Trajectory of a C-arm of a C-arm system

Abstract

A method for controlling a C-arm (2) of a C-arm system (1) is described. In this method, a forward rotation of the C-arm (2) is performed. The forward rotation begins at a starting position (SP). v ) the forward movement of the C-arm (2) with a lateral offset (lv) with a first offset value (-D) is started and the C-arm is moved forward to an end position (EP) v ) of the forward movement rotates, whereby the lateral offset (lv) is reduced to a value of 0. Furthermore, a reverse rotation of the C-arm (2) is performed. The reverse movement is completed at the end position (EP). v ) of the forward run is started and the C-arc (2) is moved backwards to an end position (EP) r) of the reverse run rotates, with the lateral offset (lv) in the opposite direction to the lateral offset (lv) of the forward run up to a second offset value (+D) at the end position (EP) r The reverse rotation speed is increased. Furthermore, an imaging method for generating 3D image data (BD) of an object under investigation (0) is described. A control device (50) is also described. Additionally, a C-arm system (1) is specified.

Description

[0001] The invention relates to a method for controlling a C-arm of a C-arm system. The method involves forward rotation of the C-arm and reverse rotation of the C-arm. The invention also relates to an imaging method for generating 3D image data from an examination subject. Furthermore, the invention relates to a control device. Furthermore, the invention relates to a C-arm system.

[0002] With the help of modern imaging techniques, two- or three-dimensional image data is generated, which can be used to visualize an imaged object under examination and also for other applications.

[0003] Imaging techniques are often based on the detection of X-rays. An X-ray system usually comprises an X-ray source and an X-ray detector located opposite the X-ray source. During imaging, an object to be examined, in particular a patient, from whom an image is to be taken, is positioned in the space between the X-ray source and the X-ray detector. One type of X-ray system is the so-called C-arm system. In these X-ray systems, the X-ray source and the X-ray detector, usually a flat detector, are attached to a C-shaped support element, also called a C-arm. Due to its shape, the C-arm and with it the associated diagnostic and treatment device or the X-ray detector can be moved orbitally around a point on a patient to be examined or treated, in order to achieve different angular positions between the patient and the diagnostic or treatment device.X-ray detector without having to reposition the patient.

[0004] If a part of the area to be examined or treated is to be imaged from a different position, or if the imaging system or X-ray detector is to be moved during an image of a larger area of ​​the object to be examined, the C-arm, for example, is rotated around a support axis which is connected to the center of the C-arm.

[0005] 3D imaging using C-arm angiography systems is now established in the interventional setting. However, a significant limitation compared to conventional CT systems is the limited imaging area caused by the size of the flat-panel detector. This limited imaging area means that many organs (e.g., lungs, liver) cannot be captured with a single image. Furthermore, the projection data for almost all body regions are laterally clipped or truncated, which leads to image artifacts (truncation artifacts) in common reconstruction techniques.

[0006] Solutions used clinically to date for C-arm 3D imaging with a large imaging field require that the relative position of the focal point (i.e., the point of impact of the electrons on the anode of the X-ray source or the point from which the X-ray photons of the X-ray radiation are emitted) to the measurement object (patient) is identical. In existing "large volume" protocols on robotic systems, the focal point moves in a circular trajectory around the patient. Therefore, the distance to the patient remains constant. For angiography systems with a rigid C-arm, this requires that the isocenter point of the C-arm be dynamically shifted laterally in both directions in the rotation plane during rotation around the patient, which is only possible with complex robot mechanics.

[0007] For classic isocentric angiography systems, a trajectory with a laterally shifted isocenter point is used. This involves a forward and a backward scan and simultaneously additional one-dimensional lateral movements in the rotation plane. This trajectory, which is Fig. 1, places far less demands on the mechanical design of a C-arm system and enables large 3D imaging areas even with simple C-arm systems. However, the Fig. 1 shown trajectory still has practical disadvantages: - The end point of the forward scan does not correspond to the start point of the reverse scan. Therefore, the system must be moved between scans. This can result in a time delay of several seconds. Since the patient must hold their breath during the scan, the time delay should be kept as short as possible. - The direction of movement in the lateral direction changes during a run. In the AP direction (AP is an acronym for "anterior-posterior"), the sign of the velocity in the lateral direction therefore changes. This change can lead to irreproducible geometric inaccuracies, especially in typical ceiling-suspended systems. Since 3D reconstruction requires very high geometric accuracy of the image, this can lead to image artifacts.

