Track of C-arm of C-arm system

Abstract

The invention relates to a method for controlling a C-arm (2) of a C-arm system (1). In the method for controlling a C-arm (2) of a C-arm system (1), a forward operation of rotation of the C-arm (2) is carried out. According to the invention, the forward operation is initiated at a starting position (SPv) of the forward operation of the C-arm with a lateral offset (lv) having a first offset value (-D), and the C-arm (2) is rotated in the forward direction up to an end position (EPv) of the forward operation, the lateral offset (lv) decreasing to a value 0. In addition, a reverse operation of the rotation of the C-arm (2) is carried out. According to the invention, the C-arm (2) is rotated in the forward direction, the reverse direction is started in an end position (EPv) of the forward direction, and the C-arm (2) is rotated in the reverse direction up to an end position (EPr) of the reverse direction, the lateral offset (lv) increasing in the opposite direction of the lateral offset (lv) of the forward direction up to a second offset value (+ D) at the end position (EPr) of the reverse direction. Furthermore, an imaging method for generating 3D image data (BD) of an examination object (O) is described. A control device (50) is also described. The invention further relates to a C-arm system (1).

Description

Technical Field

[0001] The invention relates to a method for controlling a C-arm of a C-arm system. In the method, a forward rotation of the C-arm and a reverse rotation of the C-arm are performed. The invention also relates to an imaging method for generating 3D image data of an examination object. In addition, the invention also relates to a control device. In addition, the invention also relates to a C-arm system. Background Art

[0002] Modern imaging methods generate two-dimensional or three-dimensional image data which can be used for visualizing the imaged examination object and also for other applications.

[0003] Imaging methods are usually based on detecting X-rays. X-ray systems usually include an X-ray source and an X-ray detector opposite the X-ray source. During imaging, the object to be examined, especially a patient, is positioned in the gap between the X-ray source and the X-ray detector, and an image of the object to be examined is taken. 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, which is usually a flat detector, are fixed on a C-shaped support element, also called a C-arm. Due to its shape, the C-arm and the corresponding diagnostic or therapeutic device or X-ray detector can be moved in an orbit around the point of the patient to be examined or treated, so as to achieve different angular positions between the patient and the diagnostic or therapeutic device or the X-ray detector without moving the patient.

[0004] If the local area to be examined or treated is to be imaged from different positions or if the imaging system or the X-ray detector is to be moved together when imaging a larger area of ​​the examination object, the C-arm is rotated, for example, about a support axis centrally connected to the center of the C-arm.

[0005] In the field of interventional therapy, there is already technology for 3D imaging with the help of C-arm angiography devices. However, compared with traditional CT systems, there is a clear limitation in that the size of the flat detector limits the imaging area. The limited imaging area makes it impossible to detect many organs, such as the lungs and liver, by a single shot. In addition, the projection data of almost all body regions are cut off or truncated laterally, which leads to image artifacts (truncation artifacts) in common reconstruction methods.

[0006] The C-arm 3D imaging solutions with large imaging areas used clinically so far assume that the relative position of the focus (i.e. the point where the electrons hit the anode of the X-ray source or the point where the X-ray photons are emitted) relative to the measurement object (patient) remains constant. In the existing "large volume" solutions of robotic systems, the focus moves around the patient in a circular trajectory. The distance to the patient therefore remains constant. For angiography systems with a rigid C-arm, this requires that the isocenter of the C-arm be dynamically translated laterally in both directions in the rotation plane during the rotation around the patient, which is only possible with complex robotic mechanics.

[0007] For classic isocentric angiography systems, a trajectory of the isocenter with a transverse translation is used. In this case, forward and reverse motions are performed in the rotation plane and an additional one-dimensional transverse motion is performed at the same time. Figure 1 The shown trajectory places much lower demands on the mechanical design of the C-arm system and enables a large 3D imaging range even with a simply constructed C-arm system. Figure 1 The trajectories shown still suffer from practical drawbacks:

[0008] - The end point of the forward run does not coincide with the start point of the reverse run. Therefore, the system must be moved between runs. This can result in a time delay of several seconds. Since the patient must hold his breath during the recording, the time delay should be as short as possible.

