COMPUTED TOMOGRAPHY SYSTEM, DETECTOR RING, AND METHOD FOR ADJUSTING THE APERTURE APERTURE OF A COMPUTED TOMOGRAPHY SYSTEM - Patent application

Abstract

To provide a detection ring for a computed tomography system and an adjusting method for a diaphragm aperture of a computed tomography system.SOLUTION: A computed tomography system includes an examination area 2 and a static gantry 4 equipped with a detector ring 6 and an X-ray source ring 8 that surround the examination area respectively and have a substantially common axial direction. The X-ray source ring has a diameter larger than that of the detector ring. When viewed in a radial direction, the X-ray source sing is arranged on the further outside of the detector ring around the examination area. The detector ring is arranged deviated in the axial direction with respect to the X-ray source ring so that a beam outlet aperture 9 of the X-ray source ring is not covered with the detector ring at least partially when viewed in the radial direction with respect to the examination area.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a computed tomography system, a detector ring for a computed tomography system, and a method for adjusting the aperture of a computed tomography system. [Background technology]

[0002] A typical computed tomography (CT) system typically includes an X-ray tube and a detector facing the X-ray tube. To image the patient, the X-ray tube and detector rotate around the patient. This rotation allows for the acquisition of a three-dimensional image of the patient. However, rotation also has drawbacks. Rotation places relatively high requirements on mechanics and data transmission. These increased requirements result in increased manufacturing and maintenance efforts, generally increased costs, and potentially compromise image quality. For example, rotation generates vibrations that can cause interference frequencies in measurement signals and thus artifacts in CT images. Rotation in general, and accidental vibrations caused by rotation in particular, can lead to faster wear of components. Furthermore, rotation requires that components be manufactured particularly robustly, as deformation of components can significantly affect image quality. This increases space requirements and hardware costs. For example, rotation can make data transmission via sliding contacts difficult, potentially limiting data transmission capacity. Summary of the Invention [Problem to be solved by the invention]

[0003] The object of the present invention is therefore to provide a possibility by which the above-mentioned drawbacks can be addressed and at least partially ameliorated. [Means for solving the problem]

[0004] This problem is solved by a computer tomography system according to claim 1, a detector ring according to claim 13 and a method according to claim 15. Further features and advantages emerge from the dependent claims, the description and the accompanying drawings.

[0005] According to a first aspect of the present invention, there is provided a computed tomography system comprising an examination region and a static gantry. The static gantry comprises a detector ring and an X-ray source ring, each of which surrounds the examination region and has a substantially common axial direction. The X-ray source ring has a larger diameter than the detector ring, such that the X-ray source ring is positioned further outward around the examination region than the detector ring when viewed in a radial direction. The detector ring is positioned axially offset relative to the X-ray source ring such that a beam exit aperture of the X-ray source ring is at least partially unobstructed by the detector ring when viewed in a radial direction relative to the examination region.

[0006] The examination area is an area in which a subject or object can be examined, in particular by computed tomography measurements carried out by a computed tomography system, and a computed tomography (CT) image of the subject or object can be taken. The subject or object can be, for example, a human being, an animal, or an organ or body region, for example a body part such as the chest region or the head region, or another object (for example baggage or a piece of material whose properties are to be examined).

[0007] A gantry with a detector ring and an X-ray source ring is arranged around the examination region. The gantry can be a particularly short annular tunnel. The axial direction of the annular tunnel can approximately correspond to the axial direction of the detector ring and the X-ray source ring. The axial direction can also be referred to as the z-direction. In this context, the term "approximately" should be understood to mean that there may be some deviations, for example due to the structure. However, it is preferable that the axial directions of the mentioned components, particularly the detector ring and the X-ray source ring, do not differ from each other by more than 10°. In this context, the radial direction should be understood as a direction perpendicular to the axial direction, particularly extending radially outward from the center point of each ring. Therefore, the term radial direction should be understood so that there are multiple directions corresponding to one radial direction, i.e., according to the totality of possible radial extension directions. The radial direction can also be referred to as the x-direction, the y-direction, and / or the x,y direction.

