COMPUTER TOMOGRAPH AND METHOD FOR OPERATING A COMPUTER TOMOGRAPH

Abstract

A computer tomograph includes a static radiator-detector ring, which is constructed from an odd number of radiator-detector elements, of which a single one is displaceable, with opening of the radiator-detector ring. The displaceable element the other radiator-detector elements together defining a C-shape. Each radiator-detector element has an anode arrangement for the emission of X-rays, which extends over an angle α of at least 0.9×360°/n on the circumference of the radiator-detector ring. A detector is provided for detection of X-ray radiation, which extends within the same radiator-detector element over an angle β of at least 0.95×360°/n. Each anode arrangement is part of a radiator arrangement including multiple electron emitters, in which each electron emitter is configured, in cooperation with an electrode arrangement, to generate a focal spot at one of at least three selectable positions on the anode arrangement.

Claims

1. A computer tomograph, comprising a static radiator-detector ring, which is constructed from an odd number of radiator-detector elements, of which a single radiator-detector element is displaceable, with opening of the radiator-detector ring, the displaceable radiator-detector element with the remaining radiator-detector elements together defining a C-shape, wherein each radiator-detector element has an anode arrangement provided for the emission of X-rays, which extends over an angle α of at least 0.9×360°/n on a circumference of the radiator-detector ring, and a detector provided for the detection of X-ray radiation, which extends within the same radiator-detector element over an angle β of at least 0.95×360°/n, and wherein each anode arrangement is part of a radiator arrangement comprising a plurality of electron emitters, in which each electron emitter is configured, in cooperation with an electrode arrangement, to generate a focal spot at one of at least three selectable positions on the anode arrangement.

2. The computer tomograph as claimed in claim 1, wherein the emitter-detector element displaceable in relation to the remaining emitter-detector ring is displaceable in an axial direction of the emitter-detector ring and, in an axially displaced state, is slidable in a tangential direction along the radiator-detector elements arranged overall in a C-shape.

3. The computer tomograph as claimed in claim 1, wherein the emitter-detector elements have emitters configured for field emission of electrons, in particular emitters comprising carbon nanotubes.

4. The computer tomograph as claimed in claim 3, wherein each emitter-detector element has at least one emitter of a first type and at least one emitter of a second type.

5. The computer tomograph as claimed in claim 4, wherein the different emitter types within a radiator-detector element differ from one another with regard to materials and/or geometry.

6. The computer tomograph as claimed in claim 3, wherein the emitter-detector elements are configured for switching between different X-ray frequencies and/or X-ray doses, wherein each focal spot is equally selectable as a source of all settable X-ray frequencies and X-ray doses.

7. The computer tomograph as claimed in claim 1, wherein the radiator-detector ring is attached in an adjustable manner to a movable device frame.

8. The computer tomograph as claimed in claim 1, wherein the emitter-detector ring comprises at least five radiator elements and at most nine radiator elements, wherein all radiator-detector elements, including the displaceable radiator-detector element, cover angular ranges of equal size.

9. The computer tomograph as claimed in claim 1, wherein between most distant focal spots of the same anode arrangement, an angle γ of at least 0.85× α is enclosed on the circumference of the radiator-detector ring and from each of the possible focal spot positions a fan-shaped X-ray beam is alignable on at least two radiator-detector elements diametrically opposite to the focal spot on the radiator-detector ring.

10. The computer tomograph as claimed in claim 1, wherein the radiator-detector elements are configured to simultaneously generate at least two mutually offset focal spots on the circumference of the radiator-detector ring.

