Rotating frame for the gantry of a computed tomography scanner, gantry and computed tomography scanner

Description

[0001] The invention relates to a bogie for the gantry of a computer tomograph, a gantry for a computer tomograph and a computer tomograph.

[0002] DE 10 2016 208328 A1 offers a bionic-inspired housing structure for a gantry, manufactured using a 3D printing process. DE 20 2021 106779 U1 offers a 3D-printed CT gantry that contains aluminum parts in the housing structure. In computed tomography (CT), cross-sectional images of the patient are reconstructed from X-ray projections from a variety of projection directions. To acquire the X-ray projections from different projection directions, an X-ray source and an X-ray detector positioned opposite it rotate around an acquisition area. In spiral CT, the patient to be examined is simultaneously guided on a couch through the tunnel of a gantry. All rotating components, in particular the X-ray source and the X-ray detector, are attached to a rotating frame in the gantry of the CT scanner. This rotating frame is also referred to as a rotating frame, drum, or rotating part of the gantry.The gantry also typically has a fixed support frame to which cladding elements are attached. The bogie is rotatably mounted within this support frame, for example, by means of a roller bearing or magnetic bearing.

[0003] To reduce radiation exposure to the patient as much as possible and to avoid motion artifacts, efforts are made to enable the highest possible rotation speed for the X-ray source and X-ray detector, for example, up to 240 rpm. Therefore, the bogie must meet the highest rigidity requirements to prevent deformation even at high rotation speeds. Slight deformations of just a few tenths of a millimeter can result in severe image artifacts if the relative position of the X-ray source to the X-ray detector does not remain exactly constant. In the current state of the art, the bogie is therefore designed as an aluminum or steel casting with a relatively thick wall thickness of approximately 20-25 mm. Such a casting provides the required rigidity and a high section modulus against load.Furthermore, the bogie in the prior art typically has a pot or drum shape, ensuring that the rotating components are held stable even at high rotation speeds. Such a bogie is disclosed, for example, in DE 10 2013 227 060 A1.

[0004] During each examination, the bogie, including the X-ray source and other rotating components, is accelerated as quickly as possible to the rotation time required for the examination, which requires corresponding energy from the bogie's drive motor.

[0005] The invention is based on the object of providing a bogie with an alternative to known fastening options for the rotating components of the computer tomograph.

[0006] These objects are achieved by a bogie according to claim 1, by a gantry according to claim 12, and by a computer tomograph according to claim 13.

[0007] The bogie according to the invention has mounting areas to which rotating components of the CT scanner can be attached and is characterized by being manufactured at least partially by additive manufacturing. Additive manufacturing, also known as 3D printing, refers in particular to manufacturing processes in which material is applied layer by layer to produce three-dimensional workpieces. This is typically done computer-controlled from liquid or powdered materials according to a CAD plan, allowing any three-dimensional (3D) shape to be realized.

[0008] By at least partially manufacturing the bogie using additive manufacturing, it is possible to optimize the structure of the bogie toward lightweight construction while simultaneously achieving maximum dimensional rigidity. For example, a 3D-printed bogie according to the invention with a structurally optimized design can be provided. The great design freedom in the bogie's shape makes it possible to achieve low weight, particularly through low wall thicknesses and / or the use of material with a low specific weight, while still providing sufficient rigidity or dimensional rigidity for the required high rotational speeds, or even for even higher rotational speeds than currently usual. In particular, the bogie according to the invention can be suitable for rotational speeds of over 260 rpm, preferably approximately 280-320 rpm.

[0009] The weight reduction of the bogie also has the advantage of reducing the static load on the gantry's rotation bearing. Furthermore, the overall weight of the gantry is reduced, thus reducing transport costs and floor load at the customer's site. Most importantly, less rotation and acceleration energy is required, as the weight of the rotating unit (bogie and rotating components) is reduced. This allows for a smaller rotation motor and / or faster acceleration to rated speed, which in turn translates into shorter patient waiting times and higher patient throughput.

[0010] When manufacturing bogies using additive manufacturing, the topology or structure of the bogie can be optimized using an algorithm. This allows even unconventional, non-rotationally symmetrical topologies to be calculated, for example, to withstand the expected loads at a given high speed. Safety elements can also be specified during the calculation, for example, to prevent complete failure in the event of a local crack in the bogie.