[0009] - During operation, the direction of the movement in the transverse direction changes. As a result, the sign of the velocity in the transverse direction changes in the AP direction (AP is the acronym for "anterior-posterior"). This change can lead to non-reproducible geometric errors, especially in typical ceiling-mounted systems. Since 3D reconstruction requires a very high accuracy of the acquisition geometry, this can lead to image artifacts. Summary of the invention

[0010] The object of the present invention is therefore to provide a method and a control device for controlling a C-arm, by means of which imaging can be performed in a time-saving manner with reduced image artifacts.

[0011] The technical object is achieved by a method for controlling a C-arm of a C-arm system, an imaging method for generating 3D image data of an examination object, a control device and a C-arm system.

[0012] In the method for controlling a C-arm system, preferably a C-arm of a top-suspended C-arm system according to the present invention, a forward movement of the rotation of the C-arm is performed as described in the opening. The forward movement is started at the starting position of the forward movement of the C-arm with a lateral offset having a first offset value. The lateral offset should be understood as a translation of the C-arm along a horizontal direction transverse to the patient's couch. As a result, the focus of the X-ray source of the C-arm system is also translated along the lateral direction. The C-arm is then rotated in the forward direction to the end position of the forward movement, wherein the lateral offset decreases monotonically to 0. In addition to the above-mentioned value of 0 for the offset, the end point of the forward movement also has a predetermined value of the orbit angle β. As will be described in detail later, the values ​​of the orbit angles of the starting point and the end point are selected so that the imaging can cover a sufficiently large angle range around the examination object. The values ​​of the orbit angle β of the starting point and the end point of the forward movement are preferably at least 90° or -90°, respectively. The values ​​of the orbit angle β of the starting point and the end point of the forward movement are preferably 100° or -100°, respectively. It is also preferred that the values ​​of the orbit angle β of the start and end points of the forward run are preferably in the interval [90°, 120°] or [-90°, -120°]. For mechanical reasons, in particular, overhead suspended systems cannot be moved at any angle. It is also possible to shift the start / end angle (from the ideal value = 100°) to 20°, further shifting will generally make the system unable to rotate mechanically.

[0013] Also as mentioned at the beginning, the C-arm is then rotated in the reverse direction, i.e., in the direction opposite to the forward direction. The reverse operation is first started at the end position of the forward operation, and the C-arm is then rotated in the reverse direction to the end position of the reverse operation. During the rotation, the lateral offset increases monotonically in the direction opposite to the lateral offset of the forward operation until a second offset value is reached at the end position of the reverse operation. "Increase" should mean an increase in the absolute value of the lateral offset. For example, if the lateral offset during the forward operation is positive, the lateral offset during the reverse operation is negative. If the lateral offset during the forward operation is negative, the lateral offset during the reverse operation is positive. Advantageously, the trajectories of the forward operation and the reverse operation are different, so that additional image information of the patient can be obtained during the reverse operation.

[0014] Unlike conventional control methods, in the method according to the invention, the end point of the forward run corresponds to the start point of the reverse run. Advantageously, the C-arm does not need to be moved between the forward run and the reverse run. Since the patient must hold his breath during the recording, the time delay between the forward run and the reverse run is advantageously avoided or kept as short as possible.

[0015] Furthermore, it is advantageously achieved that the direction of the movement of the C-arm in the transverse direction does not change during operation, ie during forward operation and during reverse operation.

[0016] Especially in typical overhead systems, such changes in the direction of movement during operation can lead to geometric errors that cannot be reproduced in conventional methods. Since 3D reconstruction requires very high geometric accuracy of the acquisition, these errors can lead to image artifacts. Since the direction of movement during the lateral movement of the C-arm remains within the forward and reverse movement sequence, such image artifacts are now advantageously avoided.

[0017] In the imaging method according to the invention for generating 3D image data of an examination object, projection data of the examination object are detected by using a method for controlling a C-arm of a C-arm system, and 3D image data are reconstructed based on the detected projection data. Advantageously, 3D image data of an examination object, preferably a patient, with improved quality can be acquired by the imaging method according to the invention.

