X-ray system

Abstract

X-ray system (2) comprising an X-ray source (4) which, during operation, generates X-ray radiation (10) at several X-ray focal spots (8), - wherein each X-ray focal spot (8) is assigned a collimator (12) which selects the X-ray radiation (10) generated in the respective X-ray focal spot (8) and directed towards a common detector (14), and - wherein the collimators (12) are arranged in a fixed position with respect to their respective associated X-ray focal spot (8).

Description

[0001] The invention relates to an X-ray system with an X-ray source which generates X-ray radiation at several X-ray focal spots during operation, wherein each X-ray focal spot is assigned a collimator.

[0002] X-ray systems are used in medical examinations. X-rays are generated in the focal spot of an X-ray source and emitted from there. The X-rays then penetrate the object being examined, with at least a portion being absorbed by the object. The X-rays then generate an X-ray image on a detector, particularly a digital one. If several X-ray images of the object (projections) are taken from different angles (projection angles), a suitable algorithm can be used to create a three-dimensional reconstruction of the object and generate image data from these projections. This method is advantageous for better distinguishing and localizing structures within the object, which, for example, might otherwise result in a relatively unclear X-ray image due to their relative positions in a single image.For example, in mammography using so-called tomosynthesis, a tumor is easier to distinguish from the tissue above or below it compared to a conventional two-dimensional mammogram of the breast, thus avoiding misdiagnoses.

[0003] In tomosynthesis, multiple projections of the object are acquired from different angles within a limited angular range, for example, between 10° and 50°. This is achieved by changing the relative orientation of the detector, the object, and an X-ray focal spot of the X-ray source. For example, both the detector and the X-ray source are moved relative to each other in a predefined manner. Alternatively, the detector is stationary and only the X-ray source is moved, or the X-ray source is stationary and only the detector is moved.

[0004] US patent 7,751,528 discloses another possibility, in which the X-ray system has a stationary detector and the X-ray source is not mechanically moved. Here, the X-ray source has several stationary X-ray focal spots, which are activated sequentially and emit X-rays. The X-ray focal spots are spatially distributed in such a way that suitable projections for reconstructing the object are generated. For example, the X-ray focal spots are arranged on a straight line parallel to the detector.

[0005] During the acquisition of the projections, the X-ray radiation emitted by each X-ray focal spot is collimated onto the detector using a collimator. In other words, the X-ray radiation that is not directed at the detector is blocked by the collimator. In this way, particularly in mammography, the patient is not exposed to X-ray radiation that is not used for imaging, thus reducing the patient's radiation exposure.

[0006] The time required for an examination should be as short as possible. This reduces motion blur of the person being examined when the projections are taken. Furthermore, in mammography, for example, an uncomfortable or painful examination for the person being examined is shortened.

[0007] For example, the X-ray source and / or the collimator used to capture the projections are adjusted during the examination, resulting in a comparatively long time being lost due to these adjustments. Consequently, the examination time is relatively long, leading to a comparatively high degree of motion blur and / or discomfort for the patient.

[0008] From WO 2014 / 116665 A2, a system suitable for tomosynthesis with multiple X-ray focal spots is known, in which the X-ray radiation emitted from an X-ray focal spot is collimated by means of a common collimator or by means of individual collimators. The X-ray source and / or the collimator(s) are arranged and designed to be adjustable, for example, rotatable or movable, so that the imaging geometry can be adapted to the intended examination. For this purpose, the X-ray source and the collimator(s) must be controlled accordingly, and the system must have an adjustment device suitable for this purpose.

[0009] The invention is based on the objective of providing a particularly suitable X-ray system in which the examination time is as short as possible and / or which has the simplest possible design.

[0010] With regard to the X-ray system, the problem is solved according to the invention by the features of claim 1. Advantageous embodiments and further developments are the subject of the dependent claims.

