DE102010020287A1 - Method for detecting position of investigation object during treatment of fracture, involves determining object position based on set of diagram parameter values determined around correspondence between acquired and virtual image data - Google Patents

Abstract

The method involves determining position of investigation object based on three-dimensional (3D)-volume data (21) and two-dimensional (2D)-image data (28,29) of investigation object. The virtual 2D-image data (48,49) from the 3D-volume data is determined based on diagram parameters. The virtual 2D-image data for several sets are determined by diagram parameter values of the diagram parameters to be determined around a correspondence between the virtual 2D-image data and acquired 2D-image data. The position of investigation object is determined based on one set of diagram parameter values. Independent claims are included for the following: (1) computer program for detecting position of investigation object; and (2) device for detecting position of investigation object.

Description

The invention relates to a method and a device for determining the position of an examination subject. In particular, the invention relates to a method and a device which permits a position determination as a function of pre-recorded three-dimensional (3D) volume data of the examination object.

Three-dimensional image or object detection is widely used in medical technology. 3D volume data are often used to prepare for therapeutic and / or surgical procedures. An example of an application is the trauma construction, for example for the treatment of bone fractures, in which further treatment steps can be planned on the basis of pre-recorded 3D volume data of the examination subject. When 3D imaging is performed at or just prior to therapy, and while the subject is already positioned for therapy, the location of the subject under examination is known upon acquisition of the 3D volume data. This allows the 3D volume data to be used directly for therapy. However, such in-situ 3D imaging may be undesirable for time reasons or due to the associated radiation exposure. For these reasons, it may be desirable to reuse pre-recorded 3D volume data of the subject later.

For a reliable use of pre-recorded 3D volume data, it may be necessary to determine a spatial allocation of the 3D volume data to the position of the examination subject at a later time, for example during an intervention. For example, for targeted therapy of a bone fracture whose location and history have been pre-recorded in 3D volume data, it may be necessary to relate the location of the examination subject to the 3D volume data prior to beginning an intervention.

One way to correlate 3D volume data with a location of the examination object at a later time is by the so-called registration using marks. One or more marks can be attached to the examination object. The marks, for example, different colored balls, are recorded with a stereo camera system. The position of the examination object is determined by an image analysis. Such a mark-based registration may require additional equipment, which may be undesirable for cost reasons. If necessary, the marks must remain attached to the object to be examined at well-defined positions for a longer period of time.

A method of tracking the movement of an examination object based on a 2D / 3D registration is described in US Pat DE 10 2004 004 603 A1 described.

The object of the invention is to specify a method and a device which allow the position of an examination subject to be related to pre-recorded 3D volume data. In particular, the invention has for its object to provide such a method and apparatus in which or in which the relationship between the position of the examination object with the pre-recorded 3D volume data can be dependent on 2D image data, without the position of the Detecting the 2D image data used data acquisition device relative to the examination object to know exactly.

The invention provides a method, a computer program and a device as defined in the independent claims. The dependent claims define preferred or advantageous embodiments of the invention.

In a method for determining a position of an examination object according to an aspect of the invention, a set of 2D image data representing the examination subject is detected with a data acquisition device. A position of the examination subject is determined depending on 3D volume data of the examination subject and the acquired 2D image data. To determine the positions, virtual 2D image data from the 3D volume data are computationally determined as a function of imaging parameters. The mapping parameters describe an image between voxel coordinate triplets of volume represented by the 3D volume data and pixel coordinate tuples of 2D image data. The 2D virtual image data is acquired for a plurality of sets of imaging parameter values of the imaging parameters to increase a match between the 2D virtual image data and the acquired 2D image data. The location of the examination subject is determined depending on at least one set of mapping parameter values.

In the method, the position of the examination object can be determined by a comparison of virtual 2D image data computationally determined from the 3D volume data and the actually acquired set of 2D image data. By choosing different sets of imaging parameter values, different positions and / or orientations of the volume represented by the 3D volume data can be tested out and thus the actual position of the examination subject in the acquisition of the 2D image data can be determined. Capturing a single set of 2D image data that represents exactly one 2D image of the examination subject may be sufficient for determining the location. However, it is not excluded that also several sets of 2D image data can be detected in order to determine the position of the examination subject at one time or several different positions of the examination subject at different times. Time can be saved and radiation exposure reduced compared to full 3D imaging. The position of the object can also be determined implicitly in the method, for example by storing the last set of mapping parameter values or variables derived therefrom.

The mapping parameters may include entries of a projection matrix. Projection matrices are a good way to describe mappings of voxel coordinate triples in pixel coordinate tuples in 2D X-ray imaging. The 2D virtual image data may be determined for the multiple sets of imaging parameter values by a radiographic projection. In this way, different positions of the volume represented by the 3D volume data can be mathematically simulated in the 2D X-ray imaging.

The location of the examination subject may be determined depending on a set of imaging parameter values for which the 2D virtual image data and the acquired 2D image data satisfy predetermined similarity criteria. Various similarity measures may be used, for example, cross-correlations, mutual entropy, mutual information, gradient cross-correlations, count rates of image signal differences, pattern intensities, and the like to verify compliance with similarity criteria. In this way, the similarity between the virtual 2D image data and the acquired 2D image data can be quantified. It is possible to determine those values of imaging parameters for which the 2D virtual image data and the acquired 2D image data agree well, in particular best. From these values, the position of the examination subject can be determined.

The plurality of sets of mapping parameter values may be determined to describe the mapping between the voxel coordinate triples and the pixel coordinate tuples for a plurality of different layers of the volume represented by the 3D volume data relative to a ray bundle. In this way, different layers of the volume can be tested relative to rays of a beam. The volume represented by the 3D volume data can, as it were, be translated and / or rotated relative to a radiation source and a detector of the data acquisition device in order respectively to determine the resulting virtual 2D image data and finally coincide as well as possible with the acquired 2D image data bring.

The plurality of sets of mapping parameter values may be determined such that the different layers differ in an orientation of the volume represented by the 3D volume data relative to a given beam, for example the central beam, of the beam. Alternatively or additionally, the different layers may differ in a lateral offset of the volume represented by the 3D volume data relative to the central ray of the ray bundle or to an image plane. Alternatively or additionally, the different layers may differ from the focus of the beam or the image plane at a distance of the volume represented by the 3D volume data. In this way, different layers of the volume represented by the 3D volume data can be tested, which correspond to the changes of relative positions that can be realized with different data acquisition devices.

At least one set of mapping parameter values may be determined depending on a user input. In this way, the user can control which different layers of the volume represented by the 3D volume data should be simulated.

The user input can take place via an input device of the data acquisition device. The change in the mapping parameter values resulting from the user input may be such that it corresponds to a change in the relative position and relative orientation between the examination subject and the data acquisition device resulting from this user input, which results when combined with the Input device, the operation of the data acquisition device is controlled. In this way, the user can intuitively test the parameter space with a controller known to him.