[0008] It is therefore an object of the present invention to provide a method and a control device for controlling a C-arm with which imaging can be carried out in a time-saving manner and with reduced image artifacts.

[0009] This object is achieved by a method for controlling a C-arm of a C-arm system according to patent claim 1, by an imaging method for generating 3D image data from an examination object according to patent claim 10, by a control device according to patent claim 11 and by a C-arm system according to patent claim 12.

[0010] In the method according to the invention for controlling a C-arm of a C-arm system, preferably a ceiling-suspended C-arm system, a forward rotation of the C-arm is performed, as already mentioned at the beginning. The forward rotation is started at a starting position of the forward rotation of the C-arm with a lateral offset with a first offset value. A lateral offset is to be understood as a displacement of the C-arm in the horizontal direction transverse to the patient bed. This also shifts the focal point of the X-ray source of the C-arm system in the transverse direction. The C-arm is then rotated in the forward direction to an end position of the forward rotation, wherein the lateral offset is monotonically reduced to a value of 0. The end point of the forward rotation has, in addition to the aforementioned value of 0 for the offset, a predetermined value of an orbital angle β.As explained in more detail later, the value for the orbital angle of the start point and the end point is selected so that a sufficiently extensive angular range around the object under examination can be covered by imaging. Preferred values ​​for the orbital angle β of the start points and end points of the forward scan are at least 90° and -90°, respectively. Particularly preferred values ​​for the orbital angle β of the start points and end points of the forward scan are 100° and -100°, respectively. Also preferred are values ​​for the orbital angle β of the start points and end points of the forward scan that lie within interval ranges of [90°, 120°] and [-90°, -120°]. For mechanical reasons, a ceiling-suspended system, in particular, cannot achieve arbitrary angulations. It might be possible to shift the start / end angles by up to 20° (from the ideal value = 100°); further than that, the system is generally unable to rotate mechanically.

[0011] As also mentioned at the beginning, a reverse run of a rotation of the C-arm is then performed, i.e. a rotation in the opposite (rotational) direction to the forward run. The reverse run is first started at the end position of the forward run and then the C-arm rotates in the reverse direction until it reaches the end position of the reverse run. During the rotation, the lateral offset is monotonically increased in the opposite direction to the lateral offset of the forward run up to a second offset value at the end position of the reverse run. “Increased” should refer to an increase in the amount of the lateral offset. For example, if the lateral offset is positive during the forward run, the lateral offset is negative during the reverse run. If the lateral offset is negative during the forward run, the lateral offset is positive during the reverse run.Advantageously, the trajectory of the forward run and the backward run differ so that additional image information can be obtained from a patient during the backward run.

[0012] In contrast to conventional control methods, in the method according to the invention, the end point of the forward scan corresponds to the start point of the reverse scan. Advantageously, the C-arm does not need to be moved between the forward scan and the reverse scan. Since the patient must hold their breath during the scan, a time delay between the forward scan and the reverse scan is advantageously avoided or kept as short as possible.

[0013] In addition, it is advantageously achieved that the direction of movement of the C-arm in the lateral direction is not changed during a run, i.e. during the forward run and during the backward run.

[0014] Such a change in the direction of movement during a scan, especially with typical ceiling-suspended systems, can lead to irreproducible geometric inaccuracies with conventional procedures. Since 3D reconstruction requires very high geometric accuracy of the image, these inaccuracies can lead to image artifacts. Such image artifacts are now advantageously avoided because the direction of movement during the lateral movement of the C-arm is maintained within the motion sequence of the forward scan and the reverse scan.

[0015] In the imaging method according to the invention for generating 3D image data from an examination subject, projection data from the examination subject is acquired by applying the method for controlling a C-arm of a C-arm system, and 3D image data is reconstructed based on the acquired projection data. Advantageously, the imaging method according to the invention can be used to acquire 3D image data from an examination subject, preferably a patient, with improved quality.