[0008] The gantry is static. This should be understood to mean that, in particular in contrast to other common gantries, the gantry does not rotate during the CT measurement. This is made possible by the presence of a detector ring and an X-ray source ring. In this way, a complete image can be generated without rotating the detector and the X-ray source. In particular, the detector ring can be a 360° detector. A 360° detector is a detector that can receive signals emanating from the examination region in all radial directions without the need to rotate itself. In particular, the detector ring can be a static detector ring. In particular, the X-ray source ring can be a 360° X-ray emitter. A 360° X-ray emitter is an X-ray emitter that can transmit X-rays to the examination region from an entire 360° area around the examination region without the need to rotate itself. In particular, the X-ray source ring can be a static X-ray source ring. The detector ring can, for example, have multiple detector elements distributed around the detector ring. The X-ray source ring can, for example, have multiple X-ray sources distributed around the X-ray source ring. The X-ray source can preferably be based on nanotube field emission technology. X-ray sources based on field emission have the advantage of avoiding afterglow effects as much as possible compared to X-ray sources based on thermally induced emission, which are typically used in prior-art CT systems, thereby enabling faster switching. However, other X-ray sources can also generally be used. For this reason, the X-ray source ring can be configured to sequentially activate individual or multiple X-ray sources during a CT scan of a subject or subjects in the examination region. As a result, the advantages of rotation can be "simulated," so to speak, according to CT systems customary in the prior art. Advantageously, actual rotation of the gantry can be avoided, thereby largely avoiding the aforementioned disadvantages of rotating components. Therefore, typically complex and expensive interfaces between parts that move relative to each other, such as sliding contacts, are not required. Rotation-induced vibrations and the resulting artifacts and wear in the measurement data can also be avoided. Furthermore, fewer stable components are required, allowing for a more compact design.For example, the detector or detector ring module carrier and detector mechanism can be constructed in a significantly simpler, lighter, and more cost-effective manner, since the detector does not need to withstand any rotational forces. For example, the system according to the present invention can be constructed for mobile applications. Furthermore, not having to consider inertia during mechanical rotation advantageously allows for faster image capture and greater flexibility in selecting successive capture angles.

[0009] The X-ray source ring has a larger diameter than the detector ring. As a result, the X-ray source ring is positioned further outward around the examination region than the detector ring in the radial direction. In other words, the X-ray source ring is positioned further outward in the gantry than the detector ring. This advantageously allows the X-ray source ring and the detector ring to be configured in a particularly space-efficient manner. At the same time, the detector ring is axially offset from the X-ray source ring, so that the beam exit opening of the X-ray source ring is at least partially, i.e., not completely, covered by the detector ring when viewed radially relative to the examination region. In particular, it is possible to ensure that the center of the beam exit opening is not covered by the detector ring. The beam exit opening is understood to be wide. This generally refers to the position on the X-ray source ring from which X-rays are emitted outward from the X-ray source. In many cases, for example for collimation purposes, particularly in some embodiments described herein, it may be advantageous to partially limit the beam exit, especially at the beam edge, by a portion of the detector ring or a portion on the detector ring in a predetermined manner. The detector ring may optionally function as a collimator or part of a collimator for the beam exit aperture and may therefore cover part of the beam exit aperture, however at least part of the beam exit aperture, preferably the centre, is generally left unobstructed.

[0010] According to a preferred embodiment, the detector ring and the X-ray source ring overlap in the axial direction. This variant allows for a particularly compact design of the gantry. Furthermore, this allows the detector ring and the X-ray source ring to be assembled in a particularly compact axial manner, which results in improved image quality. In particular, the distance from the focal point of the X-ray source and the detector center of the X-ray source ring can be reduced. This results in fewer image errors due to, for example, axial misalignment, or in correspondingly easier image correction.

[0011] According to one embodiment, the detector ring and the X-ray source ring are attached to the gantry from different axial sides. For example, the detector ring can be attached to the gantry in the positive axial direction (or +z direction), and the X-ray source ring can be attached to the gantry in the negative axial direction (or z direction). Assembly from different sides allows for particularly good spatial division, on the one hand, and particularly good accessibility of the two components, i.e., the X-ray source ring and the detector ring, individually, on the other hand. This can be advantageous, for example, for maintenance purposes. For example, the detector ring can be removable or partially removable without significantly complicating the removal of the X-ray source ring. Thus, for example, the detector ring can be directly accessible and removable, requiring, for example, the removal of only one cover plate.