Alternatively or in addition to a user-defined variation of the mapping parameter values, in the iterative computational determination of virtual 2D image data, at least one set of mapping parameter values may be automatically determined. For this purpose, in one embodiment, depending on a comparison of the virtual 2D image data determined for a set of mapping parameter values with the acquired 2D image data, it can be automatically checked whether a predefined quality criterion is fulfilled. If the quality criterion is not met, for example, if a similarity measure between the acquired 2D image data and the virtual 2D image data determined for the set of mapping parameter values is less than a predetermined bound, another set of mapping parameter values may be automatically determined such that a similarity measure between the 2D virtual image data and the acquired 2D image data. This allows computer-aided automation in the determination of new values of the imaging parameters.

At least one mark may be provided on the examination object which is visible in the acquired 2D image data and the virtual 2D image data. Depending on a location of the mark in the acquired 2D image data and the virtual 2D image data determined for a set of mapping parameter values, a new set of mapping parameter values may be determined depending on a user input or automatically. Markers, such as implants, can leave strong signatures in the captured 2D image data that can be used to determine the location of the examination subject.

The captured 2D image data and the virtual 2D image data may be output via an optical output device. This allows a user to estimate the quality of the match achieved and / or make a user-defined change in the mapping parameter values.

The acquired 2D image data and the virtual 2D image data can be output simultaneously and coded, for example color-coded and / or polarization-coded, via the optical output device. For example, the captured 2D image data may be in a first color, e.g. Red, and the virtual 2D image data in a second color, e.g. B. green, are output. From the homogeneity of the hue resulting from an overlay, the user can estimate the quality of the achieved match.

Further 2D image data, which represent the examination object and are different from the 2D image data, can be acquired with the data acquisition device. Advantageously, the further 2D image data are acquired after a change in the relative position between the examination object and the data acquisition device. Additional 2D virtual image data may be computationally determined from the 3D volume data based on further mapping parameter values. The determination of the further mapping parameter values can be carried out as described above in such a way that several layers of the volume represented by the 3D volume data are tested out. By combining the results obtained from comparing the virtual 2D image data and the acquired 2D image data on the one hand and the other virtual 2D image data and the other acquired 2D image data on the other hand, the accuracy of the orientation can be increased. If the object to be examined has shifted uncontrolled between the acquisition of the 2D image data and the further 2D image data, the position of the examination object can be determined again by the acquisition of the further 2D image data.

From the virtual 2D image data and the other virtual 2D image data, a stereoscopic display can be generated. At the same time, a stereoscopic representation of the acquired 2D image data can be generated from the acquired 2D image data and the further acquired 2D image data. For this purpose, the further 2D image data are acquired after a relative rotation between the data acquisition device and the examination object by a predetermined angle. The further mapping parameter values, on the basis of which the further virtual 2D image data are determined, can be set to take account of the relative rotation, depending on the mapping parameter values on the basis of which the virtual 2D image data are determined. The stereoscopic representation of the 2D virtual image data and the captured 2D image data facilitates the user, on the basis of the depth information contained therein, to estimate the quality of the achieved match between virtual and captured 2D image data and / or to make user-defined changes to the values of the imaging parameters.

The further mapping parameter values can be determined as a function of the mapping parameter values used for the computational determination of the virtual 2D image data. If a change in the relative position between the examination object and the data acquisition device between the detection of the 2D image data and the further 2D image data is known, this change in the relative position can be described as Forced condition for determining the virtual 2D image data and the other virtual 2D image data are taken into account. Thus, the accuracy of the orientation can be increased.

A geometric distortion of the acquired 2D image data can be taken into account when comparing the acquired 2D image data and the virtual 2D image data. For this purpose, a distortion correction of the captured 2D image data can be performed. Alternatively or additionally, the virtual 2D image data can be computationally recorded. In this way, distortion effects can be taken into account when assessing the correspondence between virtual and captured 2D image data.

The data acquisition device may be a device for X-ray imaging or another image acquisition device, for example a photographic or ultrasound-based image acquisition device. By way of example, the data acquisition device may comprise an X-ray source and an X-ray surface detector. The data acquisition device can be designed as a C-arm device.

At least two sets of mapping parameter values may be determined such that the 2D virtual image data is determined for different layers of an X-ray detector relative to a radiation source of the data acquisition device. In this way, if the position of the X-ray detector relative to the radiation source is not known with high accuracy, different positions of the detector relative to the radiation source can be tested out.

According to another aspect of the invention, there is provided a computer program comprising a sequence of instructions that, when executed by an electronic computing device of a medical imaging device, cause the device to perform the method according to one aspect or embodiment of the invention. The computer program can be loaded, for example, into the memory of a control and evaluation computer of an imaging device, for example a C-arm system. The computer program may be present as source code or as a compiled instruction sequence. The computer program allows the device to be set up in a program to carry out the method.

The 2D image data can be detected using electromagnetic radiation, in particular optically. The virtual 2D image data may be computationally determined depending on the technique used to acquire the 2D image data. In particular, the virtual 2D image data can be determined in such a way that it is taken into account how voxel values of the 3D image data enter pixel values of the 2D image data depending on the technique used to acquire the 2D image data. For example, if the 2D image data is acquired with a camera sensitive in the visible spectral region of the electromagnetic spectrum, the 2D virtual image data is advantageously computationally determined from the 3D image data to represent an image of the surface of the examination subject. If infrared radiation is used to acquire the 2D image data, the penetration depth or location-dependent attenuation of this radiation in the examination object is correspondingly taken into account in the computational determination of the virtual 2D image data.

According to a further aspect of the invention, a data carrier is specified on which a computer program comprising a command sequence is stored which, when executed by a computing device of a medical imaging device, causes the device to carry out the method according to one aspect or embodiment of the invention. The data carrier can be, for example, a CD-ROM, a DVD, a magnetic tape, a flash memory or a USB stick, on which the computer program is stored as electronically readable control information. When this control information is read from the volume and executed by a computing device of the device, the method according to the various aspects or embodiments of the device may be performed automatically.

According to a further aspect of the invention, a device for detecting a position of an examination subject is specified. The apparatus comprises a detection device for detecting a set of 2D image data of the examination subject, a memory device for storing 3D volume data of the examination subject and a computing device. The computing device is coupled to the memory device and the detection device and configured to determine the position of the examination object as a function of the 3D volume data of the examination subject and the acquired 2D image data. The computing device is configured to computationally determine 2D virtual image data from the 3D volume data depending on imaging parameters describing an image between voxel coordinate triples of a volume represented by the 3D volume data and pixel coordinate tuples of 2D image data. The computing device is further configured to provide the virtual 2D image data for multiple sets determine mapping parameter values to increase a match between the virtual 2D image data and the acquired 2D image data, and to determine the location of the examination subject depending on at least one set of mapping parameter values.