[0011] "Rotating components" of a CT scanner refer to all components that rotate around the patient during CT data acquisition, particularly the X-ray source and X-ray detector. Typically, the rotating components are attached to the rotating frame in the assembled CT scanner. Other rotating components can include, for example, filters and apertures mounted in front of the X-ray tube, a radiator cooling system, a voltage generator, and other electronic devices necessary for operating the X-ray tube and X-ray detector, provided these cannot be arranged stationary outside the rotating frame but must be directly connected to the X-ray source and X-ray detector for operation. The acquisition area for a rotating component is the area in which this component is to be arranged in the assembled CT scanner and attached to the rotating frame.

[0012] The bogie can be manufactured at least partially using one of the following additive manufacturing processes: Fused Deposition Modeling (FDM), Selective Laser Melting (SLM), Selective Laser Sintering (SLS), Electron Beam Melting (EBM), Directed Energy Deposition (DED).

[0013] A preferred method is the DED process because it offers maximum design freedom while being suitable for many materials, including metals. It is also suitable for hybrid applications, for example, attaching elements to existing workpieces. With DED, a high-power laser can be used to melt metal powder, which is fed into the focus of the laser beam. The laser beam usually passes through the center of a coating head and is focused into a small spot by one or more lenses. The metal powder is fed and distributed around the circumference of the coating head or can be fed through nozzles arranged around the coating head. The build takes place on a single-plane movable table that moves along a track created from a digital model to produce an object layer by layer.The coating head is moved vertically upward as each layer is completed. Some systems even utilize 5-axis or 6-axis systems (i.e., articulated arms), capable of depositing material onto the workpiece with few to no spatial access restrictions. The DED process is suitable for a wide range of materials, such as titanium, stainless steel, aluminum, tungsten, and other specialty materials, as well as composites. The process can not only be used to create entirely new workpieces, but can also be used to add material to existing parts, for example, for hybrid manufacturing applications.

[0014] Selective laser sintering (SLS) is also very suitable. This involves using a laser as a heat source to sinter powdered material (e.g., nylon or polyamide). The laser is automatically directed to points in space defined by a 3D model, bonding the material into a solid structure. There are rapid 3D printing processes for this, but in these processes, the workpiece is sintered after printing to ensure a sufficiently strong and rigid bond.

[0015] Additive manufacturing methods for plastics are also possible, in which the bogie is constructed at least partially from fiber-reinforced plastic.

[0016] The bogie can be made at least partially from one of the materials selected from steel, a steel alloy, aluminum, an aluminum alloy, fiber-reinforced plastic, a titanium alloy, a chromium-cobalt alloy, or a magnesium alloy. Preferably, it is made at least partially from a material that is suitable for additive manufacturing and / or is relatively lightweight, such as aluminum and aluminum alloys and / or fiber-reinforced plastic (FRP), in particular glass-fiber-reinforced plastic (GFRP) or carbon-fiber-reinforced plastic (CFRP). GFRP or CFRP can be processed using additive manufacturing so that the fibers run in the direction of force, making them particularly suitable for the production of reinforcement elements, struts, or truss elements in lightweight construction.

[0017] According to one embodiment, the bogie has struts manufactured using additive manufacturing. A strut is, for example, a strut, beam, or truss element that connects two points of the bogie in a force-fitting manner. In particular, a strut can absorb forces along its longitudinal direction. One or more recesses can be located between the strut and other areas of the bogie. Struts can achieve particularly high dimensional rigidity with the lowest possible weight, but they are not easy to manufacture using conventional bogie manufacturing processes, such as aluminum sand casting. This is especially true if the struts are to be provided on multiple levels. Using additive manufacturing, however, struts can be manufactured in any shape and direction.

[0018] According to a preferred embodiment, the bogie has at least one strut manufactured by additive manufacturing, which connects two points on an annular element arranged around the axle, in particular on the outer circumference of the bogie, in particular in the manner of a chord, whereby the strut does not have to be straight. The strut can, for example, be curved outwards, as seen from the axle. Such a strut can achieve a high degree of dimensional rigidity of the bogie, especially on its outer circumference, even at high speeds. Advantageously, two to three such struts are provided, each connecting points at an angular distance of 90 to 170 degrees.