[0016] The control device according to the invention has a start unit for controlling a start position of a C-arm in a forward run of a rotation of the C-arm with a lateral offset with a first offset value and for starting the forward run at the start position of the forward run and for starting a reverse run of a rotation of the C-arm at an end position of the forward run.

[0017] The control device according to the invention also has a rotation unit for rotating the C-arm in the forward direction during forward travel up to the end position of the forward travel, wherein the lateral offset is reduced to a value of 0, and for rotating the C-arm in the reverse direction up to an end position of the reverse travel, wherein the lateral offset is increased in the opposite direction to the lateral offset of the forward travel up to a second offset value at the end position of the reverse travel. The control device according to the invention shares the advantages of the method according to the invention for controlling a C-arm of a C-arm system.

[0018] The C-arm system according to the invention comprises a C-arm, preferably a C-arm-shaped support element, which is rotatable or pivotable about at least one rotation or pivot axis. Furthermore, the C-arm system according to the invention comprises an X-ray source arranged at a first end of the C-arm, preferably the C-arm-shaped support element, and an X-ray detector arranged opposite the X-ray source at a second end of the C-arm. Furthermore, the C-arm system according to the invention comprises the control device according to the invention. The C-arm system according to the invention shares the advantages of the method according to the invention for controlling a C-arm of a C-arm system.

[0019] A large part of the aforementioned components of the control device and the C-arm system can be implemented wholly or partially in the form of software modules in a processor of a corresponding computer system. A largely software-based implementation has the advantage that even previously used computer systems can be easily retrofitted with a software update in order to operate in the manner according to the invention. In this respect, the object is also achieved by a corresponding computer program product with a computer program that can be loaded directly into a computer system, with program sections in order to carry out the steps of the method according to the invention for controlling a C-arm of a C-arm system when the program is executed in the computer system. Such a computer program product can, in addition to the computer program, optionally contain additional components such as, for example,include documentation and / or additional components, including hardware components such as hardware keys (dongles, etc.) for using the software.

[0020] A computer-readable medium, e.g., a memory stick, a hard disk, or another portable or permanently installed data storage device, can be used for transport to the computer system or control device and / or for storage on or in the computer system or control device, on which the program sections of the computer program that can be read and executed by a computer system are stored. For this purpose, the computer system can, for example, have one or more cooperating microprocessors or the like.

[0021] The dependent claims and the following description each contain particularly advantageous embodiments and developments of the invention. In particular, the claims of one claim category can also be developed analogously to the dependent claims of another claim category. Furthermore, within the scope of the invention, the various features of different embodiments and claims can also be combined to form new embodiments.

[0022] In one embodiment of the method according to the invention for controlling a C-arm of a C-arm system, the starting position of the forward run of the C-arm has a first angular position. Furthermore, the end position of the forward run has a second angular position, and the end position of the reverse run has a third angular position. The first angular position, the second angular position, and the third angular position preferably have an angle with the same absolute value. Advantageously, a symmetrical angular range is traversed by the C-arm, and thus also by the X-ray detector and the X-ray source, during the forward run and the reverse run. Advantageously, a patient lying on a patient couch symmetrically to the AP position (anterior-posterior position, the patient is irradiated from a vertical direction, the orbital angle is 0°) can be imaged from both sides from angles of the same absolute value.

[0023] To acquire sufficient data for a 3D reconstruction, at least one arc with an angle of 200° must be traversed. It is therefore advisable to rotate along an arc of 100° to the left and right of the AP plane. For mechanical reasons, a ceiling-suspended system, in particular, cannot traverse arbitrary angulations. It might be possible to shift the start / end angles by up to 20°; the system cannot rotate any further.

[0024] Preferably, the first angular position has an angle of 100°, the second angular position has an angle of -100°, and the third angular position has an angle of 100°. Image data can advantageously be acquired from an angular range of 200°, so that an examination area or object can be imaged from different directions. The image information acquired from different directions can advantageously be combined to create a 3D image of the examination area.

[0025] Therefore, an orbital angle of 100° is preferably used as the starting position for the forward run, and an orbital angle of -100° is preferably used as the end position for the forward run. Furthermore, an orbital angle of -100° is used as the starting position for the reverse run, and an orbital angle of 100° is used as the end position for the reverse run. As already mentioned above, an angular range of at least 200° should preferably be traversed for both the forward and reverse runs. Likewise, the traversed angular range should preferably be within a value range of 180° to 240 degrees, particularly preferably within a value range of 190° to 210°.