The device allows to test different positions and / or orientations of the volume represented by the 3D volume data and thus to determine the actual position of the examination subject in the acquisition of the 2D image data. The device further allows to determine intrinsic parameters of the data acquisition device. Capturing a single set of 2D image data may be sufficient for determining the location. Compared to a new complete 3D imaging, time can be saved and radiation exposure reduced.

The apparatus may be arranged to perform the method according to one of the aspects or according to one of the embodiments.

Embodiments of the invention are suitable for determining the position of an examination object from pre-recorded 3D volume data and acquired 2D image data. Applications are in particular in medical technology.

Hereinafter, embodiments of the invention will be explained in detail with reference to the drawings.

1 is a schematic representation of a device according to an embodiment.

2 is a schematic representation of a portion of an examination object represented by 3D volume data.

3 is a schematic representation of captured 2D image data.

4 FIG. 10 is a flowchart illustration of a method according to an embodiment. FIG.

5 FIG. 12 is a schematic diagram for explaining determination of virtual 2D image data in the method of one embodiment. FIG.

6 is a schematic diagram for explaining the determination of virtual 2D image data with compared to 5 changed mapping parameter values.

7 is a flowchart representation of a method according to another embodiment.

8th FIG. 10 is a flowchart illustration of steps for determining a location of the examination subject. FIG.

The features of the embodiments described below may be combined with each other unless expressly stated otherwise.

In the following, embodiments of the invention will be described in the context of a 2D X-ray imaging. However, the methods and apparatuses according to embodiments of the invention may also be applied to other fields in which an assignment of pre-acquired 3D volume data of an examination subject to a position of the examination subject at a later time is to take place.

1 is a schematic representation of a device 1 for detecting the position of an examination object according to an embodiment. The device 1 includes a C-arm device 2 and a computing device 11 , The C-arm device 2 has a C-arm 3 on, which is mounted pivotably about at least one axis and to which an X-ray tube 4 and a detector opposite the X-ray tube 5 are attached. The x-ray tube 4 emits X-radiation, which is a volume, for example due to a ray cone 6 is defined, interspersed and detected by the detector 5 is detected. The detector 5 may be a planar detector. Examples of such detectors include so-called image intensifiers and camera systems or so-called flat panel detectors. A drive device 7 is operatively connected to the C-arm, so the C-arm 3 can be adjusted between a plurality of positions. A movement of the C-arm 3 is at 8th shown. The C-arm is in another Position with broken lines at 3 ' shown. Adjusting the C-arm 3 leads to a corresponding change in the volume penetrated by the X-ray radiation 6 ' , A patient table 9 supports an examination object P, for example a patient. A control device 10 controls the x-ray tube 4 , the detector 5 and the drive device 7 , While the device 1 schematic with a C-arm device 2 As shown, methods and apparatus according to various embodiments may also be performed with other data acquisition devices for capturing 2D image data.

The computing device 11 is with the C-arm device 2 connected. While the computing device 11 and the components associated with it 12 - 14 to illustrate the function are shown as separate elements, these elements can also be structurally in the C-arm device 2 be integrated. The computing device 11 is with an optical display device 12 coupled. The computing device 11 controls the display device 12 to display acquired 2D image data and / or computationally determined 2D virtual image data. The computing device 11 has a memory 13 on or is with the memory 13 coupled. In the store 13 3D volume data of the examination object P are stored. The 3D volume data can be obtained by various methods and devices for 3D imaging, such as computed tomography, filtered back projection (FBP) of a plurality of 2D X-ray images, magnetic resonance imaging, or other techniques. The 3D volume data can be determined before the examination object relative to the C-arm device 2 is positioned. For example, the 3D volume data can be determined in a preliminary investigation. For example, the 3D volume data may be stored as DICOM data.

The computing device 11 is set to get out of the store 13 stored 3D volume data to determine virtual 2D image data. The term "virtual 2D image data" here refers to 2D image data that is not determined by an actual 2D data acquisition, but computationally from the 3D volume data. The computing device 11 can determine the 2D image data as a so-called radiographic projection. Various methods for calculating radiographic projection from 3D volume data are known in the art. For example, with x-ray raycasting methods, the attenuation of x-ray radiation can be calculated according to Lambert-Beer's law along different rays passing through the volumes represented by the 3D volume data. Thus, computational virtual 2D image data can be determined. Such 2D image data are also referred to as digitally reconstructed X-ray images. Efficient methods for digital x-ray image reconstruction, for example using so-called light fields, are known and can be used by the computing device 11 be used. An example of an efficient technique for determining digitally reconstructed x-ray images is in Aodong Shen and Limin Luo, Point-based digitally reconstructed radiograph, 19th International Conference on Pattern Recognition, 2008. ICPR 2008. IEEE (2008), pp. 1-4 described. In further embodiments, alternatively or additionally, from the 3D volume data a surface representation can be computationally determined, which is suitable for being subsequently matched, for example, with a 2D optical image of the surface of the examination subject.

The 2D virtual image data depends on the location of the volume represented by the 3D volume data relative to an image plane and a beam focus in the digital X-ray image reconstruction. With position here the totality of translational and rotational degrees of freedom is called. The location of the volume represented by the 3D volume data relative to the image plane and the beam focus may be determined, for example, by the position of a volume center of the volume relative to the beam focus (three coordinates) and a rotation of the volume relative to a beam central beam (three angles) be. The location of the volume represented by the 3D volume data relative to characteristic points of a beam in the radiographic projection may be described by imaging parameters. Whenever reference is made to determining the location or outputting location-dependent information, it should be understood that the information about the location need not be in the form of Cartesian and angular coordinates, but is also implicit, for example, as a determined set of mapping parameter values can.

The imaging parameters determine in which pixel coordinate tuple of the determined 2D image data voxel coordinate triplets of the 3D volume data are mapped for a given position of the 3D volume data. The mapping parameters can be, for example, entries of a projection matrix. By changing values of the imaging parameters, virtual 2D image data can be obtained for several different layers of the volume represented by the 3D volume data. Thus, various positions and / or orientations of the volume represented by the 3D volume data relative to the x-ray source may be used 4 and the detector 5 of the C-arm device 2 be tested. The virtual 2D image data obtained for each of the layers can be compared with the acquired 2D image data. When a sufficient match between virtual 2D image data and acquired 2D image data, from the corresponding values of the imaging parameters, the position of the examination object P relative to the C-arm device 2 be determined. In this way, it is determined in which position the volume represented by the 3D volume data substantially coincides with the corresponding portion of the examination subject P in the detection of the 2D image data. Thus, a relationship between the coordinate system of the 3D volume data, the imaged examination object P in the data acquisition, and the coordinate system of the C-arm device 2 or other data acquisition device.

