REVERSE HELICAL X-RAY TOMOGRAPHY WITH A CEILING MOUNTED C-ARM SYSTEM

FIELD OF INVENTION

The invention relates to an x-ray examination device as well as a method for three-dimensional imaging of an object of interest, a program element and an image processing device. Particularly, the invention relates to an x-ray examination device by means of which a reverse helical x-ray tomography with a ceiling mounted C-arm system can be performed.

BACKGROUND OF INVENTION

The generation of three-dimensional image information of objects of interest by means of systems which are commonly used during medical interventions, e.g. C-arm, is currently limited to movements of the tube-detector system on a spherical surface and along so called "multiple circular arcs" (cf. G. Lauritsch, J. Boese, L. Wigstrόm, H. Kemeth, and R. Fahrig: "Towards Cardiac C-arm Computed Tomography," IEEE Transactions on Medical Imaging, 2006, Vol. 25(7), pp. 922-934). Therefore, it is a limitation of these trajectories that no large coverage of an object along the patient axis can be achieved.

With a usual computer tomography (CT) system it is possible to acquire three- dimensional images of an object with a large coverage along the patient axis. But therefore, the patient has to be moved along his axis through the CT device. However, during a medical intervention, it is not appropriate to change the patient's position because the patient is connected to several tubes and cables that can disconnect easily when the patient's position is changed. Moreover the CT devices are very large-sized which significantly interferes the freedom of movement inside the intervention room.

In contrast to standard CT systems, the x-ray imaging system of a medical C- arm examination system which is typically used during interventions is mounted on an open C-arm device that has limited rotational capabilities in terms of speed and movement range.

Due to the mechanical construction, today's C-arm devices are merely capable to perform the so called "short scan" movement during projection acquisition which resembles slightly more than a half plane circle rotation (180 degrees plus fan angle of the x-ray beam, typically perpendicular to the patient table). Due to that mechanical limitation, the usual reconstruction approach of CT systems cannot be applied for acquiring fully spatially resolved three- dimensional images by using a C-arm system.

Moreover, due to the mechanical construction of a common C-arm system, a large coverage of an object along the patient axis cannot be achieved.

WO 98/24368 describes a conventional medical x-ray apparatus which may be formed as an assembly consisting of a stand, a support which supports an x-ray source at one end and an x-ray detector at its other end and a patient table. The support is formed by a circular C-arc. The C-arc is mounted on a carriage which is displaceable in the longitudinal direction of the patient table, to preposition the C-arc before a scanning procedure.

SUMMARY OF THE INVENTION

It may be an object of the invention to provide a C-arm based x-ray examination device which provides three-dimensional images of an object of interest during an intervention.

This may be achieved by the subject matter according to the independent claims. Further embodiments of the present invention are described in the respective dependent claims.

Generally, a x-ray examination device according to the invention may comprise a C-arm, the C-arm comprising a C-shaped element, a x-ray tube, a x-ray detector, wherein the x-ray tube and the x-ray detector are arranged in opposite position relative to each other on the C-shaped element, wherein the C-shaped element is capable of performing a roll movement, wherein the C-shaped element is capable of performing a movement in a sideward direction such that the x-ray tube and the x-ray detector may be movable along a helical path segment relative to e.g. a stationary patient.

In other words, the first embodiment of the present invention may be seen as based on the idea to provide a device which is adapted to acquire x-ray data of an object of interest from different positions by moving a x-ray tube and a x-ray detector of a medical C- arm system on a specific acquisition geometry or acquisition path around and along the object for achieving a large coverage along the patient's axis. This specific path may be

obtained by combining different movement directions of components of the x-ray device according to the invention.

The acquired raw data may be further processed to reconstruct three- dimensional images of the object of interest. The x-ray examination device according to the invention may be used in interventional applications.

The x-ray examination device according to the invention may be used for imaging of legs, e.g. for knee replacement surgery, where a three-dimensional reconstruction of a complete leg may be required for prosthesis replacement. The x-ray examination device may be further used in the trauma area, imaging of head and neck and three-dimensional bolus imaging in the extremities.

The x-ray examination device according to the invention may be used in hospital or medical practice.

In the following, possible details, features and advantages of the x-ray examination device according to the invention will be explained in detail.

The C-arm may be a conventional medical C-arm system.