[0026] Particularly preferably, the first offset value and the second offset value have the same amount. Since patients are typically approximately symmetrical to the sagittal plane, it is advisable to use an offset that is uniform in both directions.

[0027] In a likewise particularly preferred variant of the method according to the invention for controlling a C-arm of a C-arm system, the rotation of the C-arm in the forward direction during the forward run comprises the following steps: - Maintaining the first offset value of the lateral offset in the forward run between the start position and an AP position, - gradually reducing the lateral offset between the AP position and a lateral position to 0, - Maintain the lateral offset with the value 0 from the range of the lateral position to the end position of the forward run.

[0028] Advantageously, the first offset value, which is used for the lateral offset at the start of the forward run, is continuously reduced until the lateral position is reached, so that uniform imaging is enabled.

[0029] Alternatively, the offset in the forward run can be reduced to 0 not at the lateral position, but only until the end position. This advantageously achieves a continuous change of the offset until the end position.

[0030] Preferably, the reverse run includes rotating the C-arm in the reverse direction: - Maintaining the lateral offset with the value 0 in the range from the end position of the forward run to the lateral position, - Gradually increasing the lateral offset during rotation in the positive lateral direction between the lateral position and the AP position to a final value, wherein the lateral offset is in the opposite direction to the lateral offset of the forward run, - Maintain the offset between the AP position and the end position of the reverse run.

[0031] Advantageously, no offset change occurs in the "right" quadrant, i.e., during forward and reverse travel. This is because an offset change in the right quadrant would have to be compensated by a movement in the opposite direction in the left quadrant. If the offset change occurs in both directions during travel, this has the disadvantage described above that the direction of the movement in the lateral direction changes during a run, as is the case with the Fig. 2. Therefore, it is advantageous to set the offset in one direction before starting the rotation, so that during the rotation in the right quadrant the offset is not changed, and during the return the offset is simply left the same until the end.

[0032] In a likewise preferred variant of the method according to the invention for controlling a C-arm of a C-arm system, the maximum value of the lateral offset depends on the detector width. The maximum lateral offset should be selected such that the image recordings acquired from the same angle during the forward and reverse scans connect. If the same value, but with opposite signs, is selected as the maximum lateral offset in the forward and reverse scans, the offset should be a maximum of half the detector width. If the maximum lateral offset is smaller, an overlap region results between the image data of the forward scan and the reverse scan, which were acquired with the same orbital angle. Advantageously, adjacent image recordings can be combined more easily due to the overlap.

[0033] Likewise preferably, in the method according to the invention for controlling a C-arm of a C-arm system, the maximum value of the lateral offset depends on the overlap of the X-ray detector in the forward and reverse scans. The overlap can assume values ​​from 0 to 1. A value of "0" means that there is no overlap, and a value of "1" means that the images acquired with a C-arm position at the same orbital angle in the forward scan and in the reverse scan completely overlap. A larger overlap enables a "smoother" transition between the image data of the two image volumes of the forward scan and the reverse scan, which were acquired from the same orbital angle. The two image volumes can be merged by interpolation based on the redundant image data.

[0034] Particularly preferably, the value of the maximum lateral offset is determined from the product of the detector width and the difference between the value 1 and the value of the overlap of the X-ray detector in the forward and backward scans at the same orbital angle.

[0035] The value of the maximum lateral offset D is D=12⋅w⋅(1−ol).

[0036] Here, w is the width of the X-ray detector, and ol is the overlap between the two image acquisitions at the two vertices—or, more generally, for an image acquisition with the same orbital angle. As already mentioned, the overlap can be chosen between the values ​​1 and 0.

[0037] The maximum lateral offset D also corresponds to half the distance between the two vertices of the C-arm trajectories of the forward and reverse runs.

[0038] In a preferred embodiment of the method according to the invention for controlling a C-arm of a C-arm system, before the start of the acquisition, the C-arm is shifted from the usual 3D starting position by the required maximum lateral offset lv = -D. During the forward scan between the starting angle of 100° and the AP position with an orbital angle β of 0°, the lateral offset lv remains at lv = -D.