abgeleitet werden. Durch die Matrixelemente r1–r9 und t1–t3 wird eine Rotation bzw. Translation des durch die 3D-Volumendaten repräsentierten Volumens relativ zu einem Zentralstrahl eines Strahlenbündels bzw. einem Fokus des Strahlenbündels beschrieben. Die Matrixelemente p1–p3 beschreiben die perspektivische Projektion aufgrund der Abbildung in einem Strahlenkegel. Für den vorliegenden Fall der Abbildung von 3D nach 2D, also von Voxel-Koordinatentripeln nach Pixel-Koordinatentupeln, kann die Projektionsmatrix in homogenen Koordinaten auf eine 4×3-Matrix reduziert werden. Falls beispielsweise die Mittelachse des Strahlenkegels entlang der y-Achse gerichtet ist und der Detektor in einer zu der y-Achse senkrechten Ebene (x-z-Ebene) und in einem Abstand d vom Projektionszentrum liegt, kann die Projektionsmatrix M_i dargestellt werden als

The values of the imaging parameters may be selected depending on the data acquisition device used for data acquisition. For example, as in the device 1 When 2D X-ray imaging is performed, the mapping of voxel coordinate triplets of 3D volume data into pixel coordinate tuples of the 2D virtual image data can be well described by the elements of a projection matrix. In general, the projection matrix may consist of a 4 × 4 matrix of the shape (in homogeneous coordinates)

be derived. The matrix elements r1-r9 and t1-t3 describe a rotation or translation of the volume represented by the 3D volume data relative to a central ray of a ray bundle or a focus of the ray bundle. The matrix elements p1-p3 describe the perspective projection due to the image in a cone of rays. For the present case of mapping from 3D to 2D, voxel coordinate triples by pixel coordinate tuples, the projection matrix can be reduced in homogeneous coordinates to a 4 × 3 matrix. For example, if the central axis of the cone of rays is directed along the y-axis and the detector lies in a plane perpendicular to the y-axis (xz-plane) and at a distance d from the projection center, then the projection matrix M _i can be represented as

In general, the matrix elements of the projection matrix M _i are defined such that for a set i of virtual 2D image data v _{b, i} = M _i * v _v (3) applies. Here v _v = (x, y, z, w = 1) ^{T is} a column vector whose first three vector components represent the coordinate triplet (x, y, z) of a voxel of the 3D volume data. v _b = (r, s, t) ^T is a column vector, from which the coordinate tuple (u, v) of the pixel in the set of image data into which the voxel with the coordinates x, y and z is mapped, according to u = r / t and v = s / t can be determined. The index i denotes a set of mapping parameter values. Based on the equation defined by equations of the form (2) and (3), a volume rendering or a digital X-ray image reconstruction can take place.

Values of the mapping parameters can be changed in various ways. In one embodiment, the computing device 11 automatically determine a similarity measure for the virtual 2D image data and the acquired 2D image data. Various similarity measures can be used for this purpose, for example cross-correlations, mutual entropy, mutual information, gradient cross-correlations, pattern intensities and the like. Depending on the comparison, the computing device 11 Select new values for the mapping parameters to see if this will increase the match between the 2D virtual image data and the captured 2D image data. The selection of the new values for the imaging parameters can be done by systematically debugging the parameter space. Alternatively or additionally, the computing device 11 perform the new values for the imaging parameters using registration techniques, stochastic methods, or feature extraction in the 2D virtual image data and captured 2D image data. The position of the examination object can be recalculated from the imaging parameters for which an automatically determined similarity measure between the acquired 2D image data and the virtual 2D image data reaches a predetermined threshold value.

In a further embodiment, the values of the mapping parameters may be adjusted depending on a user input. This is the computing device 11 with an input device 14 coupled. The input device 14 allows the user to invoke a change in values of the extrinsic or intrinsic mapping parameters used to determine the 2D virtual image data. In this case, intrinsic parameters are the parameter components which the data acquisition device describes in itself. Examples of such intrinsic parameters are the focus detector distance or a tilt of the detector surface. Extrinsic parameters are the parameters which describe the position of the object to be examined P relative to the data acquisition device. In this case, the computing device 11 and the input device 14 be configured such that the change of the values of the imaging parameters in response to an operation of the input device 14 such is that they correspond to a translatory and / or rotational adjustment between C-arm device 2 and examination object P in response to the user input. It should be noted that the response to the operation of the input device 14 in the computational determination of the virtual 2D image data in an adjustment of the mapping parameter values, wherein the components of the C-arm device 2 or another data acquisition device but not actually be adjusted. The computational determination of the virtual 2D image data in response to the user input can be done using efficient methods in real time or approximately in real time. Here, a determination of the virtual 2D image data in real time is understood to mean that the computational determination for new values of the imaging parameters and a corresponding representation of the virtual 2D image data on the display device 12 keeping pace with the interactive operation of the input device 14 he follows.

The input device 14 has at least two degrees of freedom, for example six degrees of freedom. The input device 14 can have one or more moveable sections 15 . 15a exhibit. At least a section 15 can be hinged such that it can be tilted in two orthogonal directions. Several sections 15 . 15a of the input device can with a joint 16 be connected. The degrees of freedom of such an input device 14 however, as it may also be used as an input device to C-arm devices or other data acquisition devices, it allows for a user-intuitive method of changing the imaging parameters known from the operation of the C-arm device. For example, in one mode, moving at least one section 15 . 15a the values of the imaging parameters are changed so that this corresponds to a change in the orientation of the volume represented by the 3D volume data. Alternatively or additionally, by moving at least one section 15 . 15a the values of the imaging parameters are changed to correspond to a change in the position of a characteristic point, for example the volume center, of the volume represented by the 3D volume data. In this way changes of extrinsic parameter values can be tested. Alternatively or additionally, by moving at least one section 15 . 15a the values of the imaging parameters are changed to correspond to a change in the distance of the detector from the focus or another intrinsic parameter. In this way, values of the intrinsic parameters can be determined.

To facilitate a comparison of the captured 2D image data and the 2D virtual image data to a user, the computing device may 11 both the captured 2D image data and the virtual 2D image data in a superimposed representation via the optical display device 12 output. In this case, a suitable coding of the captured and virtual 2D image data can take place. For example, the acquired 2D image data may be displayed in a first color and the virtual 2D image data in a second color. A user can adjust the values of the imaging parameters by user input until the most uniform hue, but still with spatially varying intensity, results for the superimposed image. For example, the acquired 2D image data may be displayed in green and the virtual 2D image data may be displayed in red. By user input, the values of the imaging parameters and thus the virtual 2D image data can be adjusted until an overall image with a substantially gray hue is created. The output of the captured and virtual 2D image data via the optical display device 12 can also be done if the values of the imaging parameters at least partially automatically by the computing device 11 be set in order to allow a user to control the found values of the imaging parameters, and thus a control of the determined position of the examination subject.

In addition to the superimposed representation of the acquired 2D image data and the virtual 2D image data, the computing device 11 also determine a similarity measure of the captured and virtual 2D image data and the display device 12 output.

Regardless of whether the values of the mapping parameters are user - defined and / or automatically set, additional measures may be provided to determine the values of the Imaging parameters for which the 2D virtual image data and the acquired 2D image data match well.