The C-shaped element may be an element formed in a C-form. The C-shaped element may be a part of the C-arm.

The x-ray tube may be any kind of x-ray emitter, e.g. a vacuum bulb, which emits x-ray when electrons which are accelerated by a high voltage generator interact with a target in the x-ray tube. The x-rays may be emitted in cone beam form or any other suitable emitting manner.

The x-ray detector may be any kind of analogous or digital x-ray detector (e.g. CCD-detector), receiver or image intensifier, which may comprise various x-ray sensors, e.g. an array of single x-ray sensors or rows of x-ray sensors.

The x-ray tube and the x-ray detector are arranged in opposite position relative to each other on the C-shaped element, i.e. the x-ray tube and the x-ray detector may be arranged on the two ends of the C of the C-shaped element such that the x-ray beam which is emitted by the x-ray tube may be received by the x-ray detector. With an x-ray examination device according to the invention, an area may be examined, in which preferably an object of interest may be positioned. This area may comprise an isocentre. The C-shaped element may be adapted to move around the isocentre. Various axes may pass through the isocentre. The C-shaped element may move around one of these axes, wherein the axis may preferably be in parallel to the longitudinal axis of a table

on which an object of interest is positioned. Such a movement direction of the C-shaped element may be defined as roll movement.

The isocentre may move along an axis, which may preferably be in parallel to the longitudinal axis of a table. Such a movement direction of the isocentre may be defined as movement in sideward direction.

In other words, the C-shaped element may define a plane in which the "C" is located. Therefore, the axis around which the C-shaped element is moving, stands substantially perpendicularly on said plane, i.e. the roll movement of the C-shaped element is performed in said plane, and the isocentre is also located substantially in said plane. A movement in sideward direction of the isocentre means, that the C-shaped element may move sidewards along a, for example, a table on which an object of interest might be positioned. Thus, the C-shaped element might be moving along a length of the object of interest, while the C-shaped element is rolling around said object.

By way of a combination of roll movement and movement in sideward direction, the x-ray tube and the x-ray detector are movable along a helical path segment. This means, that the position of the x-ray tube and the x-ray detector may change along a course of a three-dimensional, twisted shape when the x-ray tube and the x-ray detector are moved by the roll movement and movement in sideward direction.

The x-ray projection frame rate may be a function of the roll movement velocity of the C-shaped element, e.g. linear.

According to another embodiment of the present invention, the x-ray examination device may further comprise a controlling unit, wherein the controlling unit is adapted to control the C-arm such that the C-shaped element is performing the roll movement and the movement in sideward direction simultaneously. The controlling unit may be separated from the C-arm or comprised e.g. in the

C-arm. The controlling unit may be coupled via cables, electrical conductors or wireless connection with all devices which are connected and communicate with the controlling unit and vice versa. The "controlling unit" may send control commands to different motors of the x-ray examination device, preferably to the motors for effecting the roll movement and the movement in sideward direction. The controlling unit may be adapted to send the control commands separately or simultaneously and to send signals to reverse the movement direction of each of the movement motors. The controlling unit may be adapted to send control commands to the x-ray tube and the x-ray detector. The controlling unit may process data acquired by position sensors as described below.

According to another embodiment of the present invention, the roll movement and/or the movement in sideward direction of the x-ray examination device may be changeable.

The movement direction of the roll movement may be reversed and/or the movement velocity may be changed, i.e. decelerate, stop or accelerate, separately or simultaneously. The movement direction of the movement in sideward direction may be changed and/or the movement velocity may be changed, i.e. decelerate, stop or accelerate, separately or simultaneously. Both the different changes of roll movement and the mentioned changes of movement in sideward direction may occur separately or simultaneously. Both movements may not be of constant velocity, since the C-shaped element may need deceleration and acceleration in turning points of the roll movement. The velocity of the sideward movement may be a function of the roll movement velocity, e.g. linear.

According to another embodiment of the present invention, the x-ray tube and the x-ray detector of the x-ray examination device may be movable along an alternating helical path.

As mentioned above, the position of the x-ray tube and the x-ray detector may change along a course of a three-dimensional, twisted shape when the x-ray tube and the x- ray detector are moved by the roll movement and the movement in sideward direction. This may be achieved by performing a roll movement of the C-shaped element while moving the C-arm in a sideward direction simultaneously. Due to technical characteristics it may be not possible to effect a roll movement of the C-shaped element over a range of 360° with the same rotation direction. However, it may be possible to reverse the rotation direction and to perform a further roll movement in opposite direction.

