WO2016124384A1

WO2016124384A1 - Device for controlling a movement of an object and a c-arm of an imaging system

Info

Publication number: WO2016124384A1
Application number: PCT/EP2016/050936
Authority: WO
Inventors: John Allan BRACKEN; Monica TAVANTI
Original assignee: Koninklijke Philips NV
Current assignee: Koninklijke Philips NV
Priority date: 2015-02-02
Filing date: 2016-01-19
Publication date: 2016-08-11
Anticipated expiration: 2017-08-02

Abstract

The invention relates to a device (10) for controlling a movement of an object and a C-arm (24) of an imaging system (1) relative to each other, an imaging system (1), a method for controlling a movement of an object and a C-arm (24) of an imaging system (1) relative to each other, a computer program element for controlling such device (10) or system for performing such method and a computer readable medium having stored such computer program element. The device (10) comprises a sensor unit (11), and a control unit (12). The sensor unit (11) is configured to detect a current C-arm distance between the C- arm (24) and the object. The control unit (12) is configured to control a movement of the C-arm (24) and to determine an adjustment to adjust the distance between the C-arm (24) and the object.

Description

DEVICE FOR CONTROLLING A MOVEMENT OF AN OBJECT AND A C-ARM OF AN IMAGING SYSTEM

FIELD OF THE INVENTION

The invention relates to a device for controlling a movement of an object and a C-arm of an imaging system relative to each other, an imaging system comprising such device, a method for controlling a movement of an object and a C-arm of an imaging system relative to each other, a computer program element for controlling such device or system for performing such method and a computer readable medium having stored such computer program element.

BACKGROUND OF THE INVENTION

For example, in complex adult and pediatric structural heart disease

interventions in a cath lab, C-arm computed tomography (C-arm CT) is an imaging modality that is increasingly used to generate 3D roadmaps of patient anatomy to assist in the guidance of these procedures. A medical three-dimensional X-ray imaging device comprising a C- shaped arm that can revolve around an axis of rotation through an object to be imaged is e.g. disclosed in WO 2006/070328 (Al). Therein, an X-ray source is attached to one end of the C- shaped arm, and an X-ray detector for receiving X-rays is attached to the other end of the C- shaped arm.

A C-arm CT scan involves a rotation of the X-ray C-arm around a patient to generate X-ray projections needed to produce a 3D reconstruction of the anatomy of the patient. This rotation is usually in excess of 160° to generate a sufficient number of image projections for the reconstruction. Right before a C-arm CT scan is performed in the cath lab, the patient is lying on the operating table and the physician must confirm that the C-arm can rotate through the full angulation around the patient before performing the scan.

At the present time, the confirmation that the C-arm is able to rotate fully around the patient before performing a C-arm CT scan must be verified manually by the physician. The C-arm is rotated to both its starting and ending scan angles before performing the desired C-arm CT scan. This is currently a rather cumbersome process due to the variation in size of patients on the table and the equipment connected to the patient and requires many patient and/or table adjustments to be carried out by the physician to ensure the C-arm is able to get around the patient for the full C-arm CT scan. This is further exacerbated by the fact that these multiple manual adjustments need to be done near both the starting and ending angles for the C-arm CT scan. These required manual patient or table positioning adjustments are rather disruptive to clinical workflow in the cath lab. These manual adjustments could also accidentally lead to collisions, with the potential to damage equipment or injure the patient.

SUMMARY OF THE INVENTION

Hence, there may be a need to provide a device for controlling a movement of an object and a C-arm of an imaging system relative to each other, which allows in an easy manner to avoid collisions between the C-arm and the environment.

The problem of the present invention is solved by the subject-matters of the independent claims, wherein further embodiments are incorporated in the dependent claims. It should be noted that the aspects of the invention described in the following apply also to the device for controlling a movement of an object and a C-arm of an imaging system relative to each other, the imaging system comprising such device, the method for controlling a movement of an object and a C-arm of an imaging system relative to each other, the computer program element, and the computer readable medium.