[0039] “AP” is an abbreviation for “anterior-posterior” and describes a frontal image of a patient at a position or orientation or an orbital angle β = 0°, whereby the patient is in a lying position and the connecting line between the X-ray source and the X-ray detector is oriented vertically. The AP point usually also corresponds to the apex point of the respective trajectory for the forward and reverse scan. A starting angle or orbital angle of 100° means that the connecting line between the X-ray source and the X-ray detector is rotated beyond a lateral orientation at the start in order to be able to cover an enlarged angular range during the C-arm scan and thus obtain additional spatial information about the patient examination area to be imaged. With a starting angle of 100°, the examination area to be imaged is figuratively speaking acquired obliquely from below.

[0040] Between an orbital angle of 0°, i.e. the AP point, and an orbital angle of -90°, i.e. a lateral orientation of the connecting line between the X-ray source and the X-ray detector, the lateral offset of the C-arm is reduced to a lateral offset lv = 0 during rotation in the positive lateral direction and remains in the range of the orbital angle of -90° up to the final angle of -100° at a lateral offset lv = 0. During the return, the lateral offset lv remains at the value 0 in the range of an orbital angle of -100° to -90°. Between an orbital angle of -90° and 0°, i.e. between a lateral orientation and an anterior-posterior orientation, the lateral offset lv is increased during rotation in the positive lateral direction to a value lv = +D. Between an orbital angle β of 0° and 100°, the lateral displacement lv remains at a value lv = +D.

[0041] For the forward scan, the focal point of the C-arm X-ray source preferably describes the following trajectory a1: for β > 0°: a1=(SCD⋅sinβ−DSCD⋅cosβ); for -90° < β < 0°: a1=(SCD⋅sinβ−D⋅cosβSCD⋅cosβ); for β < - 90°: a1=(SCD⋅sinβSCD⋅cosβ).

[0042] For the reverse scan, the focal point of the C-arm X-ray source preferably describes the following trajectory a2: for β > 0°: a2=(SCD⋅sinβ+DSCD⋅cosβ); for -90° < β < 0°: a2=(SCD⋅sinβ+D⋅cosβSCD⋅cosβ); for β < - 90°: a2=(SCD⋅sinβSCD⋅cosβ);

[0043] The orbital angle β describes the following curve: β(t)=100°−tT⋅200°,0≤t≤T.

[0044] The SCD value indicates the distance between the X-ray source and the center of the C-arm system, i.e. the center in which the object to be examined or, in particular, the patient is located.

[0045] A reconstruction of 3D image data can be carried out using the projection data recorded according to one of the variants of the method according to the invention with the trajectories a1, a2 according to the invention, as described in DE 10 2020 209 703 A1.

[0046] The invention is explained in more detail below with reference to exemplary embodiments in the accompanying figures. They show: Fig. 1 a schematic representation of a conventional C-arm system, Fig. 2 a schematic representation of a conventional trajectory of a C-arm of a C-arm system, Fig. 3 a schematic representation of a trajectory of a C-arm of a C-arm system according to an embodiment of the invention, Fig. 4 is a flowchart illustrating a method for controlling a C-arm of a C-arm system, Fig. 5 a schematic representation of a control device according to an embodiment of the invention, Fig. 6 is a flowchart illustrating an imaging method for generating 3D image data from an examination object according to an embodiment of the invention.

[0047] In Fig. 1 shows a C-arm system 1 according to a first embodiment of the invention. The C-arm system 1 comprises a C-arm-shaped support element 2, also referred to as C-arm 2 for short, to which at one end of the C-arm 2, which is in Fig. 1 is drawn as the lower end, ie the end facing away from the ceiling DE of a room on which the C-arm system 1 is suspended, an X-ray source 3 is arranged and at the other end of the C-arm 2, which is in Fig. 1 is drawn as the upper end, ie the end facing the ceiling DE, an X-ray detector 4 is arranged.