According to this, alternating helical path movement may signify a combination of roll movement and movement in sideward direction, wherein the rotation direction of the roll movement may change.

According to another embodiment of the present invention, the examination device may further comprise a position sensor for detecting a position of the x-ray tube and the x-ray detector. The positions of the different elements of the x-ray examination device in relation to each other and/or in relation to any coordinate systems may be detected by position sensors. The data acquired by the position sensors may be used for further data processing, e.g. in the controlling unit. By way of the position data, the position of the x-ray

tube and x-ray detector might be calibrated and it might be possible to assign position data to data of the x-ray detector.

According to another embodiment of the present invention, the examination device may further comprise an imaging device. The imaging device may process data obtained by the x-ray detector and any other suitable data to reconstruct three-dimensional images of the object of interest. The imaging device may comprise a display unit. The imaging device may be separated from the C-arm or at least partially comprised in the C-arm. The display unit may be a monitor which is separated from the C-arm. The imaging device and/or the display unit may be coupled via cables, electrical conductors or wireless connection with all devices which are connected and communicate with the imaging device and/or the display unit and vice versa.

According to another embodiment of the present invention, the examination device may further comprise a processing unit for controlling both the C-arm movements and an imaging device, for reconstructing three-dimensional images of an object of interest. For acquiring three-dimensional images of an object of interest by data reconstruction it may be necessary to adapt the C-arm movements, the x-ray tube and the x- ray detector as well as the processes of the imaging device to each other. This may be effected by a processing unit. The processing unit may comprise the controlling unit and the imaging device. The processing unit may be separated from the C-arm or at least partially comprised e.g. in the C-arm. The processing unit may be an external computer. The processing unit may be coupled via cables, electrical conductors or wireless connection with all devices which are connected and communicate with the processing unit and vice versa.

According to another embodiment of the present invention, the imaging device of the x-ray examination device may be adapted to perform a data reconstruction by means of a filtered back projection or an iterative reconstruction scheme.

The data reconstruction may be performed according to algorithms as described in S. Cho, D. Xia, and X. Pan: "Exact Image Reconstruction in Reverse Helical Cone-Beam CT"; Proc. Fully 3D Meeting, Lindau, Germany, 2007, pp. 84-87.

According to another embodiment of the present invention, a method for three- dimensional imaging of an object of interest by means of an x-ray examination device may comprise the steps: moving the x-ray tube and the x-ray detector along a helical path; radiographing the object of interest from different positions; acquiring raw data by the x-ray detector; reconstructing images of the object of interest based on the raw data by an imaging device; and displaying the images on a display device.

The steps may be performed several times. The single steps may be performed in dependence from each other. The object of interest may be e.g. any living or dead human or animal body, antiquities, mummies, structural elements and devices, etc.

According to another embodiment of the present invention, the imaging device of the x-ray examination apparatus may be adapted for three-dimensional imaging of objects having a length in the direction of the movement in sideward direction of the C-shaped element.

Approximate three dimensional images around the plane of the C-shaped element may be obtained by a reconstruction of data merely acquired with small cone angles by a roll movement of the C-shaped element around an object. For obtaining exact three- dimensional images of the object also at high cone angles, it may be necessary to acquire additional information from projection angles outside this single plane. This may be information disseminated along a longitudinal axis of the object.

When a human body is located on a table, the longitudinal axis of the human body usually is in parallel to the longitudinal axis of the table. Due to technical reasons, the movement in sideward direction of the plane in which the C-shaped element is located may usually take place perpendicular to the longitudinal axis of such a table. Therefore, it may be necessary that an object having a certain length may be orientated with its longitudinal axis perpendicular to the plane in which the C-shaped element is located. According to another embodiment of the present invention, the steps of moving the x-ray tube and the x-ray detector along a helical path, of radiographing the object of interest from different positions, and of acquiring raw data by the x-ray detector may be performed simultaneously.

During the simultaneous roll movement and movement in sideward direction of the C-shaped element along a helical path as described above, the x-ray tube may emit x- ray in direction to the object of interest which may be received and output as raw data by the x-ray detector. This means that the movements of the C-shaped element and radiographing the object of interest may be a continuous process.