According to the present invention, a device for controlling a movement of an object and a C-arm of an imaging system relative to each other is presented. The device comprises a sensor unit and a control unit. The sensor unit is configured to detect a current C- arm distance between the C-arm and the object. The control unit is configured to control a movement of the C-arm on a movement path from a first position to a second position.

The first and second positions may be extremes, or in other words, start and end of an imaging or a preparational movement of the C-arm. The first position can be a start position of a preparational movement of the C-arm and a future end position of an upcoming imaging movement of the C-arm following the preparational movement. The second position can be an end position of a preparational movement of the C-arm and a future start position of an upcoming imaging movement of the C-arm following the preparational movement.

The control unit is further configured to compare the C-arm distance with a predefined minimum distance threshold between the C-arm and the object. In case the detected C-arm distance is smaller than the minimum distance threshold, the control unit is configured to determine an adjustment to adjust the distance between the C-arm and the object so that the C-arm distance is larger than the minimum distance threshold to achieve an adjusted movement path. The determination of the adjustment is based on the current C-arm distance and the second position to resume the movement of the C-arm to the second position. The movement may therefore end at the second or end position without any collision.

The determination of the adjustment is made depending on not only the current

C-arm distance just to increase the C-arm distance, but also depending on the second position to be achieved, so that the adjustment can be made in the correct direction to resume the movement of the C-arm to the second or end position.

As a result, a device for controlling a movement of an object and a C-arm of an imaging system relative to each other is provided, which allows avoiding collisions between the C-arm and the environment with potential damages to equipment or injuries to a patient in an easy manner.

The device for controlling a movement of an object and a C-arm can be used for an imaging movement of the C-arm as well as for a preparational movement for preparing the imaging movement of the imaging system. For example, before performing a desired C- arm CT scan, the C-arm can be rotated to both its starting and ending scan angles to confirm that the C-arm is able to rotate collision free around the patient, the table and the equipment. No manual adjustments need to be done, the clinical workflow is not disturbed, the physicians and the support staff can concentrate on other things and, thereby, the use of C-arm CT in the future is secured.

In other words, when e.g. an X-ray source or an X-ray detector of the C-arm is getting too close to the patient or a piece of equipment during the C-arm angle preparation stage right before the imaging scan, the device according to the invention adjusts the operating table and/or the C-arm position in an optimal way to ensure that the C-arm will be able to get around the patient all the way from the starting to the ending C-arm angle for the scan. This prevents the C-arm rotational motion from being interrupted and blocked as the scan is prepared and prevents the physician from having to manually make multiple positioning adjustments during C-arm scan preparation. Thereby, the workflow in a cath lab is simplified and improved. As a result, the workflow with and the usability of interventional X-ray C-arm systems is improved. The device according to the invention can be used with cardiac or non- cardiac clinical applications and C-arm systems.

The object may be a patient, a surface of a patient table, a surface of an equipment part and/or the like. In detail, the object may be at least one of the group of a patient, a surface of a patient table, a normal to the surface of the patient table, a surface of an equipment part or a normal to the surface of the equipment part.

The movement path may be provided to the control unit.

The C-arm distance may be the distance between the object and an X-ray source and/or an X-ray detector of the C-arm. The C-arm distance may be measured one, two or three dimensional.

The adjustment may be an adjustment motion configured to move the object and/or the C-arm to avoid a collision between the C-arm and the object. The adjustment motion may be configured to move the object with a horizontal and/or a vertical component and/or the object with a horizontal and/or a vertical component. Exemplarily, the

determination of the adjustment can be based on a previous adjustment.

As stated above, the device according to the invention can be used for an imaging movement of the C-arm as well as for a preparational movement for preparing the imaging movement of the imaging system. In the latter case, the movement of the C-arm is a preparational movement for preparing an imaging movement of the imaging system and the first and second positions are end positions of the C-arm during the imaging movement.