[0011] The X-ray system has an X-ray source which, during operation, generates X-rays at several X-ray focal spots. Each X-ray focal spot is assigned a collimator, which selects the radiation generated at that spot and directed onto a common detector. In other words, the X-rays emitted by the X-ray focal spots are collimated onto the detector common to all X-ray focal spots by means of their respective collimators. The collimators are fixed relative to their respective X-ray focal spots. In other words, the relative position between the X-ray focal spot and the collimator remains constant over time.

[0012] The X-rays emitted by one of the X-ray focal spots penetrate an object positioned between the X-ray source's focal spot and the detector at a projection angle determined, for example, by the orientation of the detector or, preferably, the object. The X-rays are detected by the detector. In this way, a projection image is acquired by the detector. For three-dimensional reconstruction, and thus for generating image data from the reconstruction, at least two different projections of an object are acquired, preferably a number of different projections corresponding to the number of X-ray focal spots. In other words, at least two X-ray images acquired at different projection angles are necessary for the reconstruction.

[0013] During operation of the X-ray system, X-rays are generated in the X-ray focal spots. These focal spots are spatially distributed within the X-ray source. Specifically, the focal spots are spaced apart from one another, meaning they do not partially or completely overlap. Preferably, the X-ray source locations are of the same size, and preferably, the focal spots are arranged regularly in a line or on a surface.

[0014] For example, the X-ray focal spots are equidistant along a straight line parallel to the detector. Alternatively, the X-ray focal spots are arranged along a segment of a circular arc, where the arc defines a plane perpendicular to the detector. In another alternative, the X-ray focal spots are arranged in a matrix, i.e., a grid-like pattern on a flat or substantially spherical surface. Due to this regular arrangement, three-dimensional reconstruction of the object is particularly simplified.

[0015] Due to the spatial distribution of the X-ray focal spots, projections of the object are recorded from different projection angles. In contrast to X-ray systems that only have a single X-ray focal spot, this method allows for recording projections from different angles without having to adjust the X-ray source and thus the X-ray focal spot, for example by moving or swiveling it.

[0016] The detector is designed to capture (detect) the X-rays emitted by the X-ray source; that is, the detector is sensitive to electromagnetic radiation in a wavelength range corresponding to the emitted X-rays. Specifically, the detector is a digital detector, for example, a flat-panel X-ray detector (solid-state detector) or a detector with a scintillator and a camera.

[0017] The X-ray source is controlled by a control unit, in particular such that the X-rays are emitted sequentially from the corresponding X-ray focal spots. For example, the detector is also controlled by the control unit in such a way that the recording of a projection by the detector occurs synchronously (simultaneously or time-correlated) with its exposure to the emitted X-rays.

[0018] The collimators are made of a material that absorbs X-rays as effectively as possible. For example, collimators are made of lead, tungsten, or brass. Furthermore, the collimators are shaped or geometrically designed such that the X-rays emitted by the X-ray focal spot associated with the collimator are collimated onto the detector. In other words, the collimator absorbs that portion of the X-rays emitted by the focal spot which would not reach the detector without considering the interaction of the X-rays with the object. The collimator is advantageously positioned between the associated focal spot and the detector. If the object under investigation is located between the focal spot and the detector, the collimator is positioned between the focal spot and the object.

[0019] For example, the collimators can be designed as a single, continuous piece or in one part. Preferably, however, the collimators are each designed as a separate part. Compared to the continuous design, this method particularly allows for individual adjustment of each collimator during assembly.

[0020] Due to the fixed arrangement of the collimators with respect to the respective X-ray focal spot, and provided that the detector is fixed with respect to the X-ray focal spots, it is possible for each collimator to have only one continuous recess from its side facing the X-ray focal spot to its side facing the detector, which is penetrated unhindered by the X-ray radiation during operation of the X-ray system.

[0021] In particular, the detector has a rectangular detector area, so the recess is expediently shaped like a truncated pyramid. The collimator thus has no apertures or other adjustable elements, which is why, advantageously, no control system for the collimators is necessary. In summary, a particularly simple collimator design has been achieved.