[0019] The bogie is typically rotatable about an axis, which in the installed CT scanner usually runs horizontally through the center of the gantry. The rotating components of the CT scanner can be arranged roughly in a ring around this axis. For this purpose, conventional bogies made of sand-cast aluminum often have a base plate that has the basic shape of a round perforated disc and merges at the outer circumference into a roughly cylindrical drum that encloses the rotating components in the circumferential direction. However, a casting cannot have any undercuts starting from the base plate, as this would require a lost mold. The drum cannot therefore curve back inwards, for example to hold one of the rotating components from two sides.

[0020] The bogie according to the invention has at least one undercut formed by additive manufacturing. This can mean that sections of the bogie thicken and / or bulge in the axial direction, in any case not remaining within their axial footprint. An undercut can also be a section of the bogie that at least partially encloses a receiving area for a rotating component of the computed tomography scanner, so that it is enclosed, in particular, from two opposite sides.

[0021] The undercut formed by additive manufacturing contributes to such a receiving area being at least partially encompassed by sections of the bogie on two sides, which enables a particularly stable attachment of the rotating component. In particular, it can be provided that the receiving area can be surrounded by the bogie sections on both sides in the axial direction and / or in the circumferential direction and / or in the radial direction, particularly preferably in the axial direction and / or in the radial direction.

[0022] The bogie may have the shape of a hollow body, in which in particular receiving areas may be surrounded by walls and / or struts of the bogie.

[0023] In particular, the bogie can have the approximate shape of an inwardly open torus, with the outer surface of the torus preferably provided with recesses and / or at least partially formed by struts or trusses. The rotating components can be inserted into the bogie from the inside, i.e., from the axle. The torus does not have to be spanned by a circle, but can also have an approximately oval, square, parallelogram, or rectangular cross-section, possibly with rounded corners. Such a body, essentially formed by struts or trusses, is also referred to as a "bird's nest."

[0024] The bogie may also have the shape of a hollow ring or tire, whereby this shape also preferably has walls provided with recesses and / or struts or trusses.

[0025] According to one embodiment, the bogie is designed as a lightweight construction, in particular with an average wall thickness of up to 30 mm, preferably 5 mm to 20 mm, more preferably 10-18 mm. Additive manufacturing makes it possible to optimize the structure of the bogie such that its walls and struts can be designed with a very thin wall thickness without sacrificing rigidity. This can be achieved by the struts, on the one hand, and by the optimized basic shape, such as the tire or bird's nest shape, on the other.

[0026] According to one embodiment, the bogie weighs 20%-60%, preferably 30%-50%, less than a corresponding bogie made of cast aluminum according to the prior art.

[0027] According to one embodiment, the bogie weighs less than 200 kg, preferably less than 160 kg, more preferably 100-140 kg. These specifications refer to a bogie with an inner diameter of 60-100 cm, preferably 70-90 cm, in particular 80 mm, and an outer diameter of 1500 mm to 18000 mm, in particular 1600 mm to 1700 mm, e.g., 1650 mm, and without the rotating components. A bogie of this size manufactured conventionally using aluminum sand casting, in contrast, has a mass of approximately 240 kg. For smaller bogies, e.g., for head CT scanners, there is a similarly large weight savings potential in percentage terms. The weight savings achievable through additive manufacturing and the optimized structure are therefore considerable.

[0028] According to one embodiment, the bogie has a frame not manufactured by additive manufacturing and further elements manufactured by additive manufacturing. This allows the advantages of conventional and additive manufacturing processes to be advantageously combined. For example, it is possible to produce a frame cost-effectively, e.g., from a rolled metal element, in particular a rolled flat plate made of aluminum alloy or steel. The frame can, for example, have the basic shape of a round perforated disc punched from a rolled metal product. Alternatively, the frame can also be a cast part made of metal or plastic, or made from a continuously cast metal element. Finally, the frame can also be made from a cylindrical, round-rolled or continuously cast metal part. The frame can additionally be machined, e.g.by turning or milling, for example to create recesses.