In an example, the control unit is then configured to control a movement of the C-arm from an arbitrary position to the first position. The arbitrary position may lie somewhere and in particular between the first and second positions. In the latter case, the movement of the C-arm from the first to the second position may be in a first direction and the movement of the C-arm from the arbitrary position to the first position may be in a second direction opposite to the first direction. In case the C-arm distance is smaller than the distance threshold, the control unit may be configured to determine an additional adjustment to adjust the distance between the C-arm and the object so that the C-arm distance is larger than the distance threshold. The determination of the additional adjustment may be based on the C-arm distance and the first position to resume the movement of the C-arm to the first position. The determination of the additional adjustment may also be based on the C-arm distance, the first position and the second position to resume the movement of the C-arm to the first and the second position.

Exemplarily, feedback about the adjustment is graphically and/or textually displayed on a monitor. The feedback may comprise e.g. information about an initial phase of the setup and (potential) adjustments. In addition, when the system is finally tuned for the rotation, appropriate feedback will be shown, so that the user will be always informed about the status of the system. In an example, the device for controlling a movement of an object and a C-arm of an imaging system relative to each other further comprises a warning unit configured to prompt the adjustment(s) in advance. Exemplarily, which specific part of the system will be adjusted (i.e. table or C-arm) can be prompted and/or in which direction the adjustment will take place. In such a way the staff present in the room can anticipate the movements of the system and act accordingly, if required.

Exemplarily, visual feedback can also be displayed in the form of coloured light emanating from the C-arm with e.g. shades changing and/or text updating the situation signifying whether the system is still adjusting to the proper position and/or is ready for further rotation. Exemplarily, the warning system can also recommend and display a possible alternative C-arm CT scan and/or display that a particular scan of a specific patient is not feasible.

In an example, the detected C-arm distance is a real time C-arm distance, wherein the control unit is configured to compare the C-arm distance repetitively with the predefined threshold distance, and wherein the control unit is configured to determine the adjustment(s) automatically.

In an example, the adjusted movement path is smoothened. The adjusted movement path may comprise abrupt changes in direction as soon e.g. an obstacle is detected. These abrupt changes can be smoothened, which means the smoothened adjusted movement path comprises softer changes in direction as they can e.g. be started earlier. Further, meanders can be omitted, whereby meanders can be evasive movements which turn out to be unsuccessful and therefore have to be retracted.

In an example, the device for controlling a movement of an object and a C-arm of an imaging system relative to each other further comprises a marker sensitive to radiation emitted by the sensor unit and configured to be arranged at the object to provide spatial feedback from the marker to the sensor unit. In other words, it may be possible to simplify and enhance detection and improve sensitivity for proximity sensors of the sensor unit by placing markers sensitive to radiation (ie. optical, infrared, electromagnetic) emitted by sensors on the patient, patient table, or on the equipment. In the case of table collisions, these markers could be pre-installed on the table.

In an example, the control unit is further configured to compare the C-arm distance with a predefined collision avoiding distance between the C-arm and the object, wherein the collision warning distance is smaller than the above mentioned minimum distance threshold. In case the C-arm distance is smaller than the collision warning distance data, the control unit may be configured to stop any motion of the object and/or the C-arm. In other words, the control unit can also comprise an interlock to stop C-arm and table motion if the sensor unit signal gets below a specified value below the threshold signal or immediately upon contact with a surface. The option to revert to manual C-arm and table adjustment can always remain available.

According to the present invention, also an imaging system is presented. The imaging system comprises a C-arm and the device as described above. The device is configured to control a movement of the C-arm. The C-arm can be placed either at a head of an operating table, in which case the C-arm CT scan will cause the C-arm to rotate around the patient in a "propeller" acquisition, or the C-arm can be placed at a side of the table, in which case the C-arm CT scan will cause the C-arm to rotate in a "roll" acquisition around the patient.

According to the present invention, also a method for controlling a movement of an object and a C-arm of an imaging system relative to each other is presented. The method comprises the following steps, not necessarily in this order:

a) controlling a movement of the C-arm on a movement path from a first position to a second position,

b) detecting a current C-arm distance between the C-arm and the object, c) comparing the C-arm distance with a predefined minimum distance

threshold between the C-arm and the object, and, d) in case the C-arm distance is smaller than the minimum distance

threshold, determining an adjustment to adjust the distance between the C-arm and the object so that the C-arm distance is larger than the minimum distance threshold data to achieve an adjusted movement path.