11. A method for operating a computer tomograph, which comprises a non-rotating radiator-detector ring which is constructed from an odd number of radiator-detector elements, of which a single element is configured to open the radiator-detector ring, wherein a plurality of electron emitters is arranged both in the fixed radiator-detector elements and in the radiator-detector element to be opened, which are each configured, with the aid of electrodes influencing electron beams, to generate a focal spot having a variable position on an anode associated with the radiator-detector element, so that a total number of possible focal spot positions corresponds to a multiple of the number of electron emitters, and wherein the maximum angular distance between two focal spot positions arranged adjacent to one another within the same radiator-detector element in the circumferential direction of the radiator-detector ring is less than the minimum angular distance between focal spot positions of two adjacent radiator-detector elements, comprising the following steps: Positioning the radiator-detector ring around an examination object, wherein the radiator-detector ring is closed, at the latest, in a position provided for carrying out an X-ray examination, Directing a fan-shaped X-ray beam, which originates from a first focal spot, onto the examination object, wherein X-ray radiation is detected by detectors of at least two radiator-detector elements, Generating a second focal spot, which is offset by a first differential angle in relation to the first focal spot on the circumference of the radiator-detector ring, Generating further focal spots, which are each offset on the circumference of the radiator-detector ring in relation to the previous focal spot by a differential angle, wherein a differential absolute value between two successive differential angles is less than a difference between a minimum angular distance between focal spot positions in adjacent radiator-detector elements and a maximum angular distance between two adjacent focal spot positions within the same radiator-detector element.

12. The method as claimed in claim 11, wherein multiple revolutions around the central axis of the emitter-detector ring are defined by successive switching between different focal spot positions, wherein all possible focal spot positions have only been assumed after a plurality of revolutions.

13. The method as claimed in claim 12, wherein focal spots are generated in mutually differing settings of different electrodes influencing electron beams during each individual revolution.

14. The computer tomograph as claimed in claim 1, wherein the emitter-detector elements have emitters comprising carbon nanotubes configured for field emission of electrons.

1. A computer tomograph, comprising a static radiator-detector ring (10), which is constructed from an odd number (n) of radiator-detector elements (11, 12, 13, 14, 26), of which a single one (26) is displaceable, with opening of the radiator-detector ring (10), in relation to the remaining radiator-detector elements (11, 12, 13, 14) describing a C-shape together, wherein each radiator-detector element (11, 12, 13, 14, 26) has an anode arrangement (9) provided for the emission of X-rays, which extends over an angle α of at least 0.9×360°/n on the circumference of the radiator-detector ring (10), and a detector (4) provided for the detection of X-ray radiation, which extends within the same radiator-detector element (11, 12, 13, 14, 26) over an angle β of at least 0.95×360°/n, and wherein each anode arrangement (9) is part of a radiator arrangement (18) comprising multiple electron emitters (5, 25), in which each electron emitter (5, 25) is designed, in cooperation with an electrode arrangement, to generate a focal spot (BF.sup.−, BF, BF.sup.+) at one of at least three selectable positions on the anode arrangement (9).

2. The computer tomograph as claimed in claim 1, characterized in that the emitter-detector element (26) displaceable in relation to the remaining emitter-detector ring (10) is displaceable in the axial direction of the emitter-detector ring (10) and, in the axially displaced state, is slidable in the tangential direction along the radiator-detector elements (11, 12, 13, 14) arranged overall in a C-shape.

3. The computer tomograph as claimed in claim 1 or 2, characterized in that the emitter-detector elements (11, 12, 13, 14, 26) have emitters (5, 25) designed for field emission of electrons, in particular emitters comprising carbon nanotubes.

4. The computer tomograph as claimed in claim 3, characterized in that each emitter-detector element (11, 12, 13, 14, 26) has at least one emitter (5) of the first type and at least one emitter (25) of the second type.

5. The computer tomograph as claimed in claim 4, characterized in that the different emitter types (5, 25) within a radiator-detector element (11, 12, 13, 14, 26) differ from one another with regard to their materials and/or geometry.

6. The computer tomograph as claimed in any one of claims 3 to 5, characterized in that the emitter-detector elements (11, 12, 13, 14, 26) are designed for switching between different X-ray frequencies and/or X-ray doses, wherein each focal spot (BF.sup.−, BF, BF.sup.+) is equally selectable as the source of all settable X-ray frequencies and X-ray doses.

7. The computer tomograph as claimed in any one of claims 1 to 6, characterized in that the radiator-detector ring (10) is attached in an adjustable manner to a movable device frame (7).