[0029] According to one embodiment of the invention, additional elements manufactured by additive manufacturing are attached to such a "base frame," which contribute in particular to the stabilization and dimensional rigidity of the bogie. This can be achieved by manufacturing the additional elements separately using additive manufacturing and then connecting them to the frame, e.g., by welding, gluing, form-fitting, using fasteners such as screws or rivets, or a combination of these connections. This has the advantage that the additional elements can be manufactured particularly cost-effectively and that their design allows for a particularly high degree of freedom. The connected elements are, in particular, struts. It is also possible to attach the additional elements directly to the frame using additive manufacturing. This has the advantage of eliminating an additional connection step.In this case, the frame can be clamped into the tool for additive manufacturing and the other elements can be directly attached to the base frame, e.g. . be built by DED.

[0030] According to an alternative embodiment, the bogie is manufactured entirely by additive manufacturing. This allows for a very extensive optimization of the design. The bogie can be manufactured as a single piece, but it can also be constructed from several interconnected elements, with the individual elements again being manufactured by additive manufacturing. This allows the combination of different materials, particularly metal with fiber-reinforced plastics, which allows for a particularly weight-saving design.

[0031] According to one embodiment, the bogie comprises a plurality of interconnected elements, at least one of which is manufactured by additive manufacturing. For example, one or more elements manufactured by additive manufacturing, such as struts, can be connected to a frame not manufactured by additive manufacturing, as described above. Advantageously, at least 20%, preferably 35%, and more preferably 50% of the mass of the bogie is manufactured by additive manufacturing.

[0032] According to one embodiment, the bogie has truss elements that enclose at least one receiving area for a rotating component of the CT device on at least one side, preferably on two or three sides. The truss can in particular be a rod structure whose bars are connected to one another at their ends at nodes. Advantageously, the bars are predominantly or entirely loaded by forces along their longitudinal direction, in particular tensile. This makes it possible to achieve a particularly high degree of dimensional rigidity of the bogie with minimal use of material. The truss elements or a truss formed by them can form a wall of the bogie, in particular a wall on an outer circumferential surface of the bogie, or a wall in the form of a flat or curved perforated disc, which approximately takes on the function of the base plate of the conventional bogie.

[0033] According to one embodiment, the bogie has at least one continuous ring to which elements produced by additive manufacturing, in particular struts, are attached. The ring can also be produced by additive manufacturing; it can also be manufactured conventionally, for example as a cast part or extruded and / or bent part. The ring advantageously defines the inner diameter of the bogie. Its axis can coincide with the axis of the bogie. The bearing on which the bogie is rotatably mounted can be located on such an inner ring in the assembled CT device. Struts can run from such an inner ring, in particular radially outwards, optionally with a curvature towards the axial direction, in order to form a receiving area for a rotating component.

[0034] According to an advantageous embodiment, at least some of these struts are connected at their other end to a ring which runs in particular coaxially to the inner ring. This ring can be arranged on the outer circumference of the bogie, i.e. on the outside in the radial direction. This outer ring can enclose the rotating components on the outside; if necessary, rotating components can also be attached to the outer ring. The outer ring can be offset in the axial direction relative to the inner ring. According to one embodiment, struts are attached to the outer ring to stabilize the outer ring, in particular to prevent its deformation at high speeds. These can be chord-like struts which each connect two points on the outer ring which are spaced apart by 90° to 170° in the circumferential direction.Such tendon-like struts can in turn be connected to further struts extending to the outer ring. The tendon-like struts can enclose a receiving area on a side opposite the inner ring, thus enabling the secure holding of rotating components.

[0035] The inner and / or outer ring of the bogie can be manufactured using additive manufacturing. However, it can also be produced using a conventional process, such as bending metal bars or stamping from a rolled metal flat product. Preferably, the aforementioned struts are manufactured using additive manufacturing, in particular by being attached to the inner and / or outer ring.

[0036] According to one embodiment, the bogie has such rigidity that it can be deformed by a maximum of 0.3 mm, preferably up to 0.2 mm, during rotation during operation of the computed tomography scanner. Rotation here refers to a rotation speed of at least 240 rpm, preferably at least 300 rpm. According to the prior art, significantly higher deformation is to be expected at such speeds, in particular up to 0.6 mm or even more.

[0037] The invention also relates to a gantry for a computed tomography scanner with a rotating frame as described herein, to which rotating components of the computed tomography scanner, in particular an X-ray source and an X-ray detector unit, are mounted. The gantry typically has conventional dimensions and, in addition to the rotating frame and the rotating components installed therein, can also comprise a support frame and a casing.