Alternatively or additionally, one or more marks may be used which have a clear signature in the acquired 2D image data. The marks can be anatomical or non-anatomical. For example, an implant, for. A nail or a plate, on which portion of the examination subject P serve as a non-anatomical marker recognizable in the captured 2D image data. Based on the signature of the mark, the user-defined or automatic finding of the values of the imaging parameters, for which the virtual 2D image data closely approximates the acquired 2D image data, can be facilitated.

With the device 1 a position-dependent information can be determined, which consists for example of the set of mapping parameter values for which the best possible match between the virtual and captured 2D image data is achieved. This set of mapping parameter values may be used, for example, to provide a user with information about how a therapeutic instrument or diagnostic tool is positioned relative to the subject of the examination. For this purpose, the position of the therapeutic instrument or diagnostic instrument in a world coordinate system can be detected with a navigation system. Depending on the most recently determined set of mapping parameter values, the position of the instrument may be correlated with the pre-acquired 3D volume data and graphed, for example by suitable matrix multiplications, to facilitate navigation with the instrument.

2 is a schematic representation of a through 3D volume data 21 represented volume. The 3D volume data can be acquired with various examination modalities, for example using CT, magnetic resonance imaging, 3D X-ray imaging or the like. The 3D volume data represents a portion of the examination subject. Schematically illustrated is a limb, such as a thigh 22 with a bone 23 for example, a femur bone. The bone 23 has a break line 24 on. The voxel values of the 3D volume data can have different meanings, depending on the examination modality with which the 3D volume data was acquired. For example, if the 3D volume data were determined by X-ray, the voxel values may correspond to the Hounsfield values.

3 is a schematic representation of captured 2D image data 26 of the portion of the subject P. The 2D image data 26 show an image projected into an image plane 27 of the thigh 22 , an illustration 28 of the bone 23 and an illustration 29 the fault line 24 ,

With the devices and methods of various embodiments, from the 3D volume data 21 several sets of virtual 2D image data are computationally determined. The 2D virtual image data can each be captured with the acquired 2D image data 26 be compared. By changing mapping parameter values, for example by changing the elements of a projection matrix, different fictitious positions and / or orientations of the 3D volume data may be obtained 21 Volume tested relative to an X-ray source and an X-ray detector to be tested. This way you can use the 3D volume data 21 and the one set of captured 2D image data 26 the location of the examination object when capturing the 2D image data 26 be determined.

4 is a flowchart representation of a method 30 for determining the position of an examination object according to an exemplary embodiment. In the method, virtual 2D image data are computationally determined from previously determined 3D volume data. The 2D virtual image data is obtained for multiple values of imaging parameters to test different locations of the volume represented by the 3D volume data relative to a beam. The procedure 30 can from the device 1 be performed.

at 31 2D image data is captured. The 2D image data can be acquired with an X-ray area detector.

at 32 3D volume data of the examination object are read, which were acquired in advance. For example, the 3D volume data may be present as DICOM data. The 3D volume data may have been acquired with a suitable examination modality. In particular, the 3D volume data does not have to be acquired with the data acquisition device involved in capturing the 2D image data 31 is used. For example, the 3D volume data can be computed tomography, with a filtered Rear projection (FBP) of a plurality of 2D X-ray images, with a magnetic resonance tomography or other techniques are detected.

at 33 Values are initialized by mapping parameters. For example, a focus image plane distance to a predetermined value, e.g. B. 1100 mm, are set. The value for the focus image plane distance may vary depending on the distance actually set for image acquisition between the detector 5 and the X-ray source 4 the data acquisition device 2 which is used to acquire the 2D image data. The distance between the focus and the volume represented by the 3D volume data may be preset at one-half of the focus-image-plane distance. The values of the further imaging parameters can be preset such that a central ray of a ray bundle has a predetermined direction relative to the coordinate system of the 3D volume data, for example parallel to one of the coordinate axes of the 3D volume data, and through a predetermined point, for example the volume center, of the volume represented by the 3D volume data. If the location of the examination object can be estimated with a separate device, the initialization of the values of imaging parameters may be included 33 depending on the assessment of the situation. Unless here and in the context of the following steps of the procedure 30 a position of the volume represented by the 3D volume data relative to rays, a focus of a beam or an image plane is referred to, this refers to the computational determination of the virtual 2D image data. A change in the values of the mapping parameters must, and typically will not, be accompanied by an actual adjustment of components of the data acquisition device. Rather, different layers are computationally tested to perform a comparison with the one detected set of 2D image data.

at 34 From the 3D volume data, virtual 2D image data are computationally determined as a function of the values of the imaging parameters. Various methods can be used to computationally determine the 2D image data. For example, volume rendering can be used in which each voxel of the 3D volume data is projected in the direction of a line of sight onto a pixel of an image plane. A brightness value is integrated along the line of sight. From the 3D volume data, the attenuation of an X-ray beam along a line of sight can be calculated. The weakening when passing through a body or a voxel according to the law of Lambert-Beer according to I = I0 * exp (-μ * d), (4) where I is the intensity of the outgoing beam, I0 is the intensity of the incoming beam, μ is an attenuation coefficient and d is a penetration depth. By integrating equation (4) along a line of sight, a pixel value of a pixel of the virtual 2D image data can be computationally determined. In this case, the shading of two voxels lying one behind the other along the visual ray and the material property of each voxel are taken into account. In particular, the attenuation coefficient μ can vary as a material constant from voxel to voxel. For example, if the 3D volume data were determined using computed tomography methods or FBP of multiple sets of 2D image data, the voxel values indicate the Hounsfield values and can be used directly for radiographic projection. Alternatively or additionally, material-adapted look-up tables can be used to assign attenuation coefficients to the voxel values of the 3D volume data. This can be done in particular if the 3D volume data were determined, for example, using magnetic resonance tomography methods or other techniques which do not allow any direct conclusion as to the X-ray absorption properties of the respective material. Efficient methods for digital x-ray image reconstruction, for example using so-called light fields, are known and can be used 34 be used. An example of an efficient technique for determining digitally reconstructed X-ray images is in Aodong Shen and Limin Luo, Point-based digitally reconstructed radiograph, 19th International Conference on Pattern Recognition, 2008. ICPR 2008. IEEE (2008), pp. 1-4 described.

at 35 The captured 2D image data and the virtual 2D image data are output. The captured and virtual 2D image data may be output in color coded and superimposed to facilitate the user's verification of the match. For example, the captured 2D image data may be in a first color, e.g. Red, and the virtual 2D image data in a second color, e.g. B. green, are output.

at 36 It is checked whether a user input for changing the values of the imaging parameters takes place within a predetermined time. If yes, join 37 changes the values of the mapping parameters according to the user input, and the process returns 34 back. The user input at 36 can be done using the input device 14 the data acquisition or computing device done. Various user inputs may be received that allow the user to change the location of the volume represented by the 3D volume data relative to a beam. Changing the values of the mapping parameters 37 can be done such that in the computational determination of the virtual 2D image data one of the operation of the input device 14 corresponding position change of the examination object P is simulated relative to the data acquisition device, without the examination object P or the data acquisition device are actually moved in space. If, for example, an operation of the input device during normal operation of the data acquisition device to a translational displacement of the examination object P relative to the X-ray source 4 could lead to the values of the imaging parameters 36 and 37 be changed in response to this operation so that the virtual 2D image data for an equally translationally displaced position of the volume represented by the 3D volume data relative to a focus of the radiation beam are determined. Similarly, at 37 the values of the imaging parameters in response to an operation, which in normal operation, a relative rotation between the object to be examined P and data acquisition device 2 would be changed to simulate the corresponding rotation in determining the virtual 2D image data in real time.