According to another embodiment of the present invention, the method may further comprise a step of defining a neutral position of the C-arm by performing a calibration measurement.

It may be necessary to perform a calibration measurement for detecting the effectively performed movement of the x-ray tube and the x-ray detector in relation to the object of interest, which presupposes the repeatability of the movement. For the calibration

measurement there may be used a phantom, in which small high-absorbing globules may be disseminated. The globules' three-dimensional position may be known sufficiently a priori.

The globules may cover the whole field-of-view of the reverse helical trajectory.

According to another embodiment of the present invention, there is provided a method for three-dimensional imaging of an object of interest, wherein the step of reconstructing images includes a data reconstruction by means of an iterative reconstruction scheme or a filtered back projection, wherein the proposed reconstruction algorithm by Cho,

Xia and Pan is exact in the mathematical sense and can be called also a "reconstruction scheme". According to another embodiment of the present invention, there is provided a method for three-dimensional imaging of an object of interest, wherein the step of reconstructing images utilizes information of a position sensor.

For reconstructing the images it may be necessary to correlate the raw data, which are acquired at a specific position by the x-ray detector, with the corresponding specific position of the x-ray tube and the x-ray detector in relation to the object of interest.

Position information may be obtained from the position sensors.

According to another embodiment of the present invention, a computer readable medium is provided, in which a computer program is stored for performing the method according to the invention. According to another embodiment of the present invention, a program element is provided wherein the program element, when being executed, controls the X-ray examination device for generating three-dimensional images of an object of interest.

According to another embodiment of the present invention, there is provided an image processing device in which a computer program is executed, wherein the processing device is adapted to control the movements of an x-ray examination device, and to control an imaging device so that the imaging device is reconstructing three-dimensional images of an object of interest.

The invention relates also to a computer program for an image processing device, such that the method according to the invention might be executed on an appropriate system. The computer program is preferably loaded into a working memory of a data processor. The data processor is thus equipped to carry out the method of the invention. The computer program may be stored at a computer readable medium, such as a CD-Rom. The computer program may also be presented over a network like the worldwide web and can be downloaded into the working memory of a data processor from such a network.

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 apparatus type claims. However, a person skilled in the art will gather from the above and the following description that, unless other 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.

The aspects defined above and further aspects, features and advantages of the present invention can also be derived from the examples of embodiments to be described hereinafter and are explained with reference to examples of embodiments. The invention will be described in more detail hereinafter with reference to examples of embodiments but to which the invention is not limited.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a schematic representation of an x-ray examination device according to the invention. Fig. 2 shows a schematic representation of a processing unit according to the invention.

Fig. 3 shows a schematic representation of e.g. the x-ray source of the C-arm moving along an alternating helical path.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As illustrated in Fig. 1 , an x-ray examination device according to the invention comprises a C-shaped element 2. The C-shaped element 2 is connected via a first connecting joint (not shown) with a first holder element 30 which partially encompasses and embeds the C-shaped element 2 so that the C-shaped element 2 can be moved along its own C-shape. Therefore, the C- shaped element 2 can be positioned so that a roll movement 6 around an object of interest 32 is possible. In other words, the C-shaped element 2 can be moved so that the rotation axis of the C-shaped element 2 stands perpendicular to the plane in which the C-shaped element is located. Preferably, the C-shaped element 2 can be rolled around a horizontal axis, which is in parallel to the longitudinal axis of a table 10.

Preferably, before performing an examination by means of the x-ray examination device according to the invention, the C-shaped element 2 is positioned so that the "C" of the C-shaped element is in vertical position.

The roll movement 6 may cover an angle of up to 180° in one direction, preferably 180° plus fan angle. The roll movement in the first connecting joint may be achieved by means of a motor (not shown).

The C-shaped element 2 is connected via a second connecting joint 34 with a L-shaped element 36. The C-shaped element 2 can be moved around an axis which is in parallel to a plane in which the C-shaped element 2 is located. The rotation axis of the second connecting joint 34 passes substantially through the isocentre. The C-shaped element 2 can be moved around said axis so that a propeller movement of the C-shaped element 2 can be performed.