[0048] A patient couch L is arranged between the X-ray source 3 and the X-ray detector 4, on which a patient O to be examined is positioned. The C-arm 2 is connected by a C-arm suspension 5 to a base 6, which is attached to the ceiling DE. When an image of the patient O is acquired, X-rays are emitted by the X-ray source 3 and detected by the X-ray detector 4 of the C-arm system 1. The acquired measurement signals or the measurement data obtained therefrom are used for image reconstruction.

[0049] In Fig. Figure 2 shows a schematic representation 20 of a conventional trajectory of a C-arm of a C-arm system. A forward and a backward movement are performed, along with additional one-dimensional lateral movements in the rotation plane. The forward movement starts at the starting point SP. v of the forward run, which in Fig. 2 on the right side of the diagram, at an orbital angle β = 100° with a lateral offset lv of -D * cos (100°), where D is the maximum lateral offset. At an orbital angle β = 90°, the lateral offset is lv = 0. Up to an orbital angle β of 0°, a lateral offset lv = -D is continuously built up. Subsequently, the focus reaches the AP point AP vof the forward run, ie the point with the highest y-value, i.e. the vertex of the forward run. Subsequently, the lateral offset lv reduces to a value of 0 up to the orbital angle β = -90°. At the end point EP v During forward travel, the lateral offset lv is again at a value of -D * cos (-100°).

[0050] The focus point of the C-arm is then moved to the starting point SP r of the reverse run. This focus point is located at an orbital angle β = -100°. The lateral offset lv is at a value of +D cos (-100°). At an orbital angle β = -90°, the lateral offset lv is at the value 0. Subsequently, the lateral offset lv increases up to the orbital angle of 0° to the value +D. Subsequently, the AP point AP r, ie the apex of the backward run is reached. After that, the value of the lateral offset lv reduces to 0 up to the orbital angle of 0° and is located at the end point EP r of the reverse run at the value D * cos(100°).

[0051] The Fig. The trajectories shown in Figure 2 place relatively low demands on the mechanical design of a C-arm system 1 and enable large 3D imaging areas even with significantly more cost-effective systems. The endpoint EP v of the forward run does not correspond to the starting point SP rof the reverse scan. Therefore, the system must be moved between scans. This can result in a time delay of several seconds. Since the patient O has to hold their breath during the scan, the time delay should be kept as short as possible. The direction of movement in the lateral direction changes during a scan. In the AP direction (β = 0°), the sign of the speed of the displacement of the focal point in the lateral direction therefore changes. This change can lead to irreproducible geometric inaccuracies, particularly in typical ceiling-suspended systems. Since 3D reconstruction requires very high geometric accuracy when acquiring the X-ray projection data underlying the 3D reconstruction, this can lead to image artifacts.

[0052] For the forward scan, the focal point of the C-arm’s X-ray source describes the following trajectory: a1=(SCD⋅sinβ−D⋅cosβSCD⋅cosβ).

[0053] For the reverse scan, the focal point of the C-arm’s X-ray source describes the following trajectory: a2=(SCD⋅sinβ+D⋅cosβSCD⋅cosβ).

[0054] The orbital angle describes the following curve: β(t)=100°−tT⋅200°,0≤t≤T.

[0055] Half the distance D between the two vertices or AP points AP v, AP r or the maximum offset D is D=12⋅w⋅(1−ol).

[0056] Where w is the width of the X-ray detector and ol is the overlap between the two images at the two vertices or AP points AP v, AP r .

[0057] In Fig. 3 shows a schematic representation 30 of a trajectory of a C-arm of a C-arm system 1 according to an embodiment of the invention.

[0058] Before the start of the acquisition, the C-arm is shifted from the usual 3D starting position by the required lateral offset lv = -D. During forward rotation between the starting angle of 100° and an orbital angle of 0°, the lateral offset lv remains at lv = -D. Between an orbital angle β = 0° and β = -90° during forward rotation, the offset lv is changed from the value -D to the value lv = 0 and remains there within the range of the orbital angle β of -90° up to the final angle of -100°.

[0059] During reverse travel, the lateral offset lv = 0 remains constant within an orbital angle β of -100° to -90°. Subsequently, the lateral offset lv increases between the orbital angle β of -90° and 0° or the AP position AP r of the reverse run to a value of +D. After that, the lateral offset lv is adjusted to the end point EP r of the reverse run is kept constant at its maximum value lv = +D.