If at 36 within a predetermined time, no user input occurs which results in a change in the values of the mapping parameters, or if so 36 a user input is made, indicating that the user is satisfied with the match of virtual and captured 2D image data, the method joins 38 continued. at 38 a position-dependent information is output. The position-dependent information is implicit in the last set values of the mapping parameters. For example, the last set of mapping parameter values may themselves be stored. The at 38 Information output can also be from those in the loop 34 - 37 determined values of intrinsic parameters of the data acquisition device depend. The information about the situation can be output in various ways.

For example, coordinates of a user-selected point of the 3D volume data relative to a laboratory coordinate system or coordinate system of the data acquisition device can also be determined and output. The output of the position information can, for example, also be such that the user is immediately informed of the position of the point he has selected, for example with an optical signal. In one embodiment, the X-ray device may be automatically positioned in response to the detected location such that the point selected by the user in the 3D volume data is mapped centrally and from a desired direction at the next data acquisition. In this way, for example, the X-ray device can be automatically positioned such that a break line is subsequently recorded in an orthogonal plan view. In one embodiment, the location of another instrument, such as a therapeutic instrument, may be detected in space. The output of the position of the examination subject can be made such that a relative position between the further instrument and the position of the user-defined point selected in the 3D volume data is determined and displayed. The user can position the further instrument at the location preselected by it in the 3D volume data by minimizing the output relative distance.

For practical application, in particular when using the devices and methods according to various embodiments in connection with therapeutic instruments, it may be advantageous to start from an additional third coordinate system, a so-called world coordinate system, to which everything is related. The patient lies in this world coordinate system. The location of therapeutic instruments is also defined in terms of the world coordinate system. A navigation system can be provided, with which the position of therapeutic instruments in the world coordinate system is detected. In the general case, registering establishes the reference of the 3D volume data to the world coordinate system. In embodiments, as exemplarily described, the 3D volume data may also be located directly in the world coordinate system. This can be accomplished by simultaneously defining the coordinate system of the 3D volume data as the world coordinate system.

With reference to 5 and 6 the apparatus and method of embodiments of the invention will be further described.

5 is a schematic diagram illustrating the digital X-ray image reconstruction from the 3D volume data of 2 illustrated. The determination of the 2D image data is carried out by summing or integrating brightness values along a plurality of beams of a radiation beam. The focus of the beam is at 40 shown. The beam has a plurality of beams 41 on. A device coordinate system is included 42 shown. The origin of the device coordinate system 42 is an example here in focus 40 , and the y-axis of the device coordinate system 42 represents the central ray 42a of the beam 41 dar. In an image plane 43 result in virtual 2D image data that is an illustration 48 of the bone 23 and an illustration 49 the fault line 24 exhibit. The virtual 2D image data differs from those schematically in the image plane 43 captured 2D image data representing the representation 28 of the bone 23 and the presentation 29 the fault line 24 exhibit. By testing out different orientations and / or positions of the volume through the 3D volume data 21 is represented, relative to the device coordinate system 42 For example, values of imaging parameters for which the captured 2D image data and the virtual 2D image data match well may be determined. To test the different layers of the volume 21 can the orientation of the volume 21 relative to the device coordinate system 42 be varied in the computational determination of the virtual 2D image data. For this purpose, values of imaging parameters can be changed in such a way that they produce different rotations of the volume-inherent coordinate system with the coordinate axes 45 - 47 relative to the device coordinate system 42 correspond. To test the different layers of the volume 21 can continue the position of the volume 21 relative to the focus 40 be varied in the computational determination of the virtual 2D image data. For this purpose, values of imaging parameters can be changed so that the distance 44 between the focus 40 and a volume center of the volume 21 and a transverse displacement of the volume 21 in the two directions transversal to the central ray 42a to be changed. Furthermore, a variation of values of the imaging parameters may be provided such that when determining the virtual 2D image data also different distances between focus 40 and image plane 43 and / or a tilt of the image plane 43 from the in 5 shown, to the central beam 42 orthogonal position can be simulated.

6 FIG. 12 is a schematic diagram showing the result of optimally superposing the actual 2D image data with the virtual 2D image data on the basis of the 3D volume data of FIG 2 illustrated. Compared to the in 5 The reconstruction shown was the orientation of the volume 21 relative to the device coordinate system used in 6 at 52 is shown, and a distance changed from a focus of the beam. The focus of the beam is at 50 shown. The beam has a plurality of beams 51 on. The central beam is at 52a shown. In an image plane 53 result in virtual 2D image data that is an illustration 58 of the bone 23 and an illustration 59 the fault line 24 exhibit. By a relative rotation of the beam relative to the volume 21 about 90 ° about an axis parallel to the axis 46 runs, and by reducing the distance between the focus 50 of the beam and the volume center of the volume 21 at a distance 54 a good match is achieved between the acquired 2D image data and the 2D virtual image data. In this case, for example, the respective bone contours 28 . 58 and the fault lines 29 . 59 in the picture plane 53 good for cover.

7 is a flowchart representation of a method 60 for determining the position of an examination object according to a further exemplary embodiment. In the method, virtual 2D image data are computationally determined from previously determined 3D volume data. The virtual 2D image data is acquired for multiple values of imaging parameters to test different locations of the volume represented by the 3D volume data relative to a beam. The testing of values of imaging parameters takes place automatically. The procedure 60 can from the device 1 be performed.

In the process 60 become at 31 2D image data captured at 32 pre-recorded 3D volume data read at 33 Values of mapping parameters initialized and at 34 virtual 2D image data determined from the 3D volume data depending on the values of the imaging parameters. These steps can be as with reference to 4 be described described.

at 61 For example, the virtual 2D image data and the acquired 2D image data are compared computer-aided. The comparison at 61 may include evaluating a similarity measure. Various known similarity measures can be used.

at 62 depends on the comparison 61 checks if the virtual and captured 2D image data satisfy a similarity criterion. Checking at 62 can compare one at 61 certain similarity measure with a threshold. If at 62 is determined that the captured and virtual 2D image data does not meet the similarity criterion are added 63 new values of the imaging parameters selected. The new values may be selected depending on a comparison of the virtual 2D image data and the captured 2D image data. For example, computer-aided feature extraction in the captured 2D image data and the virtual 2D image data may be performed to determine new values of the imaging parameters that result in greater similarity between the acquired and virtual 2D image data. Selecting the new values of the mapping parameters 63 may depend on the position of a brand in the virtual and captured 2D image data. After choosing the new values of the image parameters, the process returns 34 back.