Preferably, before performing an examination by means of the x-ray examination device according to the invention, the C-shaped element 2 may be moved to a position in which the plane of the C-shaped element 2 is in parallel to the plane of the L- shaped element 36.

The movement in the second connecting joint 34 may be achieved by means of a motor (not shown).

The L-shaped element 36 is connected via a third connecting joint 38 with a second holder element 40. The L-shaped element 36 can be moved around an axis which is substantially perpendicular to the rotation axis of the second connecting joint 34. The rotation axis of the third connecting joint 38 also passes substantially through the isocentre.

Preferably, before performing an examination by means of the x-ray examination device according to the invention, the L-shaped element 36 is moved to a position so that the plane of the C-shaped element 2 is located perpendicular to the longitudinal axis of a table 10.

The movement in the third connecting joint 38 may be achieved by means of a motor (not shown).

The second holder element 40 is connected via a forth connecting joint (not shown) with a guide rail 7. The guide rail may be mounted on the ceiling, on the floor, on a sidewall or on suitable device.

Preferably, the second holder element 40 can be moved in the guide rail 7 in parallel to the longitudinal axis of the table 10 so that the plane of the C-shaped element 2 performs a movement along the longitudinal axis of the table 10.

The movement in sideward direction 9 in the forth connecting joint may also be achieved by means of a motor (not shown).

For example, in case that the guide rail 7 is wall-mounted, the orientation of the axes of the second and third connecting joint 34, 38 may be interchanged. That means that the axis of the third connecting joint is horizontally orientated and the axis of the second connecting joint might preferably be vertically orientated.

Mainly, the degrees of freedom of movement of the C-shaped element 2 which comprises the x-ray tube 3 and the x-ray detector 4, are determined by the first, second and third connecting joint so that the x-ray tube 3 and the x-ray detector 4 can be moved on a spherical surface around the isocentre.

An additional degree of freedom of movement of the C-shaped element is determined by the forth connecting joint, so that the C-shaped element can be moved along the guide rail 7, i.e. in sideward direction.

The x-ray tube 3 and the x-ray detector 4 are arranged in opposite position relative to each other on the ends of the C-shaped element 2. The x-ray tube 3 may emit x-ray into an object of interest 32 which is located between the x-ray tube 3 and the x-ray detector 4.

The object of interest 32 can be positioned on the table 10. The table 10 may be arranged on a table carrier 11 or alternatively, on a sideward mounting (not illustrated), so that the room under the table may be free accessible. The table 10 may be movable in different directions, the movements may be effected by motor.

A display unit 12 can display the images reconstructed by the imaging device (not illustrated).

Fig. 2 shows a schematic representation of a processing unit 8 according to the invention. The processing unit 8 comprises the controlling unit 15 and the imaging device 17. The controlling unit or parts of the controlling unit may be comprised e.g. in the C-arm, in a desktop computer, in a control panel, etc.

The controlling unit sends commands to the movement motors 19 of the C- arm to control the roll movement and/or the movement in sideward direction. There may be also send commands to additional motors. Moreover, the controlling unit sends commands to the x-ray-tube 3 to control the emission of x-ray. The controlling unit may further send commands to the x-ray detector 4 to control the detection of x-ray.

The commands may comprise signals for starting, stopping, accelerating and decelerating the movement velocity, reversing the movement direction, etc. of the movement

motors and for switching on, switching of, increasing and decreasing the tube voltage and tube current, increasing and decreasing the pulse rate of the x-ray tube 3, etc.

The controlling unit coordinates the movements of the C-arm and the x-ray emission of the x-ray tube 3. The controlling unit may further coordinate the x-ray examination device of the invention as well as movements or the positioning of the table.

The imaging device 17 is adapted to reconstruct images based on the raw data acquired by the x-ray detector 4. The reconstruction of images may be effected by an algorithm based on filtered back projection or an iterative reconstruction scheme or any other appropriate reconstruction method. After reconstruction, the images are displayed on a display unit 12 or used for further processes.

The processing unit 8 is also adapted to use further external input signals, e.g. signals of position sensors 23, user commands 25 or any other information 27, e.g. data information of pre-existing images, data of a navigation system, etc.

The processing unit is also adapted to output further signals 29, e.g. for controlling the table, for controlling a navigation system, etc.

