal spots at variable positions on the anode (6) corresponding to each beamer-detector element (11, 12, 13, 14, 26) by means of electrodes (21, 22, 23) which control the electron beam, so that the total number of possible focal spots corresponds to a multiple of the number of electron emitters (5, 25); a maximum angular interval between two focal positions arranged side by side in the same beamer-detector element (11, 12, 13, 14, 26) in the circumferential direction of the beamer-detector ring (10) is smaller than a minimum angular interval between focal positions of two adjacent beamer-detector elements (11, 12, 13, 14, 26); The method further comprising: - positioning said beamer-detector ring (10) in the circumferential direction of the examination object, in which said beamer-detector ring (10) is closed at the latest in a position provided for carrying out an X-ray technical examination; - directing a fan-shaped X-ray beam bundle emerging from a first focal point towards said object under examination and detecting the X-ray radiation by a detector (4) of at least two beamer-detector elements (11, 12, 13, 14, 26); - forming a second focal point around the circumference of the beamer-detector ring (10) and offset relative to the first focal point by a first differential angle; - forming further focal points around the circumference of the beamer-detector ring (10), each offset by a predetermined differential angle with respect to the previous focal point, where the differential value between two successive differential angles is smaller than the difference between the minimum angular separation between focal positions of adjacent beamer-detector elements (11, 12, 13, 14, 26) and the maximum angular separation between two adjacent focal positions within the same beamer-detector element (11, 12, 13, 14, 26); Including, Each beamer-detector element (11, 12, 13, 14, 26) has an anode assembly (9) arranged to emit X-ray radiation and extending over an angle α of at least 0.9×360° / n around the circumference of said beamer-detector ring (10); Between the mutually most distant focal points of the same anode assembly (9), an angle γ of at least 0.85×α is formed around the circumference of the beamer-detector ring, so that from each possible focal point position, a fan-shaped X-ray beam bundle is alignable to at least two beamer-detector elements (11, 12, 13, 14, 26) diametrically opposite the focal points in the beamer-detector ring (10). method.

11. 11. The method according to claim 10, wherein multiple rotations are described around the central axis (MA) of the beamer-detector ring (10) by successively switching between different focus positions, and only after multiple rotations are all possible focus positions considered to have been occupied.

12. 12. The method according to claim 11, wherein in each individual rotation a focal spot is formed at mutually different settings of electrodes (21, 22, 23) which control respectively different electron beams.

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