[0018] The control device according to the present invention has a starting unit, which is used to control the starting position of the C-arm with a lateral offset having a first offset value in the forward operation of the C-arm rotation, and to start the forward operation in the starting position of the forward operation, and to start the reverse operation of the rotation of the C-arm at the end position of the forward operation.

[0019] The control device according to the invention further comprises a rotation unit for rotating the C-arm in the forward operation in the forward direction to the end position of the forward operation, wherein the lateral offset is reduced to a value of 0, and for rotating the C-arm in the reverse operation in the reverse direction to the end position of the reverse operation, wherein the lateral offset is increased in a direction opposite to the lateral offset in the forward operation to a second offset value at the end position of the reverse operation. The control device according to the invention has the same advantages as the method according to the invention for controlling a C-arm of a C-arm system.

[0020] The C-arm system according to the invention comprises a C-arm, preferably a C-arm-shaped support element, which can be rotated or pivoted about at least one rotation or pivot axis. The C-arm system according to the invention also comprises an X-ray source and an X-ray detector, the X-ray source being arranged at a first end of the C-arm, preferably a C-arm-shaped support element, and the X-ray detector being arranged at a second end of the C-arm opposite the X-ray source. The C-arm system according to the invention also comprises a control device according to the invention. The C-arm system according to the invention has the same advantages as the method according to the invention for controlling a C-arm of a C-arm system.

[0021] Most of the above-mentioned components of the control device and the C-arm system can be implemented completely or partially in the form of software modules in the processor of the corresponding computing system. A largely software-based implementation has the advantage that the computing systems that are currently already in use can also be converted in a simple manner by software updates so as to work in the manner according to the invention. In this regard, the technical problem is solved by a corresponding computer program product with a computer program, which can be directly loaded into the computing system as program sections, and when the program is executed in the computing system, the program sections can execute the steps of the method according to the invention for controlling the C-arm of the C-arm system. In addition to the computer program, such a computer program product can optionally include additional components, such as documentation and / or additional components, as well as hardware components, such as hardware keys (dongles, etc.) for the use of the software.

[0022] A computer-readable medium, such as a memory stick, a hard disk or other removable or fixedly mounted data carrier, on which program sections of a computer program are stored that can be read and executed by a computing system can be used for transmission to a computing system or a control device and / or for storage in or at a computing system or a control device. For this purpose, a computing system can, for example, have one or more cooperating microprocessors or similar devices.

[0023] The following description contains particularly advantageous designs and extended designs of the present invention. In particular, multiple claims of one claim category can also be improved similarly to the dependent claims of another claim category. In addition, different technical features of different embodiments and claims can also be combined into new embodiments within the scope of the present invention.

[0024] In one embodiment of the method for controlling a C-arm of a C-arm system according to the present invention, the starting position of the forward operation of the C-arm has a first angular position. In addition, the end position of the forward operation has a second angular position, and the end position of the reverse operation has a third angular position. The first angular position, the second angular position and the third angular position preferably have angles with the same absolute value. Advantageously, the angular ranges through which the C-arm and therefore the X-ray detector and the X-ray source move in the forward operation and the reverse operation are symmetrical. A patient who is located on a patient couch that is symmetrical with respect to the AP position (anteroposterior position, the patient is irradiated in the vertical direction, and the orbit angle is 0°) can advantageously be imaged from both sides at angles with the same absolute value.

[0025] In order to obtain sufficient data for a 3D reconstruction, at least one circular arc segment of 200° must be moved. It is expedient here to rotate along a circular arc segment of 100° in each case "to the left" and "to the right" of the AP plane. For mechanical reasons, especially ceiling-mounted systems cannot be moved by any angle. It is also possible to shift the start / end angle by up to 20°, further shifting would make it impossible to mechanically rotate the system.

[0026] The first angular position preferably has an angle of 100°, the second angular position preferably has an angle of -100°, and the third angular position preferably has an angle of 100°. Image data can advantageously be acquired over an angular range of 200°, so that the examination region or the examination object can be imaged from different directions. Image information detected from different directions can advantageously be combined into a 3D image of the examination region.