Fig. 3 shows a schematic representation of the path e.g. of the x-ray source on the C-arm along an alternating helical path.

The z-axis describes the movement of the C-arm in sideward direction. The x- axis and the y-axis define the plane of the roll movement of the C-shaped element with x-ray tube and x-ray detector along a circular arc. If both the movement in sideward direction and the roll movement of the C-shaped element are performed simultaneously, there results a helical path 50.

Due to mechanical limitations of the C-arm construction, the freedom of movement of the C-shaped element is limited, i.e. there is a first mechanical stop point 51 from which the roll movement has to be started and a second mechanical stop point 52 at which the roll movement has to be stopped. Therefore, it is not possible to perform a full roll movement over a range of 360° or more.

Therefore, it is necessary to reverse the roll movement direction of the C- shaped element when the mechanical limitation is reached in cases that an object of interest that is scanned by use of the C-arm system has a higher longitudinal length than the longitudinal length that can be covered with a single roll movement from the first mechanical stop point 51 to the second mechanical stop point 52 of the C-shaped element while the C- arm is performing the movement in sideward direction. It should be noted that in Fig. 3 the

stop point is drawn after 360°, whereas in the preferred embodiment the stop point is already reached after 180° plus fan angle).

The roll movement of the C-shaped element and the movement in sideward direction of the C-arm are started simultaneously. Following, the x-ray tube and the x-ray detector perform a movement along a helical path 50. Finally, the second mechanical stop point 52 of the C-shaped element is reached what means that the roll movement should be reversed. Anyway, the C-arm keeps on performing the movement in sideward direction.

The roll movement of the C-shaped element is reversed, and the C-shaped element continues its roll movement in opposite direction while the C-arm still keeps on performing the movement in sideward direction. Hence, the movement in sideward direction and the reverse roll movement of the C-shaped element result in a reverse helical path.

The continuous performance of movements along the helical path and the reverse helical path results in an alternating helical path, as depicted in Fig. 3.

Both the roll movement of the C-shaped element and the movement in sideward direction may comprise different kinds of movement types.

Before starting an examination procedure with an x-ray examination device according to the invention, the C-shaped element is in stop position, the roll movement velocity is zero. When started, the roll movement velocity is increasing until a certain velocity is reached. In due time before reaching the second mechanical stop point, the roll movement velocity is decreasing until the second mechanical stop point is reached. Then, while reversing the movement direction, the roll movement is briefly stopped. Afterwards, the roll movement velocity is increasing again.

During time periods of a higher roll movement velocity, the picture taking rate of the x-ray tube and x-ray detector may also be increased, whereas during time periods of a lower roll movement velocity the picture taking rate of the x-ray tube and x-ray detector may also be decreased.

Before starting the examination procedure with an x-ray examination device according to the invention, the C-arm is in stop position, the movement velocity in sideward direction is zero. When started, movement velocity in sideward direction is increasing until a certain velocity is reached. This movement velocity may be constant during the remaining examination procedure. At the end of the examination procedure, the movement velocity in sideward direction is decreasing until the C-arm is in stop position again.

During the reverse of the roll movement, it may be necessary to also adapt the velocity of the movement in sideward direction. Such a velocity adaption may comprise

decreasing and increasing the movement velocity in sideward direction. The movement in sideward direction may also be completely stopped when reversing of the roll movement, for example at the second mechanical stop point 52.

The picture taking rate of the x-ray tube and x-ray detector may be adapted depending on the changing movement velocity in sideward direction.

The velocity of each of the different movements may be changed continuously or gradually. The velocity, duration and magnitude of each of the different movements as well as the picture taking rate, tube voltage and tube current of the x-ray tube and the x-ray detector may be synchronized. It should be noted that the term "comprising" does not exclude other elements or steps and the "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.

LIST OF REFERENCE SIGNS:

2 C-shaped element

3 x-ray tube

4 x-ray detector

6 roll movement

7 guide rail

8 processing device

9 movement in sideward direction

10 table

11 table carrier

12 display unit

15 controlling unit

17 imaging device

19 motors

23 position sensors

25 user commands

27 other information

29 further output signals

30 first holder element

32 object of interest

34 second connecting point

36 L-shaped element

38 third connecting point

40 second holder element

50 helical path

51 first mechanical stop point

52 second mechanical stop point