If at 62 it is determined that the virtual and captured 2D image data satisfy the similarity criterion 38 position-dependent information issued. The step 38 can as with reference to 3 be executed described.

The referring to 3 described alteration of mapping parameter values depending on a user input and referring to FIG 6 Modification of imaging parameter values performed in a computer-assisted manner to test different layers may also be combined in methods and apparatuses according to further embodiments.

Both in the user-defined and in the automatic change of the mapping parameter values, the mapping parameter values can be changed so that different layers of the volume represented by the 3D volume data can be systematically and intuitively debugged, as with reference to FIG 8th will be described in more detail. In the case of a user-defined change of the values, the device or the method can be configured such that the user is provided with corresponding input possibilities for generating the named settings.

8th is a flowchart representation of method steps 70 which allow a systematic finding of mapping parameter values for which a good match with the acquired 2D image data is achieved. While a sequence of method steps are illustrated, the steps need not necessarily be performed in this order, and not necessarily sequentially. Steps can be repeated to further improve the match between virtual and captured 2D image data.

at 71 For example, the mapping parameter values are changed to test different orientations of the central beam of a beam relative to the volume represented by the 3D volume data. Such a change in the relative orientation is in 5 and 6 shown schematically. The choice of the orientation of the central beam can be made on the basis of a comparison of features in the acquired 2D image data and the virtual 2D image data. For example, the orientation of bones in captured and virtual 2D image data may be determined.

at 72 For example, the mapping parameter values are changed so that different shifts of the volume represented by the 3D volume data in the directions transverse to the central ray of the beam are tested out. In the schematic representation of 5 this corresponds to a displacement along the axes 45 and 46 , In the schematic representation of 6 this corresponds to a shift along the axes 46 and 47 , In this way, the transversal position of certain features of the examination object can be set in the virtual 2D image data.

at 73 For example, the mapping parameter values are changed to test different distances between a focus of the beam and a volume center of the volume represented by the 3D volume data. This essentially results in size scaling in the virtual 2D image data. Different focus-volume intervals are in 5 and 6 schematically at 44 and 54 shown.

With the steps 71 - 73 For example, the position of the volume represented by the 3D volume data relative to the beam describing the projection can be changed. With known location of the radiation source 4 and the detector 5 the device 1 from 1 Thus, the volume represented by the 3D volume data becomes, so to speak, relative to the radiation source 4 and the detector 5 Virtually shifted until there is sufficient matching between the virtual and captured 2D image data. The 3D volume data in the appropriate location is substantially coincident with the corresponding portion of the examination subject. In this way, a relationship is established between the actual position of the examination object and the 3D volume data.

Optionally available at 74 and 75 nor the values of the imaging parameters are changed so that different distances between the focus of the beam and the image plane and / or different orientations of the image plane are tested relative to a central beam of the beam. Typically, the testing of a small portion of the parameter space is sufficient here because the focus-detector distance and the orientation of the detector relative to a central beam are typically at least approximately are known. With steps 74 and 75 For example, the match between captured and virtual 2D image data can be further increased.

With reference to the figures, embodiments have been described in which the location of an examination object can be determined by comparing a plurality of sets of computationally determined virtual 2D image data with a single set of acquired 2D image data. The methods and apparatus can also be used for position determination when multiple sets of 2D image data are acquired. In one embodiment, multiple sets of 2D image data may be sequentially captured in time. With the procedures described with reference to the figures, the position of the examination object can be determined in each case. Thus, for example, during a therapeutic procedure, the position can be repeatedly determined, even if the examination object was moved uncontrollably between the various data acquisitions. In embodiments, the relative position between the examination object and the data acquisition device can also be changed in a controlled manner between the detection of different sets of 2D image data. For each of the sets of 2D image data, using the procedures described, values of imaging parameters can be determined such that the corresponding virtual 2D image data closely approximates the different sets of captured 2D image data. The values of the imaging parameters determined for the different sets of 2D image data can be merged to perform a higher accuracy orientation. In embodiments, 2D image data and other 2D image data may be captured so that they can be combined into a stereoscopic image. For this purpose, for example, a corresponding projection can be made in different eyes of the user. Associated 2D virtual image data and other 2D virtual image data may be determined, which may also be combined into a stereoscopic image. The depth information facilitates a user's verification of whether a desired match between captured and virtual 2D image data has been achieved.

While exemplary embodiments have been described in detail with reference to the figures, in further embodiments, modifications of these embodiments can be realized. While embodiments have been described in the context of C-arm devices, devices and methods in accordance with embodiments of the invention may also be used with other devices that capture a set of 2D image data or a few sets of 2D image data, and in which US Pat Location of the examination object to be determined.

Embodiments of the invention allow the determination of the position of an examination object depending on a set of acquired 2D image data and pre-acquired 3D volume data and provide current 3D information without having to resume the 3D volume data. Application fields exist, for example, in medical technology.

LIST OF REFERENCE NUMBERS

1

Device for determining the position

2

C-arm device

3

C-Arm

3 '

C-arm in another position

4

X-ray source

5

X-ray detector

6

cone beam

6 '

further radiation cone

7

C-arm drive

8th

Movement of the C-arm

9

patient table

10

control device

11

computing device

12

output device

13

memory device

14

input device

15

Section of the input device

15a

Section of the input device

16

joint

20

brand

21

3D volume data

22

thigh

23

bone

24

breakline

26

2D image data

27

Lower leg in captured 2D image data

28

Bones in captured 2D image data

29

Fracture line in captured 2D image data

30

method

31-38

steps

40

focus

41

Rays of a ray cone

42

Device coordinate system

42a

central beam

43

image plane

44

distance

45-47

Coordinate axes of the volume

48

Bones in virtual 2D image data

49

Fracture line in virtual 2D image data

50

focus

51

Rays of a ray cone

52

Device coordinate system

52a

central beam

53

image plane

54

distance

55-57

Coordinate axes of the volume

58

Bones in virtual 2D image data

59

Fracture line in virtual 2D image data

60

method

61-63

steps

70

method

71-75

steps

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102004004603 A1 [0005]

Cited non-patent literature

• Aodong Shen and Limin Luo, Point-based digitally reconstructed radiograph, 19th International Conference on Pattern Recognition, 2008. ICPR 2008. IEEE (2008), pp. 1-4 [0046]
• Aodong Shen and Limin Luo, Point-based digitally reconstructed radiograph, 19th International Conference on Pattern Recognition, 2008. ICPR 2008. IEEE (2008), pp. 1-4 [0066]

Claims (21)