The determination of the adjustment is based on the C-arm distance and the second position to resume the movement of the C-arm to the second position.

In an example, the method controls a movement of the C-arm from an arbitrary position to the first position. The arbitrary position may lie between the first and second position. Then, the movement of the C-arm from the first to the second position may be in a first direction and the movement of the C-arm from the arbitrary position to the first position may be in a second direction opposite to the first direction. In case the C-arm distance is smaller than the distance threshold, an additional adjustment may be determined to adjust the distance between the C-arm and the object so that the C-arm distance is larger than the distance threshold. The determination of the additional adjustment may be based on the C-arm distance, the first position and the second position to resume the movement of the C-arm to the first and the second position.

According to the present invention, also a computer program element is presented, wherein the computer program element comprises program code means for causing the imaging system as defined in the independent claim to carry out the steps of the method as defined in the independent claim when the computer program is run on a computer controlling the imaging system.

It shall be understood that the device, the imaging system, the method, the computer program element for controlling such device and the computer readable medium having stored such computer program element according to the independent claims have similar and/or identical preferred embodiments, in particular, as defined in the dependent claims. It shall be understood further that a preferred embodiment of the invention can also be any combination of the dependent claims with the respective independent claim.

These and other aspects of the present invention will become apparent from and be elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will be described in the following with reference to the accompanying drawings:

Fig. 1 shows a schematic drawing of an example of an imaging system for controlling a movement of an object to be examined and a C-arm relative to each other.

Fig. 2 shows schematically and exemplarily an embodiment of a movement of the C-arm.

Fig. 3 shows basic steps of an example of a method for controlling a movement of an object and a C-arm of an imaging system relative to each other.

Fig. 4 shows a schematic overview of steps of a method for controlling a movement of an object and a C-arm of an imaging system relative to each other in more detail.

DETAILED DESCRIPTION OF EMBODIMENTS

Fig. 1 shows schematically and exemplarily an embodiment of an imaging system 1 according to the invention for controlling a movement of an object to be examined (not shown) and a C-arm 24 relative to each other. The imaging system 1 comprises the C- arm 24 and a device 10 for controlling a movement of the object and the C-arm 24 relative to each other.

The C-arm 24 is provided such that a movement of the C-arm 24 around an object is possible to be able to adapt the viewing direction. An X-ray source 18 and an X-ray detector 20 are at least partially mounted on the C-arm 24 such that a table 22 can be arranged between the X-ray source 18 and the X-ray detector 20, and that the object can be placed between the X-ray source 18 and the X-ray detector 20.

The imaging system 1 may further comprise a display 28 arranged in the vicinity of the table 22 to provide information to the user, for example a surgeon. Also an interface unit 30 can be arranged to provide the possibility to further control the imaging system 1.

In use, the object, for example a patient, can be located on the table 22 between the X-ray source 18 and the X-ray detector 20 during a radiation procedure. The X-ray detector 20 may provide detected raw image data to a processing unit 14.

The device 10 for controlling a movement of the object and the C-arm 24 relative to each other comprises a sensor unit 11 and a control unit 12. The sensor unit 11 detects a current C-arm distance between the C-arm 24 and the object. The control unit 12 controls a movement of the C-arm 24 on a movement path from a first position to a second position and compares the C-arm distance with a predefined minimum distance threshold between the C-arm 24 and the object. In case the detected C-arm distance is smaller than the minimum distance threshold, the control unit 12 determines an adjustment to adjust the distance between the C-arm 24 and the object so that the C-arm distance is larger than the minimum distance threshold to achieve an adjusted movement path. The determination of the adjustment is based on the C-arm distance and the second position to resume the movement of the C-arm 24 to the second position.

