Moment compensation for a C-arm X-ray machine

Abstract

C-arm X-ray device (7) with a C-arm (8) rotatable about an orbital axis (18) perpendicular to the plane of the C-arm within a rotational angle range of up to 190° (± 95°) and pivotable about an angular axis (17) intersecting the orbital axis at right angles within a rotational angle range of up to ± 190°, with an X-ray source (10) and with an X-ray detector (9), wherein the center of gravity (16) of the C-arm (8), X-ray source (10), X-ray detector (9) and additional attachments exerts an internal torque on the C-arm (8) during the orbital movement (14) and a further internal torque during the angular movement (13), characterized in that the internal torques of the orbital movement (14) and the angular movement (13) are each generated by an external torque from the combination of a rotation-angle-dependent lever arm and a rotation-angle-dependent spring force be compensated.

Description

State of the art

[0001] The present invention relates to a system for an external moment compensation for the orbital movement and also for the angular movement of a mobile or stationary C-arm X-ray device for compensating the internal moment of the C-arm X-ray device, which is exerted on the C-arm in the orbital and angular directions by the C-arm, the attachments, the X-ray source and the X-ray detector.

[0002] A mobile C-arm is a medical imaging device based on X-ray technology and designed for flexible use in a clinical setting. Its name derives from the C-shaped arm that rigidly connects the X-ray source (generator) and the X-ray detector (image intensifier or flat-panel detector). This C-shaped connection allows the device to be moved horizontally, vertically, and around its pivot axes, enabling X-ray images of the patient to be acquired from virtually any angle.

[0003] Since the introduction of the first C-arm, the technology has continuously evolved. Particularly interesting, and distinguishing it from conventional C-arms, is the isocentric design, coupled with an optionally switchable motor control for orbital movement and an image processor for 3D reconstruction. In 3D mode, this system enables the acquisition of a defined number of radiographic images at specific angular intervals during automated, continuous orbital rotation around a defined angle, thus allowing for 3D reconstruction. In addition, as a result of technological advancements, stationary and robot-based C-arms have been introduced alongside mobile systems.

[0004] Particularly in C-arms designed in this way, where the central beam of the X-ray system passes through the system's isocenter, which lies on the orbital axis and also represents the axis of rotation of the orbital motion, the overall center of gravity of the arrangement lies radially outside the isocenter to the orbital axis due to the weight distribution. Consequently, the arrangement's own weight exerts a torque on the C-arm, as the center of gravity strives for a stable equilibrium position at the lowest achievable point below the orbital axis. To hold the C-arm in a specific position, a counter-braking torque, or, in the case of movement, a counter-torque against the arrangement's own torque, must be applied. Analogous behavior is also observed during an angular swivel movement.

[0005] The counter-torque was compensated for by additional weights on the C-bend, ensuring that, in every possible position of the assembly, the total torque of the assembly—consisting of its own torque (also known as internal torque) and any counter-torque (also known as external torque)—is balanced. The counter-torque must be of the same magnitude as the torque being compensated for in every position and must act in the opposite direction.

[0006] This approach to moment compensation also applies to the angulation direction, since this compensation should be carried out for both the orbital motion direction and the angulation motion direction.

[0007] The disadvantage of these compensatory measures using additional weights is the increase in the overall weight of the entire system, with additional stress on the C-arm and selected components of the overall system, such as the drive components.

[0008] DE 691 19 904 T2: X-ray examination device

[0009] Patent DE 691 19 904 T2 discloses a C-shaped X-ray examination carrier with a weight compensation system that operates with the aid of two movable counterweights.

[0010] DE 10 2004 011 460 A1: C-arm device with weight compensation

[0011] Patent DE 10 2004 011 460 A1 discloses a compensating device for an X-ray C-arm device for generating a second torque that at least partially compensates the first torque by means of a counterweight coupled to the motion via a gearbox.

[0012] DE 10 2011 004 228 B4: C-arm X-ray unit with weight compensation

[0013] Patent DE 10 2011 004 228 B4 discloses a C-arm X-ray device with a C-arm rotatable about an orbital axis perpendicular to the plane of the C-arm. The external torque, referred to in the patent as the first torque, resulting from the X-ray detector and the X-ray source, is compensated by a second torque from an eccentrically mounted rotatable contour disk that is coupled to the C-arm. The compensating second torque is generated by rotating the contour disk, which is suspended from it by additional masses.

[0014] DE 10 2014 208 345 B4: X-ray device

[0015] Patent DE 10 2014 208 345 B4 discloses a counterweight for an X-ray device in the form of a C-arm frame, at one end of which an X-ray source is arranged and at the other end of which a detector for recording radiation emitted by the X-ray source is arranged. The counterweight is achieved by positioning at least one component of the voltage generator at the same end of the C-arm frame as the detector.