[0022] Due to the collimation of the X-rays onto the detector, the object, such as a body part of the person being examined (patient), is only exposed to the portion of the X-rays emitted by the X-ray focal spots that contributes to the recording of a projection by the detector. Thus, the radiation exposure of the person being examined is particularly low. Furthermore, the fixed arrangement of the collimators relative to their respective X-ray focal spots makes the examination time for recording the projections comparatively short.

[0023] The invention is based on the following consideration: in an X-ray system with only one focal spot, both the X-ray source and the collimator would have to be adjusted when examining the object to capture projections at different projection angles. In X-ray systems with multiple focal spots, it is not necessary to adjust the X-ray source to capture the projections. However, if the collimators are not fixed relative to their respective focal spots, and / or if each focal spot does not have its own collimator, the collimators are adjusted to collimate the X-rays emitted by each focal spot onto the detector during the examination.This adjustment is comparatively time-consuming, with the adjustment time being particularly long compared to the detector readout time. Consequently, the time between capturing two projections with different projection angles is essentially determined by the adjustment time. If the collimators are fixed, however, this comparatively long adjustment time is eliminated, thus advantageously reducing the examination time.

[0024] The X-ray source is conveniently located in an X-ray tube housing. The X-ray tube housing covers the X-ray source as well as, for example, the electronics of the X-ray system.

[0025] In a practical embodiment, the X-ray source is designed as an X-ray tube with an anode and a number of cathodes. In other words, the anode and the cathodes are enclosed in a common vacuum shell, forming the X-ray tube. In a practical embodiment, the number of cathodes corresponds to the number of X-ray focal spots, so that each anode produces one X-ray focal spot. An X-ray focal spot is thus understood to be the area of ​​the anode in which electrons emitted from the corresponding cathode interact with the anode, thereby generating X-ray radiation. Alternatively, the X-ray tube has several anodes, each of which, for example, has one X-ray focal spot, or alternatively, each has several X-ray focal spots.

[0026] In an alternative configuration, the X-ray source has several X-ray tubes. For example, one X-ray tube has an anode with one X-ray focal spot, or alternatively, an anode with several X-ray focal spots, or several anodes, each with one X-ray focal spot, or several anodes with several X-ray focal spots.

[0027] At most, the X-ray focal spots for recording the projections with different projection angles are arranged in a suitable spatial distribution.

[0028] To enable a fixed arrangement of the respective collimators relative to the X-ray focal spots, and thus a comparatively simple collimator design (e.g., without adjustable elements), the detector must be fixed in position relative to the X-ray focal spots. Additionally, the collimator of each associated X-ray focal spot must always be positioned outside the area of ​​space penetrated by the X-rays from the other focal spots collimated onto the detector, without requiring any adjustment. This is possible with a relatively close arrangement of the collimators to the corresponding X-ray focal spots. This results in a maximum distance between the collimator and the line or surface on which the X-ray focal spots are located, within which a fixed arrangement of the collimator relative to the associated X-ray source point is possible.This depends in particular on the distance of the X-ray focal spot to a neighboring X-ray focal spot, on the width of the detector, and on the distance of the detector to the line or surface on which the X-ray focal points are arranged.

[0029] In summary, the collimators must be arranged such that they are positioned at a distance from the line or surface that is less than the maximum distance required to ensure a fixed arrangement with respect to the X-ray focal spots. In particular, due to this maximum distance, the collimators are preferably arranged within the X-ray tube housing.

[0030] In an advantageous embodiment, the collimators are arranged inside the X-ray tube. Consequently, the collimators are positioned sufficiently close to their respective X-ray focal spots; that is, the collimators are located at a distance from the line or surface on which the X-ray focal spots are arranged less than the maximum distance. Therefore, the collimators are advantageously fixed with respect to their respective X-ray focal spots.