8. The computer tomograph as claimed in any one of claims 1 to 7, characterized in that the emitter-detector ring (10) comprises at least five and at most nine radiator elements (11, 12, 13, 14, 26), wherein all radiator-detector elements (11, 12, 13, 14, 26), including the displaceable radiator-detector element (26), cover angular ranges of equal size.

9. The computer tomograph as claimed in any one of claims 1 to 8, characterized in that between the most distant focal spots (BF.sup.−, BF.sup.+) of the same anode arrangement (9), an angle γ of at least 0.85× α is enclosed on the circumference of the radiator-detector ring and from each of the possible focal spot positions (BF.sup.−, BF, BF.sup.+) a fan-shaped X-ray beam can be aligned on at least two radiator-detector elements (11, 12, 13, 14, 26) diametrically opposite to the focal spot on the radiator-detector ring (10).

10. The computer tomograph as claimed in any one of claims 1 to 9, characterized in that the radiator-detector elements (11, 12, 13, 14, 26) are designed to simultaneously generate at least two mutually offset focal spots (BF.sup.−, BF, BF.sup.+) on the circumference of the radiator-detector ring (10).

11. A method for operating a computer tomograph (1), which comprises a non-rotating radiator-detector ring (10) which is constructed from an odd number of radiator-detector elements (11, 12, 13, 14, 26), of which a single element (26) is designed to open the radiator-detector ring (10), wherein a plurality of electron emitters (5, 25) is arranged both in the fixed radiator-detector elements (11, 12, 13, 14) and in the radiator-detector element to be opened (26), which are each designed, with the aid of electrodes (21, 22, 23) influencing electron beams, to generate a focal spot (BF.sup.−, BF, BF.sup.+) having a variable position on an anode (6) associated with the radiator-detector element (11, 12, 13, 14, 26), so that the total number of possible focal spot positions corresponds to a multiple of the number of electron emitters (5, 25), and wherein the maximum angular distance between two focal spot positions arranged adjacent to one another within the same radiator-detector element (11, 12, 13, 14, 26) in the circumferential direction of the radiator-detector ring (10) is less than the minimum angular distance between focal spot positions of two adjacent radiator-detector elements (11, 12, 13, 14, 26), comprising the following steps: Positioning the radiator-detector ring (10) around an examination object, wherein the radiator-detector ring (10) is closed, at the latest, in a position provided for carrying out an X-ray examination, Directing a fan-shaped X-ray beam, which originates from a first focal spot (BF.sup.−, BF, BF.sup.+), onto the examination object, wherein X-ray radiation is detected by detectors (4) of at least two radiator-detector elements (11, 12, 13, 14, 26), Generating a second focal spot (BF.sup.−, BF, BF.sup.+), which is offset by a first differential angle in relation to the first focal spot (BF.sup.−, BF, BF.sup.+) on the circumference of the radiator-detector ring (10), Generating further focal spots (BF.sup.−, BF, BF.sup.+), which are each offset on the circumference of the radiator-detector ring (10) in relation to the previous focal spot (BF.sup.−, BF, BF.sup.+) by a differential angle, wherein the differential absolute value between two successive differential angles is less than the difference between the minimum angular distance between focal spot positions in adjacent radiator-detector elements (11, 12, 13, 14, 26) and the maximum angular distance between two adjacent focal spot positions within the same radiator-detector element (11, 12, 13, 14, 26).

12. The method as claimed in claim 11, characterized in that multiple revolutions around the central axis (MA) of the emitter-detector ring (10) are described by the successive switching between different focal spot positions, wherein all possible focal spot positions have only been assumed after a plurality of revolutions.

13. The method as claimed in claim 12, characterized in that focal spots (BF.sup.−, BF, BF.sup.+) are generated in mutually differing settings of different electrodes (21, 22, 23) influencing electron beams during each individual revolution.