[0027] Therefore, preferably an orbit angle of 100 ° is used as the starting position for the forward run, and preferably an orbit angle of -100 ° is used as the end position for the forward run. In addition, an orbit angle of -100 ° is used as the starting position for the reverse run, and an orbit angle of 100 ° is used as the end position for the reverse run.

[0028] As mentioned above, for forward and reverse operation, an angular range of at least 200° should preferably be shifted. The angular range shifted should also preferably be in a value range between 180° and 240°, particularly preferably between 190° and 210°.

[0029] The first offset value and the second offset value particularly preferably have the same absolute value. Since the patient is usually approximately symmetrical with respect to the sagittal plane, it is reasonable to use an offset that is equal in both directions.

[0030] In another particularly preferred variant of the method according to the invention for controlling a C-arm of a C-arm system, during forward operation, the rotation of the C-arm in the forward direction comprises the following steps:

[0031] - a first offset value for maintaining the lateral offset in the forward run between the start position and the AP position,

[0032] - the lateral offset decreases gradually to a value of 0 between the AP position and the lateral position,

[0033] - Keep the lateral offset value at 0 from the lateral position to the end position of the forward run.

[0034] The first offset value for the lateral offset at the start of the forward operation is advantageously reduced continuously down to the lateral position, so that a uniform imaging is achieved.

[0035] Alternatively, during forward travel, the deflection is not reduced to 0 in the transverse position, but only in the end position. Advantageously, a continuous change of the deflection up to the end position is achieved.

[0036] In the reverse operation, the rotation of the C-arm in the reverse direction preferably includes:

[0037] - Keep the lateral offset value at 0 from the end position of the forward run to the lateral position,

[0038] - during the rotation, the lateral offset gradually increases in the positive lateral direction between the lateral position and the AP position to a terminal value, wherein the lateral offset is in the opposite direction relative to the lateral offset of the forward run,

[0039] - Maintaining the offset between the AP position and the end position of the reverse run.

[0040] Advantageously, no deflection changes occur in the "right" quadrant, i.e. in the forward and reverse directions. This is because any deflection changes that occur in the right quadrant must be compensated by a movement in the left quadrant in the opposite direction. If deflection changes occur in both directions during movement, the disadvantages described above arise, i.e. a change in direction of movement in the transverse direction during operation, such as Figure 2 This is the case with the conventional trajectory shown. It is therefore advantageous to determine the offset in one direction before starting the rotation so that in the right quadrant the offset does not change during the rotation and on the return the offset remains unchanged until the end.

[0041] In another preferred variant of the method for controlling a C-arm of a C-arm system according to the invention, the maximum value of the lateral offset depends on the detector width. The maximum lateral offset should be selected so that images taken from the same angle in the forward run and the reverse run can be connected. If the same value but with opposite signs is selected as the maximum lateral offset in the forward run and the reverse run, the offset should be a maximum of half the detector width. If the maximum lateral offset is smaller, an overlapping area is generated between the image data taken at the same orbital angle in the forward run and the reverse run. Adjacent image acquisitions can advantageously be combined more easily due to the overlap.

[0042] It is also preferred that in the method according to the invention for controlling a C-arm of a C-arm system, the maximum value of the lateral offset preferably depends on the overlap of the X-ray detectors in the forward run and in the reverse run. The overlap can have a value from 0 to 1. The value "0" here means that there is no overlap, and the value "1" means that the images captured in the forward run and in the reverse run with the same orbital angle completely overlap. The greater the overlap, the more "smooth" the transition between the image data of the two image populations in the forward run and in the reverse run. The two image populations can be combined by interpolation based on redundant image data.

[0043] The value of the maximum lateral offset is preferably determined by the product of the detector width and the difference between the value of the overlap of the x-ray detectors in forward travel and reverse travel at the same orbital angle and the value 1.

[0044] The value of the maximum lateral displacement D is here

[0045]

[0046] Here, w is the width of the X-ray detector and ol is the overlap of two image recordings at two vertices or, in general, the overlap of image recordings at the same orbit angle. As already mentioned, the overlap can be selected between 1 and 0.