[0038] According to a further aspect, the invention is also directed to a computed tomography scanner having a bogie and / or a gantry according to the invention. The computed tomography scanner may further comprise a gantry as described above. Additional components, such as a computer for reconstructing the acquired data and an operating console, may also be part of the computed tomography scanner. All advantages and embodiments described with reference to the bogie also apply to the gantry and the computed tomography scanner, and vice versa.

[0039] The invention will now be described in more detail using exemplary embodiments with reference to the accompanying drawings. In the drawings: Fig. 1 shows a schematic perspective view of a computer tomograph according to an embodiment of the invention; Fig. 2 shows a schematic plan view of a bogie; Fig. 3 shows a perspective view of a bogie according to the prior art; Fig. 4 shows a perspective view of a bogie according to an embodiment of the invention from a first side; Fig. 5 shows a perspective view of a bogie according to Figure 4 from a second side; Fig. 6 shows a schematic sectional view of a further embodiment of a bogie; Fig. 7 shows a schematic sectional view of yet another embodiment of a bogie.

[0040] Identical or similar elements are identified by the same reference numerals in the figures.

[0041] Figure 11 shows a simplified view of a CT scanner 1 with a gantry 2 in which a rotating frame 30 according to the invention is accommodated. This frame is mounted on a support frame 5. The gantry 2 is provided with a cover 3. It has an annular opening through which the bed 4 can be advanced. A ring 7 extends around the annular opening, on which the rotating frame is mounted, e.g., by a roller bearing, so that it can rotate around a patient lying on the bed 4. The drive mechanism for the rotation is not shown.

[0042] Figure 2shows a schematic plan view of a bogie 8 according to the prior art. The bogie has a base plate 10 to which the rotating components 20 are attached. The rotating components of the 20-inch computed tomography scanner are, in particular, an X-ray tube 22 and an X-ray detection unit 24. Other components not shown in Figure 2, but which can be arranged around the further periphery of the bogie 8, include, for example, high-voltage generators and cooling systems.

[0043] Figure 3shows a bogie 8 according to the prior art. This is a metal casting, in particular, it is manufactured by aluminum sand casting. The bogie 8 has a base plate 10, which has the basic shape of a round perforated disk, but is provided with recesses 13. A drum-like, continuous wall 9 is provided on the outer circumference. This wall 9 has a relatively thick wall thickness of over 20 mm, since it must absorb high forces during the rotation of the bogie 8 with the rotating components 20 without deforming too much, since otherwise the X-ray tube 22 and the detector unit 24 would lose their relative position to one another. A lower projection 14 is provided on the inner radius of the bogie 8. In the radial direction, intermediate walls 16 are arranged on the base plate 10, which separate the individual receiving areas 12 for the rotating components of the gantry from one another.Thus, the bogie 8 forms receiving areas 12 for rotating components 20 of the CT scanner, which are enclosed in particular by the walls 9, 14, and 16. However, due to the sand-casting process, it is not possible for the outer wall 9 to, for example, curve inward again or form an undercut, although this would be helpful for securing the rotating components 20. Furthermore, the bogie 8 is very heavy.

[0044] Figure 4shows a bogie 30 according to an embodiment of the invention. This is a lightweight construction using additive manufacturing. It has an inner ring 34 with a diameter suitable for mounting on the ring 7 of the gantry. Furthermore, an outer ring 36 is provided, to which the truss-like structure is attached to the outer circumference of the bogie 30. Struts 32 of irregular shapes and thicknesses run between the inner ring 34 and the outer ring 36. These shapes and thicknesses were calculated based on the weight of the rotating components 20 to be used in order to ensure optimal rigidity and stability with the lowest possible weight. Furthermore, two chord-like struts 38 are arranged on the outer ring 36. These struts arch over the receiving areas for the rotating components and support the outer ring 36 and protect it from deformation.When the bogie 30 rotates with the rotating components 20 inserted and at high speed, forces in the direction of the arrows F are to be expected, which, without the struts 38, would lead to a deformation of the bogie 30, in particular of the ring 36 on the outer circumference. By manufacturing using additive manufacturing, it is now possible to provide reinforcing elements, such as struts, in two or more planes spaced apart from one another in the axial direction, as shown in the example of the . Figure 4 the struts 32 and 38. The resulting shape is also called a bird's nest. The bogie 30 of the Figure 4is manufactured entirely by additive manufacturing. However, it is also possible to manufacture the inner ring 34 and, if necessary, the outer ring 36 conventionally, and then, using hybrid technology, to attach the intermediate elements, in particular the struts 32 and 38, to the rings by additive manufacturing.