Description

[0034] In the following, an exemplary embodiment of the invention will be described in greater detail with reference to a drawing. In the figures:

[0035] FIG. 1 shows a computer tomograph in an overview illustration,

[0036] FIG. 2 shows, in a representation analogous to FIG. 1, the computer tomograph having open radiator-detector ring,

[0037] FIGS. 3 and 4 show, in different enlargements, details of the computer tomograph,

[0038] FIGS. 5 to 7 show an X-ray tube of the computer tomograph,

[0039] FIG. 8 shows a radiator-detector element of the computer tomograph constructed from an X-ray tube and associated detector,

[0040] FIGS. 9 and 10 show schematic representations of details of the computer tomograph.

[0041] A computer tomograph identified overall by the reference sign 1 comprises a fixed gantry 2, wherein the term “fixed” is to be understood to mean that there is no rotation of an radiator-detector unit around the central axis MA of the gantry 2 when obtaining X-ray images. Rather, with the aid of X-ray tubes 3 distributed around the entire circumference of the gantry 2 and associated X-ray detectors 4, fan-shaped bundles of X-ray radiation RS can be generated, which each originate from a focal spot BF on an anode 6 of the X-ray tube 3. The individual X-ray tubes 3 each have multiple cathodes 5, 25 assigned as electron emitters. In the exemplary embodiment outlined, each X-ray tube 3 has a single, elongated anode 6 which, in this case, is also considered an anode arrangement 9. Alternatively, the anode arrangement 9 of an X-ray tube 3 can be constructed from a plurality of anodes 6.

[0042] The gantry 2 is attached to a movable frame 7 in a manner adjustable in multiple ways. Among other things, tilting of the gantry 2 around a horizontal tilting axis orthogonally intersecting the central axis MA is possible. Likewise, the gantry 2 can be displaced in the longitudinal direction of the horizontally arranged central axis MA. In addition, limited adjustments of the gantry 2 in its circumferential direction are also possible. There is also the possibility of raising or lowering the entire gantry 2. In the exemplary embodiment, a separate operating and evaluation unit 8 is present in addition to the movable frame 7. A structural combination of movable frame 7 and operating and evaluation unit 8 is also conceivable.

[0043] A housing enclosing the gantry 2 is not provided. Rather, the entire gantry 2 is constructed as an radiator-detector ring 10, which is formed from a total of five radiator-detector elements 11, 12, 13, 14, 26. In this case, the radiation detector elements 11, 12, 13, 14 represent fixed elements that are rigidly connected to one another, whereas the radiator element 26 is displaceable in order to open the radiator-detector ring 10. The opening takes place in order to enclose a patient table 15 using the radiator-detector ring 10. The opening mechanism is constructed as a slide mechanism 16. Starting from the closed radiator-detector ring 10, as shown in FIG. 1, the radiator-detector element 26 is initially displaced somewhat in the longitudinal direction of the center axis MA, i.e., raised out of the radiator-detector ring 10. In this state, in which the radiator-detector element 26 is positioned adjacent to the C-shaped arrangement of the remaining radiator-detector elements 11, 12, 13, 14, the radiator-detector element 26 can be displaced in the circumferential direction of the C-shaped arrangement 11, 12, 13, 14, whereby the opening at the circumference of the radiator-detector ring 10, as shown in FIG. 2, is released. Tilting of the radiator-detector element 26 in relation to the remaining radiator-detector elements 11, 12, 13, 14 does not occur at any time. Due to the lack of tilting mechanisms, with regard to the radiator-detector element 26, the available space, which extends over a 72° angle on the circumference of the radiator-detector ring 10, can largely be used for the installation of X-ray components, which will be discussed in more detail hereinafter.

[0044] With regard to the arrangement of X-ray components, the displaceable radiator-detector element 26 does not differ from the fixed radiator-detector elements 11, 12, 13, 14. Each radiator-detector element 11, 12, 13, 14, 26 has a uniform structure shown in FIGS. 5 to 8. Fittings of the X-ray tubes 3 are denoted by 17. Radiator assemblies 18 of the X-ray tubes 3 emit X-ray radiation RS in such a way that, as illustrated in FIG. 4, two of the five radiator-detector elements 11, 12, 13, 14, 26—more precisely: their detectors 4—are struck. Because of the odd number of the radiator-detector elements 11, 12, 13, 14, 26, a joint between two radiator-detector elements 11, 12, 13, 14, 26 is never exactly diametrically opposite to another such joint.