[0047] The maximum lateral deviation D also corresponds to half the distance between the two vertices of the C-arm trajectory in the forward and reverse directions.

[0048] In a preferred embodiment of the method according to the invention for controlling a C-arm of a C-arm system, the C-arm is deflected from the usual 3D starting position by the necessary maximum lateral offset lv=-D before the start of the acquisition. In the forward run between the starting angle 100° and the AP position with an orbit angle β of 0°, the lateral offset lv remains at lv=-D.

[0049] "AP" is the abbreviation for "anterior-posterior" and describes the image recording of the front side of the patient at a position or orientation or orbit angle β=0°, wherein the patient is in a recumbent position and the connecting line between the X-ray source and the X-ray detector is oriented vertically. In the forward and reverse operation, the AP point usually also corresponds to the vertex of the corresponding trajectory. A starting angle or orbit angle of 100° means that the connecting line between the X-ray source and the X-ray detector is rotated beyond the transverse orientation at the start in order to be able to move through a larger angular range during the C-arm recording and thus obtain additional spatial information about the patient's examination area to be imaged. At a starting angle of 100°, the examination area to be imaged is recorded, figuratively speaking, from obliquely below.

[0050] Between an orbital angle of 0°, i.e. an orientation transverse to the AP point, and an orbital angle of -90°, i.e. an orientation transverse to the line between the X-ray source and the X-ray detector, the lateral offset of the C-arm decreases during the rotation in the positive lateral direction to a lateral offset lv=0, and maintains the lateral offset lv=0 in the range from an orbital angle of -90° to a terminal angle of -100°. In the return, the lateral offset lv remains at 0 in the range of orbital angles from -100° to -90°. Between orbital angles of -90° and 0°, i.e. between the transverse orientation and the anterior-posterior orientation, during the rotation, the lateral offset lv increases in the positive lateral direction to a value lv=+D. Between orbital angles β of 0° and 100°, the lateral offset lv remains at a value lv=+D.

[0051] For the forward run, the focal point of the X-ray source of the C-arm preferably describes the following trajectory a1:

[0052] For β>0°:

[0053]

[0054] For -90°<β<0°:

[0055]

[0056] For β < -90°:

[0057]

[0058] For the reverse run, the focal point of the X-ray source of the C-arm preferably describes the following trajectory a2:

[0059] For β>0°:

[0060]

[0061] For -90°<β<0°:

[0062]

[0063] For β < -90°:

[0064]

[0065] The orbital angle β describes the following curve:

[0066]

[0067] The value SCD indicates the distance between the X-ray source and the center of the C-arm system, ie, the center where the examination object or, in particular, the patient is located.

[0068] As described in DE 10 2020209703 A1, 3D image data can be reconstructed according to one of the variants of the method according to the invention using the projection data recorded according to the trajectories a1 , a2 according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] The present invention will be explained in more detail below with reference to the accompanying drawings with the aid of embodiments. In the accompanying drawings:

[0070] Figure 1 shows a schematic diagram of a conventional C-arm system,

[0071] Figure 2 A schematic diagram showing a conventional trajectory of a C-arm of a C-arm system,

[0072] Figure 3 FIG. 4 shows a schematic diagram of the trajectory of a C-arm of a C-arm system according to an embodiment of the present invention,

[0073] Figure 4 A flow chart is shown which illustrates a flow chart of a method for controlling a C-arm of a C-arm system,

[0074] Figure 5 A schematic diagram showing a control device according to an embodiment of the present invention is shown,

[0075] Figure 6 A flow chart is shown which illustrates an imaging method for generating 3D image data of an examination object according to one exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0076] Figure 1 1 shows a C-arm system 1 according to a first embodiment of the present invention. The C-arm system 1 comprises a C-arm-shaped support element 2, also referred to as C-arm 2 for short, wherein an X-ray source 3 is arranged at one end of the C-arm 2. Figure 1 The X-ray detector 4 is arranged at the other end of the C-arm 2, which is shown as the lower end, that is, the end away from the top DE of the space where the C-arm system 1 is suspended. Figure 1 The upper end, ie the end toward the top DE, is shown in FIG.