[0060] The trajectories a1, a2 of the forward and reverse runs are derived from formulas (2) to (7), which have been described in detail in the general part of the present patent application.

[0061] In Fig. 4 shows a flowchart illustrating a method for controlling a C-arm of a C-arm system 1 according to an embodiment of the invention.

[0062] In step 4.I, the C-arm is moved from the usual centered 3D start position by a lateral offset lv = -D before the start of the acquisition.

[0063] In step 4.II, the lateral offset lv = -D is maintained in the forward run between the starting angle of 100° and the AP position of 0°.

[0064] In step 4.III, the lateral offset lv between the orbital angles β of 0° and -90° is gradually reduced to a value of 0 during rotation in the positive lateral direction.

[0065] In step 4.IV, the lateral offset lv = 0 is maintained in the range of an orbital angle β of -90° to the final angle -100°.

[0066] In step 4.V, the lateral offset of 0 in the backward run is also maintained in the range of an orbital angle β from -100° to - 90°.

[0067] In step 4.VI, the lateral offset lv is gradually increased between an orbital angle β between -90° and 0° during rotation in the positive lateral direction to a value of +D.

[0068] In step 4.VII, the lateral displacement lv is calculated up to the orbital angle β = 100°, i.e. up to the end point EP r of the reverse run at the maximum offset of lv = +D.

[0069] In Fig. Figure 5 shows a schematic representation of a C-arm system 1 with a control device 50 (indicated by dashed lines) according to an embodiment of the invention. In addition to the control device, the C-arm system 1 also includes a C-arm with an X-ray source and an X-ray detector (not shown).

[0070] The control device 50 has a starting unit 51 for controlling a starting position SP v a C-arm 2 in a forward run of a rotation of the C-arm 2 with a lateral offset lv with a first offset value -D and to start the forward run at the start position SP v of the forward run. The start unit 51 is also configured to start a reverse run of a rotation of the C-arm 2 at an end position EP v of the forward run, which also represents the starting position SP r of the reverse run.

[0071] The control device 50 also comprises a rotation unit 52 for rotating the C-arm 2 in the forward direction up to the end position EP v of the forward run, whereby the lateral offset lv is reduced to a value of 0.

[0072] The rotation unit 52 is also designed to move the C-arm 2 in reverse direction to an end position EP r of the reverse run, whereby the lateral offset lv is in the opposite direction of the lateral offset lv of the forward run up to a second offset value +D at the end position EP r of the reverse run is increased.

[0073] During a forward scan and a reverse scan, projection data PD are recorded from an examination object (not shown) by an X-ray detector (not shown) arranged on the C-arm 2.

[0074] Part of the C-arm system 1 is also a reconstruction unit 53, which is configured to reconstruct 3D image data BD based on the projection data PD acquired from an examination object by the X-ray detector of the C-arm 2.

[0075] In Fig. 6 shows a flowchart 600 which illustrates an imaging method for generating 3D image data BD from an examination object 0 according to an embodiment of the invention.

[0076] In step 6.I, projection data PD from the examination object O are acquired by applying the method for controlling a C-arm 2 of a C-arm system 1.

[0077] In step 6.II, 3D image data BD is reconstructed based on the acquired projection data PD.

[0078] Finally, it is emphasized once again that the described C-arm systems are merely preferred embodiments of the invention and that the invention may be varied by those skilled in the art without departing from the scope of the invention, as defined by the claims. For example, for the sake of completeness, it is also noted that the use of the indefinite articles "a" or "an" does not exclude the possibility that the respective features may be present in multiple instances. Likewise, the term "unit" does not exclude the possibility that it may consist of multiple components, which may also be spatially distributed.