[0012] According to one embodiment, the gantry comprises an annular aperture having at least a first aperture portion and a second aperture portion, the aperture being positioned or positionable in front of the beam exit aperture of the X-ray source ring, the first aperture portion being fixed to the detector ring or being an integral part of the detector ring. In particular, the aperture can be positioned in front of the beam exit aperture so as to collimate the X-rays of the X-ray source ring. By fixing the aperture to the detector ring, the detector ring can be positioned particularly close to the beam exit aperture, achieving an even more compact design. The second aperture can preferably be attached to the X-ray source ring or another part of the gantry, respectively, or be an integral part thereof. The aperture can be a ring that is completely closed in the circumferential direction of the X-ray source ring or the detector ring. The first aperture portion and the second aperture portion can together form a channel that restricts the propagation of X-ray radiation. The channel can extend in particular in the radial direction. The channel can have an approximately constant cross section and / or a constant channel opening relative to the beam exit aperture in the circumferential direction.

[0013] According to one embodiment, the detector ring is configured to be displaceable together with the first aperture section, and the aperture opening can be adjusted by axially displacing the detector ring. This embodiment is an efficient way to realize various aperture openings for the X-ray source. In particular, it can enable particularly space-saving adjustable apertures. Advantageously, therefore, the position of the detector ring and the beam distribution can be adapted simultaneously. In this way, a simple and effective synchronization of the X-ray propagation and the detector position is possible.

[0014] According to one embodiment, the computed tomography system further comprises a patient couch, and the detector ring is attached to the gantry in an axial direction from the side of the patient couch. The patient couch can preferably be moved axially in and out of the gantry. Particularly easy access to the detector ring, for example for maintenance purposes, is made possible by attaching the detector ring according to this embodiment. The detector ring or each element of the detector ring can be particularly easily removed from the gantry.

[0015] According to one embodiment, the detector ring comprises functional units with detector elements that can be individually removed from the gantry. Individually removable functional units are advantageous, for example, because they allow for maintenance or replacement of individual detector elements without removing the entire detector ring. Thus, for example, it is easier to maintain the overall orientation and alignment of the detector ring, so that only individual functional units need to be reinstalled, while the overall orientation of the detector ring (and possibly the aperture) remains unchanged. This simplifies maintenance and can be more cost-effective. The detector ring can include additional functional units as needed. Individual functional units can comprise or be modules, cables, and / or DSFs (data streaming front ends). For example, a functional unit can be a module with a partially circular array of detector elements.

[0016] According to one embodiment, the detector ring includes at least one housing piece configured to allow at least one of the functional units to be at least partially inserted into the housing piece. At least one functional unit can be inserted into the housing piece. For example, at least one functional unit can be inserted into the housing piece while the detector ring is in operation. The functional unit can be removed or made removable from the housing for maintenance. The housing piece can preferably be annular or partially annular. The housing piece can be configured to allow, in particular, detector elements of at least one functional unit to be inserted into the housing piece. Advantageously, the detector elements can thus have positions defined by the positions of the housing pieces. In this way, the detector elements can be replaced without the need for subsequent readjustment of their positions, or adjusting the positions of the detector elements is simplified. Multiple functional units with detector elements can be inserted into the housing piece. For example, one housing piece can be configured so that, in each case, two functional units can be at least partially inserted into the housing piece. In either case, the possibility of installing two functional units is particularly advantageous, as it allows both stable positioning and easy maintenance. The first throttling part described herein can preferably be fixed to the housing piece, which is advantageous because it prevents fluctuations in the position of the first throttling part during removal or replacement of the functional units.

[0017] According to one embodiment, the detector ring comprises a plurality of housing pieces that, when assembled, define the annular shape of the detector ring. In this sense, the housing pieces can be segments of the detector ring, in particular circular segments. The housing pieces can be circular segments of approximately the same size as the detector ring. The detector ring can preferably comprise three or more housing parts. Particularly preferably, the detector ring can comprise three housing parts. The three housing pieces can in particular be three substantially equal-sized circular segments of the detector ring. For example, each housing piece can be a 120° segment. The division into three housing pieces has proven to be particularly advantageous for maintenance purposes and flexible adjustment of the orientation of the detector ring. The first throttle piece described herein can comprise or be assembled from a plurality of first throttle pieces, each of which is fixed to one of the housing pieces.