[0077] The patient couch L is located between the X-ray source 3 and the X-ray detector 4, and the patient O to be examined is arranged on the patient couch. The C-arm 2 is connected to the base 6 by the C-arm suspension device 5, and the base 6 is fixed at the top DE. When the patient O is imaged, X-rays are emitted from the X-ray source 3 and detected by the X-ray detector 4 of the C-arm system 1. The detected measurement signals or the measurement data obtained therefrom are used for image reconstruction.

[0078] Figure 2A schematic diagram 20 of a conventional trajectory of a C-arm of a C-arm system is shown. In this case, forward and reverse motions are performed in the rotation plane and an additional one-dimensional transverse motion is performed. Forward motion At the starting point SP of the forward motion v Starting at Figure 2 As shown on the right, where the orbit angle β = 100°, the lateral offset lv is -D*cos(100°), where D is the maximum lateral offset. When the orbit angle β = 90°, the lateral offset lv = 0. Until the orbit angle β is 0°, the lateral offset lv = -D is continuously formed. The focus then reaches the AP point AP in the forward direction. v , which is the point with the largest y value, and is also the vertex of the forward run. The lateral offset lv then decreases until it decreases to 0 when the orbit angle β = -90°. At the end point EP of the forward run v At , the value of the lateral offset lv is again -D*cos(-100°).

[0079] The focus of the C-arm then moves to the starting point SP of the reverse run. r . This focus is located at an orbital angle β = -100°. The value of the lateral offset lv is +Dcos(-100°). In the case of an orbital angle β = -90°, the value of the lateral offset lv is 0. The lateral offset lv then increases until it reaches the value +D at an orbital angle of 0°. Then the AP point AP is reached r , which is the apex of the reverse run. Thereafter, the value of the lateral displacement lv decreases until it decreases to 0 when the orbit angle is 0°, and at the end point EP of the reverse run r The value is D*cos(100°).

[0080] Figure 2 The trajectory shown places relatively low demands on the mechanical design of the C-arm system 1 and enables a large 3D imaging range even at significantly lower cost. v The starting point SP of the reverse run r Inconsistency. Therefore, the system has to be moved between runs. This can result in a time delay of several seconds. Since the patient O has to hold his breath during the recording, the time delay should be as short as possible. During the run, the direction of the movement in the lateral direction changes. Therefore, for the AP direction (β=0°), the sign of the speed of the displacement of the focus in the lateral direction changes. This change can lead to non-reproducible geometric errors, especially in typical ceiling-suspended systems. Since 3D reconstruction requires very high geometric accuracy when detecting the X-ray projection data on which the 3D reconstruction is based, this can lead to image artifacts.

[0081] For the forward run, the focal point of the X-ray source of the C-arm describes the following trajectory:

[0082]

[0083] For the reverse run, the focal point of the X-ray source of the C-arm describes the following trajectory:

[0084]

[0085] The orbit angle describes the following curve:

[0086]

[0087] Two vertices or AP points AP v 、AP r Half of the distance D between them or the maximum offset D is

[0088]

[0089] Here, w is the width of the X-ray detector and ol is the distance between the two vertices or AP points. v 、AP r The overlap between the two image shots.

[0090] Figure 3 A schematic diagram 30 of the trajectory of a C-arm of a C-arm system 1 according to an embodiment of the present invention is shown.

[0091] Here, before starting the acquisition, the C-arm is translated from the usual 3D starting position by the necessary lateral offset lv=-D. In the forward run between a starting angle of 100° and an orbit angle of 0°, the lateral offset lv remains at lv=-D. During the rotation in the forward direction between orbit angles β=0° and β=-90°, the offset lv changes from the value -D to the value lv=0 and remains unchanged in the range from an orbit angle β of -90° to an end angle of -100°.

[0092] During reverse operation, the lateral offset lv=0 is maintained in the range of orbit angle β from -100° to -90°. Then, between orbit angle β of -90° and 0° or between orbit angle β of -90° and AP position AP of reverse operation r The lateral displacement lv increases to a value of +D. Thereafter, the lateral displacement lv remains constant at its maximum value lv = +D until the end point EP of the reverse run. r .