[0079] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2020 209 703 A1

[0045]

Claims

[1] Method for controlling a C-arm (2) of a C-arm system (1), comprising the steps: - Carrying out a forward rotation of the C-arm (2), comprising the substeps: - Starting the forward run at a start position (SP v ) of the forward movement of the C-arm (2) with a lateral offset (lv) with a first offset value (-D), - Rotate the C-arm (2) in the forward direction to an end position (EP v ) of the forward run, whereby the lateral offset (lv) is reduced to a value of 0, - Performing a reverse rotation of the C-arm (2), comprising the substeps: - Start reverse at the end position (EP v ) of the forward run, - Rotate the C-arm (2) in the backward direction to an end position (EP r) of the reverse run, whereby the lateral offset (lv) is increased in the opposite direction of the lateral offset (lv) of the forward run up to a second offset value (+D) at the end position (EP r ) of the reverse run. [2] The method according to claim 1, wherein - the starting position (SP v ) of the forward movement of the C-arm (2) has a first angular position, - the final position (EP v ) of the forward run has a second angular position, and - the final position (EP r ) of the reverse run has a third angular position, wherein the first angular position and the second angular position and the third angular position have an angle with the same absolute value. [3] Method according to one of the preceding claims, wherein - the first angular position has an angle of 100°, - the second angular position has an angle of -100°, - the third angular position has an angle of 100°. [4] Method according to one of the preceding claims, wherein the first offset value (-D) and the second offset value (+D) have the same amount (D). [5] Method according to one of the preceding claims, wherein, during the forward run, the rotation of the C-arm (2) in the forward direction comprises the following sub-steps: - Maintain the first offset value (-lv) of the lateral offset (lv) in the forward run between the start position (SP v ) and an AP position (AP v ), - Gradually reducing the lateral offset (lv) between the AP position (AP v ) and a lateral position to the value 0, - Maintain the lateral offset (lv) with the value 0 from the range of the lateral position to the end position (EP v ) of the forward run. [6] Method according to one of the preceding claims, wherein, during the reverse run, the rotation of the C-arm (2) in the reverse direction comprises the following sub-steps: - Maintain the lateral offset (lv) with the value 0 in the range from the end position (EP v ) of the forward run to the lateral position, - Gradually increasing the lateral offset (lv) during rotation in a positive lateral direction between the lateral position and the AP position (AP r ) to a final value (+D), - Maintain the offset (lv) between the AP position (AP r ) and the final position (EP r ) of the reverse run. [7] Method according to one of the preceding claims, wherein the maximum value (D) of the lateral offset (lv) depends on the detector width (w). [8] Method according to one of the preceding claims, wherein the maximum value (D) of the lateral offset (lv) depends on the overlap (ol) of the X-ray detector (4) in the forward run and in the reverse run at the same orbital angles (β). [9] Method according to one of the preceding claims, wherein the maximum value (D) of the lateral offset (lv) is determined on the basis of the product of the detector width (w) and the difference between the value 1 and the value of the overlap (ol) of the X-ray detector (4) in the forward run and in the backward run at the same orbital angle (β). [10] Imaging method for generating 3D image data (BD) of an examination object (O), comprising the steps: - Acquiring projection data (PD) from the examination object (O) by applying the method for controlling a C-arm (2) of a C-arm system (1) according to one of the preceding claims, - Reconstructing 3D image data (BD) based on the acquired projection data (PD). [11] Control device (50), comprising: - a starting unit (51) for - Controlling a starting position (SP v ) of a C-arm (2) in a forward run of a rotation of the C-arm (2) with a lateral offset (lv) with a first offset value (-D) and for starting the forward run at the start position (SP v ) of the forward run and - to start a reverse rotation of the C-arm (2) at an end position (EP v ) of the forward run, - a rotation unit (52) for - Rotate the C-arm (2) in the forward direction until it reaches the end position (EP v ) of the forward run, whereby the lateral offset (lv) is reduced to a value of 0, and - Rotate the C-arm (2) in reverse direction to an end position (EP r) of the reverse run, whereby the lateral offset (lv) is increased in the opposite direction of the lateral offset (lv) of the forward run up to a second offset value (+D) at the end position (EP r ) of the reverse run. [12] C-arm system (1), comprising: - a C-arm (2) which is rotatable or pivotable about at least one rotation or pivot axis, - an X-ray source (3) arranged at a first end of the C-arm (2), - an X-ray detector (4) arranged opposite the X-ray source (3) at a second end of the C-arm (2) for acquiring projection data (PD) from an examination object (O), - a control device (50) according to claim 11, - a reconstruction unit for reconstructing image data based on the acquired projection data (PD). [13] A computer program product comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method according to any one of claims 1 to 10. [14] A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method according to any one of claims 1 to 10.

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