[0031] Preferably, each collimator is connected to a support element. This support element can be adjusted, for example, during an assembly process before commissioning. This allows for a comparatively simple adjustment of the collimators.

[0032] Alternatively, the collimators are arranged outside the X-ray tube, or outside the X-ray tubes if the X-ray source has more than one X-ray tube. In this case, however, the collimators are not positioned further than the respective maximum distance from the line or area containing the corresponding X-ray focal spots. For example, the collimators are attached to a support element, adjustable for alignment in a single assembly step, analogous to the arrangement inside the X-ray tube.

[0033] In a practical further development, the collimators are arranged at the anode. In a version of the X-ray source with multiple anodes, the collimators are arranged accordingly at the anodes. Consequently, the collimators have a comparatively small distance to their respective X-ray focal spot, so that the collimators are advantageously arranged in a fixed position.

[0034] In particular, the collimators are attached to the anode using an additive manufacturing process. For example, the collimators are printed onto the designated locations using a 3D printing process. Alternatively, the collimators are manufactured by milling or turning prior to their assembly and then attached to their designated locations on the anode, for example by soldering, welding, snapping on, or bonding.

[0035] In an alternative embodiment, the collimators are an integral part of the vacuum envelope. In this configuration, the collimators each include, for example, a window in the vacuum envelope that is transparent to X-rays, through which the X-rays from the X-ray tube exit. Alternatively, the window is attached to the end of the collimators.

[0036] Alternatively, the collimators are attached to the vacuum shell of the X-ray tube either on the inside or outside, for example by gluing, so that the X-ray radiation penetrates the window of the vacuum shell in its direction of radiation towards or in front of the collimator.

[0037] According to an advantageous embodiment, an X-ray system configured according to one of the variants described above is used to generate image data during tomosynthesis, particularly in mammography. Due to its fixed collimators, this X-ray system has a comparatively simple design. Furthermore, the examination time of an object, particularly a patient's breast in the case of mammography, is advantageously relatively short using this X-ray system, thus reducing motion blur caused by the patient and / or shortening an uncomfortable or painful examination for the patient.

[0038] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

[0039] Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. The drawing shows: Fig. 1 schematically an X-ray system with an X-ray source with several X-ray tubes, each with an X-ray focal spot, from which X-ray radiation is emitted collimated onto a detector by means of a collimator, wherein the X-ray radiation penetrates an object at a projection angle, Fig. 2 schematically the X-ray source according to Fig. 1 in an alternative embodiment, wherein the X-ray source is designed as an X-ray tube with an arc-shaped anode having all X-ray focal spots, and wherein the collimators are designed as interconnected units and arranged inside the X-ray tube, Fig. 3 schematically an alternative design of the X-ray tube according to Fig. 2 in a cross-section through an X-ray focal spot, with a cathode and with a collimator as well as with the anode, wherein the collimator is connected to the anode, Fig. 4 an alternative design of the X-ray tube according to Fig. 3, wherein the collimator is designed as a component of a vacuum shell of the X-ray tube.

[0040] Corresponding parts are marked with the same reference symbols in all figures.

[0041] In Fig. Figure 1 shows an X-ray system 2 with an X-ray source 4, which has several X-ray tubes 6, whereby for the purpose of improved clarity only four X-ray tubes 6 are shown as an example. The X-ray tubes 6 are activated sequentially, i.e., one after the other in time, by means of a control unit not shown, so that X-ray radiation 10 is emitted from each X-ray focal spot 8 arranged in the X-ray tube. Fig. 3 and Fig. 4) is sent out.

[0042] The X-ray radiation 10 emitted from an X-ray focal spot 8 is focused by means of a collimator 12 onto a detector 14 with a detector width D B collimated, which is fixedly arranged with respect to the X-ray focal spots 8. In other words, the X-ray radiation 10 that is not directed towards the detector is blocked by means of the collimator 12 assigned to the corresponding X-ray focal spot 8.