Fig. 2 shows schematically and exemplarily an embodiment of a movement of the C-arm 24. The control unit 12 controls the movement of the C-arm 24 from an arbitrary position A to a first position B. The arbitrary position A lies between the first position A and a second position C. The movement of the C-arm 24 from the first position B to the second position C is in a first direction and the movement of the C-arm 24 from the arbitrary position A to the first position B is in a second direction opposite to the first direction. In case the C- arm distance is smaller than the distance threshold, the control unit 12 determines an additional adjustment to adjust the distance between the C-arm 24 and the object so that the C-arm distance is larger than the distance threshold. The determination of the additional adjustment is based on the C-arm distance, the first position B and the second position C to resume the movement of the C-arm 24 to the first and the second position.

Fig. 3 shows a schematic overview of steps of a method for controlling a movement of an object and a C-arm 24 of an imaging system 1 relative to each other. The method comprises the following steps, not necessarily in this order:

In a first step S 1 , controlling a movement of the C-arm 24 on a movement path from a first position to a second position.

- In a second step S2, detecting a current C-arm distance between the C- arm 24 and the object.

In a third step S3, comparing the C-arm distance with a predefined minimum distance threshold between the C-arm 24 and the object.

In a fourth step S4, in case the C-arm distance is smaller than the minimum distance threshold, determining an adjustment to adjust the distance between the C- arm 24 and the object so that the C-arm distance is larger than the minimum distance threshold data to achieve an adjusted movement path.

The determination of the adjustment is based on the C-arm distance and the second position to resume the movement of the C-arm 24 to the second position.

Fig. 4 shows a schematic overview of steps of a method for controlling a movement of an object and a C-arm 24 of an imaging system 1 relative to each other in more detail. For example, a button on a tableside will initiate a movement of the C-arm 24 towards an end rotation angle of a C-arm imaging scan. As the C-arm 24 rotates, the sensor unit 11 in either the X-ray source 18 or X-ray detector 20 (or both) will send out a signal to a control unit 12 to detect in real-time the position of the X-ray source 18 or X-ray detector 20 relative to a surface that they are close to colliding with.

Fig. 4 shows a solution for automatically adjusting patient position for the C- arm scan during its preparation. As the X-ray source 18 (or X-ray detector 20) gets close to a surface, instead of initiating an interlock preventing further C-arm movement at this point, the current C-arm distance between the C-arm 24 and the object (given by a sensor signal S) will be compared with a preset minimum distance threshold (given by threshold signal T) to determine if action must be taken to move the patient. If the C-arm distance or X-ray source 18 (or X-ray detector 20) to surface distance signal S is less than or equal to this threshold distance signal T, then the control unit 12 (such as a comparator) will send an output signal to the interventional X-ray system to automatically adjust the patient table position such that the X-ray source 18 or X-ray detector 20 will be able to get around the patient without collision during C-arm scan preparation.

The sensors in both the X-ray source 18 and detector can each have their own comparator such that the distances of either to the patient surface could be monitored simultaneously. The relative amount of required height and lateral adjustment for the table 22 could be determined by using the current C-arm angle relative to the patient table surface or line perpendicular to the table surface (the normal). Since the X-ray source 18 (or X-ray detector 20) to surface distance signal S is monitored in real time, the C-arm 24 will be able to resume rotation again once the minimum distance threshold signal T is exceeded by the sensor signal S, the current C-arm distance between the C-arm 24 and the object. This feedback algorithm will continue until the final rotation angle for the C-arm scan is reached. The table position and C-arm lateral position would then be recorded in the system.

If patient table adjustment proves to be problematic, the algorithm will also attempt to perform a fine lateral adjustment of the C-arm position to facilitate rotation to the final angle. The algorithm would be able to alternate between fine table and C-arm lateral position adjustment as needed to reach the final scan angle. Once this final angle is reached, the C-arm 24 would automatically start rotating towards the starting scan angle and this algorithm would be repeated until the C-arm 24 is at the starting angle position for the scan.

If the table 22 or C-arm position adjustment for C-arm scan starting angle causes problems for the final scan angle to be reached, then the algorithm will attempt to optimize patient table 22 and C-arm lateral position for both the starting and ending angles for the scan simultaneously.