[0045] In each X-ray tube 3 there is an emitter assembly 19 for generating electron beams ES, which strike the anode arrangement 9 and thus generate the focal spot BF. The focal spot BF does not necessarily have an approximately punctiform shape. Rather, in a way that is known in principle, elongated focal spots BF can also be generated, for example, wherein the position of the focal spot BF is to be understood in each case as the position of its center point.

[0046] In the exemplary embodiment, the emitter assembly 19 comprises different cathodes 5, 25 in order to generate X-ray radiation of different doses and/or wavelengths. In any case, electrons are extracted from the cathode 5, 25 with the aid of an extraction grid 20, wherein the electron beam ES is deflectable in a defined manner with the aid of an electrode arrangement 21 which comprises multiple electrodes 22, 23. A plurality of cathodes 5, 25 are arranged together on a circuit board 24.

[0047] The entire anode arrangement 9 interacting with the emitter assembly 19 of an X-ray tube 3 extends at the circumference of the radiator-detector ring 10 over an angle α which is significantly less than 72°. An angle β, which indicates the extension of the X-ray detector 4 on the circumference of the radiator-detector ring, is significantly closer to 72°. In other words: the gaps formed between the individual X-ray detectors 4 on the circumference of the radiator-detector ring 10 are significantly narrower than the gaps formed between the radiator arrangements 18. A large number of possible focal spot positions extend within the X-ray tube 3 over an angle γ which is less than the angle α.

[0048] The electrode arrangement 21 is designed to selectively direct the electron beam ES onto the focal spot BF or onto a focal spot BF.sup.+, BF.sup.− that is offset in comparison thereto in the circumferential direction of the radiator-detector ring 10. With respect to the arrangement according to FIGS. 9 and 10, the focal spot BF is deflected clockwise in relation to the focal spot BF and the focal spot BF.sup.− is deflected counterclockwise. The deflections of the electron beam ES, which mean an offset of the focal spot BF, are also referred to as beam toggling and enable focal spots BF.sup.−, BF, BF.sup.+ to be placed particularly closely staggered on the circumference of the radiator-detector ring 10. A total number of several hundred focal spot positions, which corresponds to a multiple of the number of electron emitters 5, 25, is achievable.

LIST OF REFERENCE SIGNS

[0049] 1 computer tomograph [0050] 2 gantry [0051] 3 X-ray tube [0052] 4 X-ray detector [0053] 5 cathode of the first type, electron emitter [0054] 6 anode [0055] 7 movable frame [0056] 8 operating and evaluation unit [0057] 9 anode arrangement [0058] 10 radiator-detector ring [0059] 11 first fixed radiator-detector element [0060] 12 second fixed radiator-detector element [0061] 13 third fixed radiator-detector element [0062] 14 fourth fixed radiator-detector element [0063] 15 patient bed [0064] 16 sliding mechanism [0065] 17 fitting [0066] 18 radiator assembly [0067] 19 emitter assembly [0068] 20 extraction grid [0069] 21 electrode arrangement [0070] 22 electrode [0071] 23 electrode [0072] 24 circuit board [0073] 25 cathode of the second type, electron emitter [0074] 26 displaceable radiator-detector element [0075] α angle over which the anode arrangement of a radiator-detector element extends [0076] β angle over which the detector of a radiator-detector element extends [0077] γ angular range in which the possible focal spots of an anode arrangement are located [0078] BF focal spot (general) [0079] BF.sup.+, BF.sup.− focal spot, generated by means of an electron emitter (in the middle position and in two positions offset in the circumferential direction of the radiator-detector ring) [0080] ES electron beam [0081] MA central axis [0082] RS X-ray radiation