[0016] DE 20 2019 105 029 U1: Omega propulsion unit and medical equipment

[0017] The device described in the utility model has no relation to my patent proposal, as it is an emergency stop device in the event of a belt breakage and not a torque compensation device during operation. In this utility model, the belt drive is achieved via a classic omega drive. A spring-loaded braking device has been integrated for the emergency stop function in the event of a belt breakage. Analogous to so-called slack rope switches or speed limiters, these devices serve to trigger a brake safety device in the event of a rope or belt breakage, for example, in garage doors, elevators, and standard vehicles used in logistics.

[0018] In safety devices – as described in the utility model – only compression springs, not tension springs, should be used. In the event of a spring breakage, tension springs cease to function, while compression springs can generally still perform an emergency function. In this utility model, the function cannot be achieved through frictional engagement because the resulting normal force passes through the pivot point of the circular C-shaped arc and therefore cannot generate a counter-torque or braking torque. However, the counter-torque or braking torque can be generated by the resulting frictional force in the contact area of ​​the mating surfaces. It must be noted that the coefficients of friction can fluctuate considerably during operation due to environmental conditions. A positive-locking force engagement, e.g., in the form of a toothed lock, could effectively implement a counter-torque or braking torque. Purpose and disclosure of the invention

[0019] The present invention is characterized in that a system for moment compensation for both orbital and angular motion is provided for a mobile or stationary C-arm X-ray unit. According to the invention, the stated problem is solved with the C-arm X-ray unit of the independent claim.

[0020] The invention claims a mobile or stationary C-arm X-ray unit with a C-arm that is manually or motor-driven rotatable up to 190° (± 95°) about an orbital axis perpendicular to the plane of the C-arm and up to ± 190° about an angular axis horizontal to the plane of the C-arm and intersecting the orbital axis at right angles. The unit comprises an X-ray source and an X-ray detector, wherein the combined center of gravity of the C-arm, attachments, X-ray source, and X-ray detector exerts an internal torque on the C-arm in both the orbital and angular directions.

[0021] On both the orbital and angular drive shafts, a precisely designed lever arm is integrated into the respective drive shaft for each of the two rotary movements. This lever arm rotates continuously with the drive shaft and, due to its shape, continuously changes its effective lever length during rotation. The lever arm is in contact with a spring system via the end plate. The spring system is fixed to the base plate on the main unit for both the orbital and angular movements and serves to absorb the reaction forces of the respective spring systems. During each rotary movement, the lever arm is in contact with the respective spring system and, at each angular position, generates a corresponding spring force through the deformation of the spring system, thus producing the respective compensation moment for the orbital and angular movements.

[0022] The respective lever arm for compensating the internal torque of the orbital and angular movement has such a shape that the respective acting lever arm in contact with the spring system generates an external angle-dependent torque curve to compensate for the internal torque curve.

[0023] With appropriate design of the contour of the acting lever arm, a rotation angle range of up to 190° (± 95°) can be covered for the orbital axis and a rotation angle range of up to ± 190° for the angular movement. The respective pivot point of the contoured lever arm preferably lies on the respective axis of symmetry of the drive shaft for both the orbital and the angular movements. By slightly shifting the pivot point in the radial coordinate direction with respect to the axis of symmetry of the respective drive shaft, the desired compensation torque profile can be further adjusted. Sinusoidal, cosine, or corresponding modifications and profiles for negative and positive acting torques can be generated with this invention.

[0024] The combination of the effective lever arm length due to contact with the spring system and the resulting spring force generates an external torque that compensates for the internal torque at every angular position of the C-arm X-ray unit. The invention thus offers the advantage that the C-arm remains torque-free in every rotational position with respect to both orbital and angular movement. This results in a primary advantage of weight savings due to the elimination of counterweights, and positive secondary effects from the reduction of stress on the C-arm and selected components of the overall system, such as the drive components. Further secondary effects include the reduction of the dimensions and power consumption of the drive components, such as the drive motors, and their energy requirements.

[0025] To generate the necessary spring forces and spring deflections, classic and well-established technologies from spring engineering are employed. Based on the characteristic variations of spring systems, such as size, spring force profile, number, position, shape, material, surface finish, and type of closure, the required spring system is designed to meet the specific requirements. Example drawing

[0026] The invention is explained in more detail below with reference to schematic drawings. These show: Fig. 1. Schematic representation of the moment compensation system, Fig. Figure 2 schematically shows the parts of the C-arm X-ray unit with the respective connection of the torque compensation system for the orbital and angular movements. The overall assembly with the respective motor drives of the C-arm X-ray unit and the housing unit with its components are not shown.