[0045] Figure 5 shows the bogie 30 of the Figure 4 from the other side. Here, the numerous struts 32 are particularly clearly visible. These are irregularly shaped and form a kind of framework connecting the inner ring 34 with the outer ring 36. Some of the struts 32 are also flat, as can be seen, for example, at 33.

[0046] Figure 6shows a cross-section along the axis 40 through a bogie 30 according to another embodiment. This bogie 42 has a base frame 42, which has approximately the shape of a round perforated disc. A drum-shaped wall 44 is then attached to the outside in the radial direction, which, offset in the axial direction from the base frame 42, curves inwards again at 46. This forms an undercut at 46, and a rotating component 20 arranged in the receiving area 12 is securely held. In other words, a rotating component 20 can be encompassed from two sides by elements of the bogie, namely the base frame 42 and the undercut 46. Both the base frame 42 and the drum-like part 44 and the section 46 are preferably formed essentially from struts or trusses.

[0047] Figure 7shows a cross-section along axis 40 through a bogie according to yet another embodiment. In this case, the bogie 30 has the shape of an inwardly open torus or hoop 48. Here, too, the wall 48 of the bogie is preferably formed from struts, which in particular form a truss.

Claims

1. Rotating frame (30) for the gantry (2) of a computed tomography unit (1), which has receiving areas (12), to which rotating components (20, 22, 24) of the computed tomography unit can be attached, wherein the rotating frame (30) is produced at least in part using additive manufacturing, characterised in that it has undercuts (46) formed by means of additive manufacturing, wherein an undercut of the undercuts (46) designed by means of additive manufacturing contributes to a receiving area of the receiving areas (12) being encompassed at least in part from two sides by sections of the rotating frame (30).

2. Rotating frame (30) according to claim 1, characterised in that it has struts (32, 38) formed by means of additive manufacturing.

3. Rotating frame (30) according to one of the preceding claims, characterised in that the rotating frame (30) is rotatable about an axis (40), wherein the receiving area is encompassed in the axial direction from two sides by the sections of the rotating frame (30).

4. Rotating frame (30) according to one of the preceding claims, characterised in that the rotating frame (30) is lightweight in construction, in particular with an average wall thickness of up to 20 mm.

5. Rotating frame (30) according to one of the preceding claims, characterised in that the rotating frame (30) weighs 20%-60%, preferably 30%-50%, less than a corresponding rotating frame made of cast aluminium in accordance with the prior art.

6. Rotating frame (30) according to one of the preceding claims, characterised in that it has a frame (42) not produced using additive manufacturing, as well as further elements produced using additive manufacturing.

7. Rotating frame (30) according to claim 6, characterised in that the frame (42) is produced from a rolled metal element.

8. Rotating frame (30) according to one of claims 1 to 5, characterised in that it is completely produced using additive manufacturing.

9. Rotating frame (30) according to one of the preceding claims, characterised in that it has bracing elements which enclose at least one receiving area on at least one side.

10. Rotating frame (30) according to one of the preceding claims, characterised in that it has at least one continuous ring (34, 36), on which struts are positioned by means of an additive manufacturing process.

11. Rotating frame (30) according to one of the preceding claims, characterised in that the rotating frame (30) has a rigidity, such that during a rotation in operation of the computed tomography unit it is maximally deformable by up to 0.3 mm, preferably up to 0.2 mm.

12. Gantry (2) for a computed tomography unit with a rotating frame (30) in accordance with one of the preceding claims, to which are attached rotating components (20, 22, 24) of the computed tomography unit (1), in particular an X-ray source (22) and an X-ray detector unit (24).

13. Computed tomography unit (1), comprising the rotating frame (30) according to one of claims 1 to 11 and / or the gantry (2) according to claim 12.