[0018] According to one embodiment, at least one of the functional units comprises a guide, which allows the functional unit to be inserted into the housing piece with precision in terms of positioning. Alternatively or additionally, the guide is provided as part of the housing piece. The guide can be, for example, a guide rail or a guide rod. The housing piece can, for example, comprise an inner edge or a guide tunnel configured to interact with the guide of the functional unit. The guide can be used to allow particularly precise positioning of the functional unit in the housing piece. Furthermore, the guide can contribute to preventing damage to the functional unit, in particular the detector element, due to, for example, impacts during use.

[0019] According to one embodiment, the detector ring and / or the housing pieces comprise a scattered beam collimator oriented to shield the detector elements of the detector ring from the scattered beam of the X-ray source ring, and the housing pieces are configured such that when at least one functional unit is inserted into the housing pieces, the detector elements of the at least one functional unit are inserted with an exact fit relative to the scattered beam collimator, thus advantageously allowing the positioning of the scattered beam collimator to be maintained, for example while exchanging functional units.

[0020] According to one embodiment, the X-ray source ring comprises a plurality of X-ray source segments. All advantages and features relating to the maintenance of the detector ring can be transferred to the X-ray source ring as well. Therefore, individual segments of the X-ray source ring can be advantageously removed. For example, corresponding functional units and / or housing pieces of the X-ray source ring can also be provided.

[0021] A further aspect of the present invention is directed to a detector ring for a computed tomography system, the detector ring comprising at least one annular or partially annular housing piece and one or more functional units having detector elements, the housing piece configured to allow at least one functional unit to be at least partially inserted into the housing piece. The detector ring may be a detector ring as described herein, particularly with respect to a computed tomography system. All advantages and features of the computed tomography system may be similarly transferred to the detector ring, and vice versa. The detector ring may comprise multiple housing pieces as described herein, which, when assembled, define the annular shape of the detector ring.

[0022] According to one embodiment, at least one of the functional units comprises a guide oriented to allow the functional unit to be inserted into the housing piece in a positionally accurate manner. Alternatively or additionally, the guide is used as part of the housing piece. The guide can be, for example, a guide rail or a guide rod. The housing piece can comprise, for example, an inner edge or a guide tunnel configured to interact with the guide of the functional unit.

[0023] According to one embodiment, the detector ring comprises a first aperture portion fixed to or part of the detector ring, which first aperture portion is configured to form, together with a second aperture portion, an aperture for an X-ray emission ring having a diameter larger than that of the detector ring. In particular, the aperture is provided for an X-ray ring as described herein. The first aperture portion can be fixed to, for example, a housing piece.

[0024] According to one embodiment, the detector ring and / or the housing piece comprises a scattered beam collimator, and the housing piece is adapted to be inserted such that when the at least one functional unit is inserted into the housing section, the detector elements of the at least one functional unit fit precisely relative to the scattered beam collimator.

[0025] A further aspect of the present invention is a method for adjusting an aperture of a computed tomography system having a static gantry, wherein the gantry comprises a detector ring, an X-ray source ring having a beam exit aperture, and an annular aperture having at least a first aperture portion and a second aperture portion, the aperture being positioned in front of the beam exit aperture of the X-ray source ring, and the first aperture portion being fixed to or an integral part of the detector ring. The computed tomography system may in particular be a computed tomography system as described herein. The method comprises the following steps: - By displacing the detector ring and thus the first aperture part in the axial direction, the spacing between the first aperture part and the second aperture part is changed and adjusted. The process includes:

[0026] All advantages and features of the computed tomography system and detector ring are applicable to this method and vice versa.

[0027] All embodiments described herein can be combined with each other unless otherwise stated. [Brief explanation of the drawings]

[0028] Hereinafter, embodiments will be described with reference to the accompanying drawings.