[0043] The X-ray radiation 10 directed towards the detector 14 is collectively represented as beam 15. In summary, the collimators 12 select the X-ray radiation 10 emitted from their respective associated X-ray focal spot 8 that is directed towards the detector 14. Consequently, the portion of the X-ray radiation 10 that does not contribute to the projection of an object 16 is absorbed by the respective associated collimator 12.

[0044] Using the X-ray system 2, several projections are created at a projection angle α. These projections are used for the three-dimensional reconstruction of object 16 and for obtaining image data from this reconstruction by means of an evaluation unit (not shown). The projection angle α is determined here by the position of the respective X-ray focal spot 8 relative to object 16. For the sake of clarity, only one projection angle α corresponding to an X-ray focal spot 8 is shown.

[0045] As in the Fig. As shown in Figure 1, the detector 14 and the X-ray source 4 are fixed in place, thus limiting the range of possible projection angles α. A three-dimensional reconstruction of an object 16 using projections acquired from a limited angular range is referred to as tomosynthesis. In summary, the X-ray system 2 is used in tomosynthesis, particularly in mammography, to generate image data from a three-dimensional reconstruction of the object 16.

[0046] The X-ray focal spots 8 are arranged equidistantly on a straight line L parallel to and spaced apart from the detector 14, which is a suitable arrangement for reconstruction. Each X-ray focal spot 8 has a distance D from its neighboring X-ray focal spot 8. Q , and the line L has a distance D to detector 14.

[0047] Advantageously, the collimators 12 are arranged in a fixed position relative to their respective associated X-ray focal spots 8. In other words, the collimators 12 are neither adjustable nor movable. The collimators have a maximum distance M from the line L. In other words, each collimator 12 is arranged in an area that is not penetrated by the collimated beams 15 from the other X-ray focal spots 8. In this way, the collimators 12 are arranged in a fixed position relative to their respective associated X-ray focal spots 8 without restricting the beam 15 collimated onto the detector 14 from the other X-ray focal spots 8. The following applies to the maximum distance M: M = D * D Q / (D B +D Q ).

[0048] Due to the fixed arrangement of the collimators 12, the collimators 12 and the X-ray system 2 have a simple design. Each collimator 12 has only one recess 18, which extends continuously from the side of the respective collimator 12 facing the associated X-ray focal spot 8 to the side of the respective collimator 12 facing the detector 14. Thus, the collimators 12 have no adjustable elements such as adjustable apertures.

[0049] In summary, the collimators 12 are neither adjustable nor do they have adjustable elements, so neither an adjustment device for the collimators 12 or for adjustable elements nor a corresponding control system is necessary. Furthermore, this eliminates the time required for adjustment, thus reducing the overall duration of the tomosynthesis.

[0050] In the Fig. The collimators 14 are arranged outside the corresponding X-ray tube 6, but not further than the maximum distance M from the line L. The X-ray source 4, and thus the X-ray tubes 6, are arranged in a common X-ray tube housing 20. The X-ray tube housing 20 also includes other elements not shown, such as electronics.

[0051] Fig. Figure 2 shows an alternative embodiment of the X-ray source 4. This has a single X-ray tube 6 with an anode 22, on which, during operation, sequential X-rays are emitted by means of an associated cathode 24 ( Fig. 3 and Fig. 4) the X-ray focal spots 8 are generated. The line L on which the X-ray focal spots 8 are arranged is arc-shaped. Furthermore, the collimators 12 are arranged inside the X-ray tube 6, and the collimators 12 are formed as a single unit. In other words, the collimators 12 are formed as a single element with a number of recesses 18 corresponding to the number of X-ray focal spots 8. The collimators 12 are fixed relative to the anode 22. The collimators 12 are connected to a support element (not shown). This support element allows for adjustment of the collimators 12 during the assembly of the X-ray system 2 before its commissioning.