As an additional embodiment, a color-coded warning system with text updating the situation (ie. green if signal is safely beyond distance threshold, yellow if approaching threshold, red if sensor signal is less than the threshold signal) could be implemented into the algorithm and displayed to the physician on the large display in the cath lab while the C-arm scan preparation is taking place.

This embodiment can also include an interlock to stop C-arm 24 and table motion if the sensor signal somehow gets below a specified value below the threshold signal or immediately upon contact with a surface. The option to revert to manual C-arm and table adjustment would always remain available. Although a very rare occurrence, the warning system can also display that a particular scan of a specific patient is not feasible if all of these redundancies and automatic adjustments fail.

As a further embodiment, the warning system can also recommend and display a possible alternative C-arm CT scan that could be attempted at reduced angulation or from a different position based on the parameters of the previously attempted C-arm scan.

As an additional embodiment, it may be possible to simplify and enhance detection and improve sensitivity for the proximity sensors by placing markers sensitive to the radiation (ie. optical, infrared and electromagnetic) emitted by sensors on the patient, patient table 22, or on the equipment connected to the patient. In the case of table collisions, these markers could be pre-installed on the table 22.

Although most standard C-arm CT scans are done using oblique C-arm angulation exclusively, an additional embodiment extends this algorithm to account for a scan that uses a cranial/caudal C-arm angulation component as well. In this case, it may be helpful to expand the algorithm to facilitate adjustment of the longitudinal position (head- feet direction) of the table 22 and/or C-arm 24 as well during C-arm CT scan preparation.

In another exemplary embodiment of the present invention, a computer program or a computer program element is provided that is characterized by being adapted to execute the method steps of the method according to one of the preceding embodiments, on an appropriate system.

The computer program element might therefore be stored on a computer unit, which might also be part of an embodiment of the present invention. This computing unit may be adapted to perform or induce a performing of the steps of the method described above. Moreover, it may be adapted to operate the components of the above described apparatus. The computing unit can be adapted to operate automatically and/or to execute the orders of a user. A computer program may be loaded into a working memory of a data processor. The data processor may thus be equipped to carry out the method of the invention.

This exemplary embodiment of the invention covers both, a computer program that right from the beginning uses the invention and a computer program that by means of an up-date turns an existing program into a program that uses the invention.

Further on, the computer program element might be able to provide all necessary steps to fulfil the procedure of an exemplary embodiment of the method as described above. According to a further exemplary embodiment of the present invention, a computer readable medium, such as a CD-ROM, is presented wherein the computer readable medium has a computer program element stored on it, which computer program element is described by the preceding section.

A computer program may be stored and/or distributed on a suitable medium, such as an optical storage medium or a solid state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems.

However, the computer program may also be presented over a network like the World Wide Web and can be downloaded into the working memory of a data processor from such a network. According to a further exemplary embodiment of the present invention, a medium for making a computer program element available for downloading is provided, which computer program element is arranged to perform a method according to one of the previously described embodiments of the invention.

It has to be noted that embodiments of the invention are described with reference to different subject matters. In particular, some embodiments are described with reference to method type claims whereas other embodiments are described with reference to the device type claims. However, a person skilled in the art will gather from the above and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters is considered to be disclosed with this application.

However, all features can be combined providing synergetic effects that are more than the simple summation of the features.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing a claimed invention, from a study of the drawings, the disclosure, and the dependent claims.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfil the functions of several items re-cited in the claims. The mere fact that certain measures are re-cited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A device (10) for controlling a movement of an object and a C-arm (24) of an imaging system (1) relative to each other, comprising:

a sensor unit (11), and

a control unit (12),

wherein the sensor unit (11) is configured to detect a current C-arm distance between the C-arm (24) and the object,

wherein the control unit (12) is configured to control a movement of the C-arm

(24) on a movement path from a first position to a second position,

wherein the control unit (12) is configured to compare the C-arm distance with a predefined minimum distance threshold between the C-arm (24) and the object, and, in case the detected C-arm distance is smaller than the minimum distance threshold, the control unit (12) is further configured to detemiine an adjustment to adjust the distance between the C-arm (24) and the object so that the C-arm distance is larger than the minimum distance threshold to achieve an adjusted movement path, and

wherein the determination of the adjustment is based on the C-arm distance and the second position to resume the movement of the C-arm (24) to the second position.