[0029] [Figure 1] 1 shows a schematic cross-sectional side view of a computed tomography system according to an embodiment of the present invention; [Figure 2] 1 shows a perspective view of a gantry of a computed tomography system according to an embodiment of the present invention; [Figure 3] 1 shows a housing piece and two functional units of a detector ring according to one embodiment of the present invention. [Figure 4] FIG. 1 shows a schematic illustration for adjusting an aperture of a computed tomography system having a static gantry according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] FIG. 1 shows a schematic cross-sectional side view of a computed tomography system according to an embodiment of the present invention. The computed tomography system includes a static gantry 4 arranged as a short, circular tunnel around an examination region 2. The gantry 4 includes a detector ring 6 and an X-ray source ring 8, one upper and one lower of which are shown, each surrounding the examination region 2. The detector ring 6 and the X-ray source ring 8 share a common axial direction, which corresponds to the z direction shown. The detector ring 6 is attached to the gantry 4 from the right side of the figure, and the X-ray source ring 8 is attached to the gantry 4 from the left side. This means that the detector ring 6 and the X-ray source ring 8 are attached to the gantry 4 from different sides. In this case, the detector ring 6 is attached to the gantry 4 from the side where the patient couch 3 is also located. The detector ring 6 and the X-ray source ring 8 partially overlap in the axial direction, i.e., part of the X-ray source ring 8 is at the same z position as part of the detector ring 6. The X-ray source ring 8 has a larger diameter than the detector ring 6, so that the X-ray source ring 8 is arranged further outward around the periphery of the examination region 2 than the detector ring 6 in the radial direction, i.e., in the x- and y-directions. Furthermore, the detector ring 6 is arranged axially offset relative to the X-ray source ring 8, so that the beam exit opening 9 of the X-ray source ring 8 is not completely covered by the detector ring 6 in the radial direction relative to the examination region 2. A first diaphragm section 11, which is part of an annular diaphragm 10 arranged in front of the beam exit opening 9, is fixed to the detector ring 6. A second diaphragm section 12 of the diaphragm 10 is attached to the X-ray source ring 8 itself. In this embodiment, and preferably also in other embodiments, the diaphragm sections 11 and 12 are particularly separate components but functionally interact with each other. The detector ring 6 is configured to be displaceable axially (i.e., in the z-direction) together with the first diaphragm section 11, so that the aperture of the diaphragm 10 can be adjusted by displacing the detector ring 6 in the axial direction.

[0031] FIG. 2 shows a perspective view of a gantry 4 of a computed tomography system according to one embodiment of the present invention. In this case, the gantry 4 is shown without an outer cover. A detector ring 6 is attached to the gantry 4. An X-ray source ring 8 (not shown here) is provided on the opposite side (rear side from this perspective) of the gantry 4. The detector ring 6 comprises three partially annular housing pieces 61 and, for each housing piece 61, two functional units 62 each having a detector element 63 inserted into the housing piece 61. The housing pieces 61 together provide the annular shape of the detector ring 6. Each functional unit 62 can be individually removed from the gantry 4. The X-ray source ring 8, not shown here, can optionally include multiple X-ray source pieces, as well as the functional units 62 or housing pieces 61 of the detector ring 6.

[0032] 3 shows a housing piece 61 and two functional units 62 of a detector ring 6 according to one embodiment of the present invention. The detector elements 63 of the two functional units 62 can be inserted into the housing piece 61. The functional units 62 each have a guide 64 in the form of a guide rod, which guides the functional units 62 along the inner edge of the housing piece 61 and thus orients the respective functional units 62 so that they can be inserted into the housing piece 61 with precision regarding positioning. The housing piece 61 further comprises a scattered beam collimator 65 oriented to shield the detector elements 63 from the scattered beam of the X-ray source ring 8. The guide 64 further ensures that the detector elements 63 are inserted with a precise fit relative to the scattered beam collimator 65 when the functional units 62 are inserted into the housing piece 61.

[0033] 4 shows a schematic diagram of a method for adjusting the aperture of a computed tomography system having a static gantry 4 according to one embodiment of the present invention. The gantry 4 comprises a detector ring 6, an X-ray source ring 8 having a beam exit aperture 9, and an annular aperture 10 having a first aperture portion 11 and a second aperture portion 12 arranged in front of the beam exit aperture 9 of the X-ray source ring 8. The first aperture portion 11 is fixed to the detector ring 6. As shown here, in this method, the detector ring 6, and therefore the first aperture portion 11, is displaced in the axial direction (z direction), so that the distance between the first aperture portion 11 and the second aperture portion 12 is changed (in this case, enlarged), and the aperture of the aperture 10 is adjusted.