[0093] The trajectories a1, a2 for the forward and reverse running directions are obtained from the formulas (2) to (7), which are described in detail in the general part of this patent application.

[0094] Figure 4A flow chart is shown which illustrates a method for controlling a C-arm of a C-arm system 1 according to one exemplary embodiment of the present invention.

[0095] In step 4.I, the C-arm is translated from a usual centrally located 3D starting position by a lateral offset lv=-D before the acquisition starts.

[0096] 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°.

[0097] In step 4.III, between orbit angles β of 0° and −90°, the lateral offset lv is gradually reduced during the rotation in the positive lateral direction to a value of 0.

[0098] In step 4.IV, the lateral offset lv=0 is maintained in the range from a track angle β of −90° to a stop angle of −100°.

[0099] In step 4.V, a lateral offset of 0 is likewise maintained in the reverse run within the range of an orbit angle β of −100° to −90°.

[0100] In step 4.VI, between orbit angles β of 0° and −90°, the lateral offset lv is gradually increased during the rotation along the positive lateral direction to a value +D.

[0101] In step 4.VII, the lateral offset lv is maintained until the track angle β = 100°, i.e. the end point EP of the reverse run at the maximum offset lv = +D r .

[0102] Figure 5 A schematic diagram of a C-arm system 1 with a control device 50 (marked with dashed lines) according to an embodiment of the present invention is shown. 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).

[0103] The control device 50 has a start unit 51 for controlling the starting position SP of the C-arm 2 with a lateral offset lv having a first offset value −D during the forward rotation of the C-arm 2 . v , and for the starting position SP in the forward direction v The starting unit 51 is also configured to start the forward operation at the end position EP of the forward operation. v The reverse rotation of the C-arm 2 is started in the middle, and the end position is also the starting position SP of the reverse rotation. r .

[0104] The control device 50 further comprises a rotation unit 52, which is used to rotate the C-arm 2 in the forward operation along the forward direction until the end position EP of the forward operation. v , where the lateral offset lv is reduced to the value 0.

[0105] The rotation unit 52 is also configured to rotate the C-arm 2 in the reverse direction during the reverse operation until the end position EP of the reverse operation is reached. r , wherein the lateral displacement lv increases in the opposite direction of the lateral displacement lv of the forward run until the end position EP of the reverse run r The offset value is increased to the second offset value +D.

[0106] During the forward and reverse operation, projection data PD from an examination object (not shown) are detected by an X-ray detector (not shown) arranged at the C-arm 2 .

[0107] A reconstruction unit 53 is also part of the C-arm system 1 , which is provided for reconstructing 3D image data BD based on projection data PD of the examination object detected by the X-ray detector of the C-arm 2 .

[0108] Figure 6 A flow chart 600 is shown which illustrates an imaging method for generating 3D image data BD of an object under examination O according to one exemplary embodiment of the present invention.

[0109] In step 6 .I, projection data PD of the examination object O are detected using the method for controlling the C-arm 2 of the C-arm system 1 .

[0110] In step 6.II, 3D image data BD are reconstructed based on the detected projection data PD.

[0111] Finally, it should be made clear that the C-arm described above is only a preferred embodiment of the invention and that the invention can be modified by a person skilled in the art without departing from the scope of protection of the invention given by the claims. For the sake of completeness, it should also be pointed out that the use of the indefinite article "a" does not exclude that the relevant feature may be present in multiple numbers. Similarly, the term "unit" does not exclude that it is composed of multiple components, which may also be spatially distributed if necessary.

[0112] Regardless of the grammatical gender of a particular term, persons with either male or female gender identities are included.