[0027] Fig. Figure 1 schematically shows the torque compensation system (1) with the contoured lever arm (2). The specifically contoured lever arm (2) is preferably mounted at the center of rotation of the respective drive shaft for the orbital motion (14) and for the angular motion (13) and is coupled to the C-arm (8) for motion. The contoured lever arm (2) is in contact with the head plate (4) via continuous rolling contact and thus with a spring system (5) in the form of a compression spring assembly. The combination of the lever arm, which changes continuously as a result of the rotational motion, and the spring force generated by the simultaneous interaction with the spring system (5) in the form of a compression spring assembly produces an external torque that compensates for the internal torque of the C-arm (8) during the orbital motion (14) and the angular motion (13).The base plate (6) serves as a moment support for connecting the respective moment compensation system to the support structure of the C-arm X-ray unit (7). Due to the different curves of the internal torques, a specific moment compensation system (1) must be designed for each of the following: the compensation of the internal torque of the orbital movement and the compensation of the internal torque of the angular movement. This is achieved by adapting the contoured lever arm (2) and the spring system (5) accordingly.

[0028] Fig.Figure 2 schematically shows the C-arm X-ray unit (7) with the relevant components: C-arm (8), X-ray detector (9), X-ray source (10), drive system for the orbital unit (11), and drive system for the angular unit (12). Additionally, the isocenter (15), the resulting center of gravity of the C-arm system (16), and the axes of rotation for the orbital movement (18) and angular movement (17) are shown. The connections of the torque compensation system to the drive system of the angular unit (20) and of the torque compensation system to the drive system of the orbital unit (19) are also shown schematically. Reference symbol list 1. Moment compensation system 2 Contoured lever arm 3 Drive shaft for orbital or angular movement 4 Head plate 5 spring system 6 Base plate as moment support for connection to the supporting structure of the C-arm X-ray machine 7 C-arm X-ray unit 8 C-arms 9 X-ray detector 10 X-ray source 11 Propulsion system orbital unit 12 Drive system angular unit 13 angular direction of rotation 14 orbital direction of rotation 15 Isocenter 16 Focus 17 Angulation axis 18 Orbital axis 19 Moment compensation for orbital motion 20 Moment compensation for the angular movement

Claims

[1] C-arm X-ray unit (7) with a C-arm (8) rotatable about an orbital axis (18) perpendicular to the plane of the C-arm within a rotational angular range of up to 190° (± 95°) and also pivotable about an angular axis (17) intersecting the orbital axis at right angles within a rotational angular range of up to ± 190°, with an X-ray source (10) and with an X-ray detector (9), wherein the center of gravity (16) of the C-arm (8), X-ray source (10), X-ray detector (9) and additional attachments exerts an internal torque on the C-arm (8) during the orbital movement (14) and another internal torque during the angular movement (13), characterized by , that the internal torques of the orbital motion (14) and the angular motion (13) are each compensated by an externally generated torque from the combination of rotation angle-dependent lever arm and rotation angle-dependent spring force. [2] C-arm X-ray unit (7) according to claim 1 characterized by, that a lever arm (2) preferably mounted at the center of rotation of the drive shaft of the orbital motion (14) and specifically contoured, which is coupled to the C-arm (8) in motion, is in continuous rolling contact via a head plate (4) with a spring system (5) and, through the combination of the lever arm (2) which changes continuously as a result of the rotational motion and the spring force generated by the simultaneous interaction with the spring system (5), generates an external torque compensating the internal torque during the orbital motion (14). [3] C-arm X-ray device (7) according to claim 2, characterized by, that when the C-arc (8) is rotated about the orbital axis (18), the specifically contoured lever arm (2) for the orbital movement (14) rotates in such a way that the interaction of the contoured lever arm (2) with the spring system (5) in contact via the head plate (4) generates an external torque that compensates for the internal torque of the orbital movement (14) for each angle of rotation. [4] C-arm X-ray unit (7) according to claim 1 characterized by, that a lever arm (2) preferably mounted at the center of rotation (17) of the drive shaft of the angular movement (13) and specifically contoured, which is coupled to the movement of the C-arm (8), is in continuous rolling contact via a head plate (4) with a spring system (5) and, through the combination of the lever arm (2) which changes continuously as a result of the rotational movement and the spring force generated by the simultaneous interaction with the spring system (5), generates an external torque compensating the internal torque during the angular movement (13). [5] C-arm X-ray device (7) according to claim 4, characterized by, that when the C-bow (8) is rotated about the angular axis (17), the specifically contoured lever arm (2) for the angular movement (13) rotates in such a way that the interaction of the contoured lever arm (2) with the spring system (5) in contact via the head plate (4) generates an external torque that compensates for the internal torque of the angular movement (13) for each rotation angle position.

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