Claims

1. an inspection area (2); a static gantry (4) including a detector ring (6) and an X-ray source ring (8), each of which surrounds the examination region (2) and has a substantially common axial direction; Equipped with the X-ray source ring (8) has a diameter larger than the detector ring (6), such that the X-ray source ring (8) is positioned further outwardly around the periphery of the examination region (2) than the detector ring (6) in the radial direction; the detector ring (6) is arranged axially offset relative to the X-ray source ring (8) so that a beam exit opening (9) of the X-ray source ring (8) is at least partially not covered by the detector ring (6) in a radial direction relative to the examination region (2); the gantry (4) comprises an annular iris (10) having at least a first iris portion (11) and a second iris portion (12); the aperture (10) is arranged in front of the beam exit aperture (9) of the X-ray source ring (8); the first iris portion (11) is attached to or integrated into the detector ring (6); The detector ring (6) is configured to be axially displaceable together with the first diaphragm portion (11), so that the aperture of the diaphragm (10) can be adjusted by axial displacement of the detector ring (6). Computed tomography system.

2. The detector ring (6) and the X-ray source ring (8) are attached to the gantry (4) from different sides in the axial direction. The computed tomography system of claim 1 .

3. the second iris portion (12) is attached to or integrated with the X-ray source ring (8) or another portion of the gantry (4); The computed tomography system of claim 1 .

4. The detector ring (6) and the X-ray source ring (8) partially overlap each other in the axial direction. The computed tomography system of claim 1 .

5. the computed tomography system further comprises a patient couch (3) that can be moved axially into and out of the gantry (4); The detector ring (6) is attached to the gantry (4) in an axial direction from the side of the patient couch (3). The computed tomography system of claim 1 .

6. The detector ring (6) comprises a functional unit (62) that comprises detector elements (63) and can be individually removed from the gantry (4). The computed tomography system of claim 1 .

7. the detector ring (6) comprises at least one annular or partially annular housing piece (61); The housing piece (61) is configured such that at least one of the functional units (62) is at least partially inserted into the housing piece (61).

7. The computed tomography system of claim 6.

8. At least one of the functional units (62) is provided with a guide (64) oriented to allow accurate insertion of the functional unit (62) into the housing piece (61) with respect to positioning.

8. The computed tomography system of claim 7.

9. the housing piece (61) comprises a scattered beam collimator (65) oriented to shield the detector elements (63) of the detector ring (6) from scattered beams of the X-ray source ring (8); The housing piece (61) is inserted such that when the at least one functional unit (62) is inserted into the housing piece (61), the detector element (63) of the at least one functional unit (62) fits precisely with the scattered beam collimator.

8. The computed tomography system of claim 7.

10. the detector ring (6) includes a plurality of housing pieces (61) that, when assembled, define the annular shape of the detector ring (6); 8. The computed tomography system of claim 7.

11. Detector ring (6) for a computed tomography system, the detector ring (6) according to any one of claims 1 to 10, the detector ring (6) comprises at least one annular or partially annular housing piece (61) and one or more functional units (62) with detector elements (63), The housing piece (61) is configured such that at least one of the functional units (62) is at least partially inserted into the housing piece (61). Detector ring for a computed tomography system.

12. the detector ring (6) comprises a first iris portion (11) fixed to or an integral part of the detector ring (6); the first iris portion (11) together with the second iris portion (12) forms an iris (10) for an X-ray radiation ring having a diameter larger than the detector ring (6); Detector ring (6) according to claim 11.

13. A method for adjusting an aperture of a computed tomography system having a static gantry (4), the computed tomography system according to any one of claims 1 to 10, comprising: the gantry (4) comprises the detector ring (6), an X-ray source ring (8) having the beam exit aperture (9), and an annular aperture (10) having at least a first aperture portion (11) and a second aperture portion (12); the aperture (10) is arranged in front of the beam exit aperture (9) of the X-ray source ring (8); The first iris portion (11) is attached to the detector ring (6) or is integral with the detector ring (6), A step of axially displacing the detector ring (6), and thus the first iris portion (11), thereby changing the distance between the first iris portion (11) and the second iris portion (12) and adjusting the aperture of the iris (10); 23. A method for adjusting an aperture of a computed tomography system, comprising:

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