Claims

1. A method for controlling a C-arm (2) of a C-arm system (1), the method comprising the following steps: - performing a forward rotation of the C-arm (2), the forward rotation comprising the following sub-steps: - at a starting position (SP) of the forward movement of the C-arm (2) with a lateral offset (lv) having a first offset value (-D) v ) starts forward operation, - Rotate the C-arm (2) in the forward direction until the end position (EP) of the forward movement v ),in, The lateral offset (lv) is reduced to a value of 0, - performing a reverse rotation of the C-arm (2), the reverse rotation comprising the following sub-steps: - At the end position (EP v ) starts reverse operation, - Rotate the C-arm (2) in the reverse direction until the end position of the reverse motion (EP r ), wherein the lateral displacement (lv) increases in the opposite direction of the lateral displacement (lv) of the forward run until the end position (EP) of the reverse run r ) is increased to the second offset value (+D).

2. The method according to claim 1, wherein: - the starting position (SP) of the forward movement of the C-arm (2) v ) has a first angular position, - The end position of the forward run (EP v ) has a second angular position, and - The end position of the reverse run (EP r ) has a third angular position, The first angular position, the second angular position and the third angular position have angles with the same absolute value.

3. The method according to any one of the preceding claims, - the first angular position has an angle of 100°, - said second angular position has an angle of -100°, - said third angular position has an angle of 100°.

4. A method according to any one of the preceding claims, wherein: The first offset value (-D) and the second offset value (+D) have the same absolute value (D).

5. A method according to any one of the preceding claims, wherein: In the forward operation, the rotation of the C-arm (2) along the forward direction comprises the following sub-steps: - In the starting position (SP v ) and AP location (AP v ) in the forward run between the first offset value (-lv) of the lateral offset (lv), - The lateral offset (lv) at the AP position (AP v ) and the horizontal position gradually decreases to 0, - From the lateral position to the end position of the forward run (EP v ) keeps the value of the lateral offset (lv) at 0.

6. A method according to any one of the preceding claims, wherein: In the reverse operation, the rotation of the C-arm (2) in the reverse direction comprises the following sub-steps: - At the end position (EP v ) to the horizontal position, keep the horizontal offset (lv) value at 0. - During rotation, the lateral offset (lv) is between the lateral position and the AP position (AP r ) and gradually increases along the positive lateral direction to the terminal value (+D), -At the AP location (AP r ) and the end position of reverse operation (EP r ) maintain the offset (lv) between.

7. A method according to any one of the preceding claims, wherein: The maximum value (D) of the lateral offset (lv) depends on the detector width (w).

8. A method according to any one of the preceding claims, wherein: The maximum value (D) of the lateral deviation (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 angle (β).

9. A method according to any one of the preceding claims, wherein: The maximum value (D) of the lateral deviation (lv) is determined based on the product of the detector width (w) and the difference between the value of the overlap (ol) of the X-ray detector (4) in forward operation and reverse operation with the same orbital angle (β) and the value 1.

10. An imaging method for generating 3D image data (BD) of an object under examination (O), the method comprising the following steps: - detecting projection data (PD) of the examination object (O) by using the method for controlling a C-arm (2) of a C-arm system (1) according to any of the preceding claims, - Reconstructing 3D image data (BD) based on the detected projection data (PD).

11. A control device (50), comprising: - a starting unit (51) for - in the forward direction of rotation of the C-arm (2), controlling the starting position (SP) of the C-arm (2) with a lateral offset (lv) having a first offset value (-D) v ) and is used at the starting position (SP v ) starts forward operation, and - At the end position of forward operation (EP v ) starts the reverse rotation of the C-arm (2), - a rotating unit (52) for - Rotate the C-arm (2) in the forward direction until the end position (EP) of the forward movement v ),in, The lateral deviation (lv) decreases to a value of 0, and - In the reverse direction, rotate the C-arm (2) until the end position (EP r ), wherein the lateral displacement (lv) increases in the opposite direction of the lateral displacement (lv) of the forward run until the end position (EP) of the reverse run r ) is increased to the second offset value (+D).

12. A 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), which is arranged at the second end of the C-arm (2) opposite the X-ray source (3) and is used to detect projection data (PD) of the examination object (O), - A control device (50) according to claim 11, - a reconstruction unit for reconstructing image data based on the detected projection data (PD).

13. A computer program product comprising instructions which, when the program is 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 implement the steps of the method according to any one of claims 1 to 10.

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