Method for determining a position of an examination object (P), comprising: - acquiring a set of 2D image data ( 26 . 28 . 29 ), which represents the examination object (P), with a data acquisition device ( 2 ), and - determining the position of the examination subject (P) as a function of 3D volume data ( 21 ) of the examination object (P) and the captured 2D image data ( 26 . 28 . 29 ), characterized in that virtual 2D image data ( 48 . 49 ; 58 . 59 ) from the 3D volume data ( 21 ) depending on mapping parameters representing an image between voxel coordinate triplets of one through the 3D volume data ( 21 ) and pixel coordinate tuples of 2D image data are described, computationally determined, the virtual 2D image data ( 48 . 49 ; 58 . 59 ) for a plurality of sets of mapping parameter values of the mapping parameters to obtain a match between the virtual 2D image data ( 48 . 49 ; 58 . 59 ) and the captured 2D image data ( 26 . 28 . 29 ), and that the location of the examination subject (P) is determined in dependence on at least one set of mapping parameter values of the plurality of sets of mapping parameter values. Method according to Claim 1, characterized in that the imaging parameters comprise entries of a projection matrix, and in that the virtual 2D image data ( 48 . 49 ; 58 . 59 ) for the plurality of sets of mapping parameter values by a radiographic projection. Method according to claim 1 or 2, characterized in that the position of the examination subject (P) is determined as a function of a set of imaging parameter values for which the virtual 2D image data ( 48 . 49 ; 58 . 59 ) and the captured 2D image data ( 26 . 28 . 29 ) meet predetermined similarity criteria. A method according to any one of the preceding claims, characterized in that the plurality of sets of mapping parameter values are determined to match the mapping between the voxel coordinate triples and the pixel coordinate tuples for a plurality of different layers of the 3D volume data ( 21 ) represented volume relative to a beam ( 41 . 42a ; 51 . 52a ). A method according to claim 4, characterized in that the plurality of sets of mapping parameter values are determined such that different orientations and / or translational displacements of the 3D volume data ( 21 ) represented relative to a coordinate system ( 42 ; 52 ) of the beam ( 41 . 42a ; 51 . 52a ) and / or different orientations and / or translatory displacements of a detector ( 5 ) of the data acquisition device ( 2 ) relative to the coordinate system ( 42 ; 52 ) of the beam ( 41 . 42a ; 51 . 52a ) are tested. Method according to one of the preceding claims, characterized in that at least one set of mapping parameter values is determined depending on a user input. A method according to claim 6, characterized in that the user input via an input device ( 14 ), in particular via an input device ( 14 ) with at least six degrees of freedom, the data acquisition device ( 2 ) he follows. Method according to one of the preceding claims, characterized in that the virtual 2D image data (λ) determined for a set of mapping parameter values ( 48 . 49 ; 58 . 59 ) with the acquired 2D image data ( 26 . 28 . 29 ) to determine if the virtual 2D image data ( 48 . 49 ; 58 . 59 ) and the captured 2D image data ( 26 . 28 . 29 ) satisfy a predetermined similarity criterion and that automatically determining at least one further set of mapping parameter values if the predetermined similarity criterion is not met. Method according to Claim 8, characterized in that at least one mark (15) is applied to the examination subject (P). 20 ) that is visible in the acquired 2D image data and in the 2D virtual image data, and that the further set of imaging parameter values depends on locations of the at least one marker in the acquired 2D image data and those determined for the set of mapping parameter values virtual 2D image data is automatically determined. Method according to one of the claims, characterized in that the captured 2D image data ( 26 . 28 . 29 ) and the virtual 2D image data ( 48 . 49 ; 58 . 59 ) via an optical output device ( 12 ). A method according to claim 10, characterized in that the captured 2D image data ( 26 . 28 . 29 ) and the virtual 2D image data ( 48 . 49 ; 58 . 59 ) simultaneously and encoded, in particular color-coded and / or polarization-coded, via the optical output device ( 12 ). Method according to one of the claims, characterized in that further 2D image data representing the examination object (P) and of the acquired 2D image data ( 26 . 28 . 29 ) are different with the data acquisition device ( 2 ), and that further virtual 2D image data from the 3D volume data ( 21 ) are calculated based on further mapping parameter values. Method according to claim 12, characterized in that from the virtual 2D image data ( 48 . 49 ; 58 . 59 ) and the further virtual 2D image data a stereoscopic representation is generated. Method according to claim 12 or 13, characterized in that the further mapping parameter values depend on the computational determination of the virtual 2D image data ( 48 . 49 ; 58 . 59 ) mapping parameter values are determined. Method according to one of the preceding claims, characterized in that a geometric distortion of the acquired 2D image data ( 26 ) when comparing the captured 2D image data ( 26 ) and the virtual 2D image data ( 48 . 49 ; 58 . 59 ) is taken into account. Method according to one of the preceding claims, characterized in that the data acquisition device ( 2 ) is a device for X-ray imaging. A method according to claim 16, characterized in that at least two sets of mapping parameter values are determined so that the virtual 2D image data for different layers of an X-ray detector ( 5 ) relative to a radiation source ( 4 ) of the data acquisition device ( 2 ) be determined. Method according to one of the preceding claims, characterized in that the 2D image data are detected using electromagnetic radiation, in particular optically, and that the virtual 2D image data are determined by calculation as a function of the technology used to acquire the 2D image data. Computer program comprising a sequence of instructions which, when executed by an electronic computer ( 11 ) a device ( 1 ) for medical imaging the device ( 1 ) for carrying out the method according to one of claims 1-18. Device for detecting a position of an examination object (P), comprising: - a detection device ( 2 ) for capturing a set of 2D image data ( 26 . 28 . 29 ) of an examination object (P), - a memory device ( 13 ) for storing 3D volume data ( 21 ) of the examination object (P) and - a computing device ( 11 ) connected to the memory device ( 13 ) and the detection device ( 2 ) and is set up to determine the position of the examination object (P) as a function of 3D volume data ( 21 ) of the examination object (P) and the captured 2D image data ( 26 . 28 . 29 ), characterized in that the computing device ( 11 ) is adapted to virtual 2D image data ( 48 . 49 ; 58 . 59 ) from the 3D volume data ( 21 ) depending on mapping parameters representing an image between voxel coordinate triplets of one through the 3D volume data ( 21 ) and pixel coordinate tuples of 2D image data describe, computationally determine, wherein the computing device ( 11 ) is set up to display the virtual 2D image data ( 48 . 49 ; 58 . 59 ) for a plurality of sets of mapping parameter values to determine a match between the virtual 2D image data ( 48 . 49 ; 58 . 59 ) and the captured 2D image data ( 26 . 28 . 29 ) and to determine the location of the examination subject (P) in dependence upon at least one set of mapping parameter values of the plurality of sets of mapping parameter values. Device according to claim 20, characterized in that the device ( 1 ) is arranged to carry out the method according to one of claims 2-18.

Images