2. Device (10) according to claim 1, wherein the movement of the C-arm (24) is a preparational movement for preparing an imaging movement of the imaging system (1) and wherein the first and second positions are end positions of the C-arm (24) during the imaging movement.

3. Device (10) according to claim 1 or 2, wherein the control unit (12) is configured to control a movement of the C-arm (24) from an arbitrary position to the first position, wherein in case the C-arm distance is smaller than the distance threshold, the control unit (12) is configured to detemiine an additional adjustment to adjust the distance between the C-arm (24) and the object so that the C-arm distance is larger than the distance threshold, and wherein the determination of the additional adjustment is based on the C-arm distance, the first and the second position to resume the movement of the C-arm (24) to the first and the second position.

4. Device (10) according to the preceding claim, wherein the arbitrary position is between the first and second positions and wherein the movement of the C-arm (24) from the first to the second position is in a first direction and the movement of the C-arm (24) from the arbitrary position to the first position is in a second direction opposite to the first direction.

5. Device (10) according to one of the preceding claims, further comprising a warning unit configured to prompt the adjustment(s) in advance.

6. Device (10) according to one of the preceding claims, wherein the detected C- arm distance is a real time C-arm distance, wherein the control unit (12) is configured to compare the C-arm distance repetitively with the predefined threshold distance, and wherein the control unit (12) is configured to determine the adjustment(s) automatically.

7. Device (10) according to one of the preceding claims, wherein the adjusted movement path is smoothened.

8. Device (10) according to one of the preceding claims, further comprising a marker sensitive to radiation emitted by the sensor unit (11) and configured to be arranged at the object to provide spatial feedback from the marker to the sensor unit (11).

9. Device (10) according to one of the preceding claims, wherein the control unit (12) is further configured to compare the C-arm distance with a predefined collision avoiding distance between the C-arm (24) and the object, wherein the collision warning distance is smaller than the minimum distance threshold, and,

in case the C-arm distance are smaller than the collision warning distance data, the control unit (12) is configured to stop any motion of the object and/or the C-arm (24).

10. An imaging system ( 1 ) , comprising

a C-arm (24), and

a device (10) according to one of the preceding claims, wherein the device (10) is configured to control a movement of the C-arm (24).

11. A method for controlling a movement of an object and a C-arm (24) of an imaging system (1) relative to each other, comprising the following steps:

a) controlling a movement of the C-arm (24) on a movement path from a first position to a second position,

b) detecting a current C-arm distance between the C-arm (24) and the object, c) comparing the C-arm distance with a predefined minimum distance threshold between the C-arm (24) and the object, and,

d) in case the C-arm distance is smaller than the minimum distance threshold, determining an adjustment to adjust the distance between the C-arm (24) and the object so that the C-arm distance is larger than the minimum distance threshold data to achieve an adjusted movement path, wherein the determination of the adjustment is based on the C-arm distance and the second position to resume the movement of the C-arm (24) to the second position.

12. Method according to the preceding claim, further comprising controlling a movement of the C-arm (24) from an arbitrary position to the first position, and in case the C- arm distance is smaller than the distance threshold, determining an additional adjustment to adjust the distance between the C-arm (24) and the object so that the C-arm distance is larger than the distance threshold, wherein the determination of the additional adjustment is based on the C-arm distance, the first and the second position to resume the movement of the C-arm (24) to the first and the second position.

13. Method according to one of the preceding claims, further comprising a prompting of the adjustment in advance.

14. A computer program element for controlling a device (10) or system according to one of the claims 1 to 10, which, when being executed by a control unit (12), is adapted to perform the method steps of the preceding claims.

15. A computer readable medium having stored the computer program element of the preceding claim.