[0052] In Fig. 3 is an alternative design of the X-ray tube 6 according to the Fig. Figure 2 shows a cross-section through an X-ray focal spot 8, with the view along line L. Only the cathode 24 and the collimator 12, both arranged in the plane of the section, are shown. However, the X-ray tube 6 contains a number of cathodes 24 corresponding to the number of X-ray focal spots 8. Each cathode 24 generates one X-ray focal spot 8.

[0053] For this purpose, electrons 26 emitted from the cathode 24 are ejected due to a high voltage U applied between the cathode 24 and the anode 22. H The X-rays are accelerated towards the anode 22. They then interact with the anode 22 in the X-ray focal spot 8 of the anode 22, generating X-ray radiation 10. The beam 15 of collimated X-ray radiation 10 penetrates through a window 28 in the vacuum shell 30 surrounding the X-ray tube 6, which is transparent to X-ray radiation 10, to the outside of the X-ray tube 6.

[0054] In contrast to the execution according to Fig. 2 The collimator 12 is integrated into the anode 22. In particular, the collimator 12 is attached to the anode 22 by means of an additive manufacturing process, for example by means of a 3D printing process. In this way, the collimators 12 are fixedly arranged with respect to their respective associated X-ray focal spot 8.

[0055] Fig. Figure 4 shows an alternative cross-sectional design of the X-ray tube 6. Analogous to the Fig.Figure 3 shows the X-ray tube with the anode 22 and the cathodes 24 for generating the X-ray radiation 10 in the corresponding X-ray focal spots 8. However, this illustration only shows the cathode 24 and the collimator 12, both arranged in the plane of section. The collimator 12 is a component of the vacuum envelope 30 of the X-ray tube 6, so that the collimator 12 is fixed relative to its associated X-ray focal spot 8. The window 28 of the vacuum envelope 30 of the X-ray tube 6 is located on the inside of the tube at the collimator 12.

[0056] The invention is not limited to the embodiments described above. Rather, other variants of the invention can also be derived by those skilled in the art without departing from the subject matter of the invention. In particular, all individual features described in connection with the embodiments can also be combined with one another in other ways without departing from the subject matter of the invention. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 7,751,528

[0004] WO 2014 / 116665 A2

[0008]

Claims

[1] X-ray system (2) comprising an X-ray source (4) which, during operation, generates X-ray radiation (10) at several X-ray focal spots (8), - wherein each X-ray focal spot (8) is assigned a collimator (12) which selects the X-ray radiation (10) generated in the respective X-ray focal spot (8) and directed towards a common detector (14), and - wherein the collimators (12) are arranged in a fixed position with respect to their respective associated X-ray focal spot (8). [2] X-ray system (2) according to claim 1, characterized by , that the X-ray source (4) is designed as an X-ray tube (6) with an anode (22) having the X-ray focal spots (8) and with a number of cathodes (24). [3] X-ray system (2) according to claim 2, characterized by , that the number of cathodes (24) corresponds to the number of X-ray focal spots (8). [4] X-ray system (2) according to claim 2 or 3, characterized bythat the collimators (12) are arranged in the X-ray tube (6). [5] X-ray system (2) according to any one of claims 2 to 4, characterized by , that the collimators (12) are arranged at the anode (22). [6] X-ray system (2) according to claim 2 or 3, characterized by , that each of the collimators (12) is a component of a vacuum shell (30) of the X-ray tube (6). [7] X-ray system (2) according to any one of the preceding claims, characterized by , that each collimator (12) has only one continuous recess from its side facing the X-ray focal spot (8) to its side facing the detector (14), which is penetrated unhindered by the X-ray radiation (10) during the operation of the X-ray system (2). [8] X-ray system (2) according to claim 7, characterized by that the recess is shaped like a truncated pyramid. [9] X-ray system (2) according to any one of the preceding claims, characterized by, that each X-ray focal spot (8) is assigned an X-ray tube (6) and a collimator (12) arranged within an X-ray tube housing (20). [10] Use of an X-ray system (2) according to any one of claims 1 to 9 for generating image data in tomosynthesis.

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