Method for operating an X-ray device, X-ray device, computer program and electronically readable storage medium

A method is for operating an X-ray device. In an embodiment, the method includes acquiring a sequence of images of a patient; moving an acquisition arrangement including at least one X-ray tube assembly, during the acquiring of the sequence of images, along the patient in a scanning direction; evaluating at least two different images, showing at least one common feature of the patient, to determine depth information for the at least one common feature; and actuating a collimator aperture of a collimator of the X-ray tube assembly, as a function of position information describing a position of the acquisition arrangement in the scanning direction, to change an aperture angle of a radiation field generated by the X-ray tube assembly in the scanning direction.

PRIORITY STATEMENT

The present application hereby claims priority under 35 U.S.C. § 119 to German patent application number DE 102018212389.6 filed Jul. 25, 2018, the entire contents of which are hereby incorporated herein by reference.

FIELD

Embodiments of the invention generally relate to a method for operating an X-ray device, wherein a sequence of images of a patient is acquired and during the acquisition of the sequence of images an acquisition arrangement comprising at least one X-ray tube assembly moves along the patient in a scanning direction, wherein at least two different images showing the same feature of the patient are evaluated in order to determine depth information for at least one of the features; and to an X-ray device, a computer program and an electronically readable storage medium.

BACKGROUND

In order to investigate and diagnose orthopedic issues, X-ray images of a patient are often acquired which show a relatively long section of the patient's body, for example the vertebral column or a leg from the hip to the foot. Slot-scan radiography (SSR), for example, can be used for acquiring images of the type. In SSR, X-ray tube and X-ray detector are moved simultaneously along an axis of the patient while the X-ray beam is highly collimated into a slit. Owing to the strong collimation, i.e. because of the small aperture angle of the radiation field generated by the X-ray tube, the scattered radiation produced during the image acquisition is reduced, with the result that the patient is exposed to a smaller radiation dose compared to one or more composite standard radiographic images, while image quality is comparable.

A further scanning technique for acquisition of images of longer sections of the body is provided by parallel-scan tomosynthesis (PST). Compared with SSR, PST offers the advantage that a 3D tomosynthesis dataset can be generated by reconstruction, thereby enabling the overlapping of anatomical structures to be at least partially reduced. To that end, the collimator of an X-ray source is adjusted in such a way that a comparatively large aperture angle of the generated radiation field is produced. The image acquisition is then performed in such a way that as large an area of overlap as possible of the radiation field is obtained between the individual scans during an acquisition of a sequence of images. This enables 3D information to be generated during the scanning of anatomical features of the patient from different viewing directions. A method of such a type is described in U.S. Pat. No. 8,693,622 B2, for example.

SUMMARY

However, the inventors have discovered that compared with SSR, PST has a disadvantage that the patient is exposed to a higher radiation dose during the image acquisition due to the overlapping radiation fields.

At least one embodiment of the invention is therefore directed to an improved method for operating an X-ray device which enables images to be acquired with associated depth information while minimizing radiation exposure for the patient.

At least one embodiment of the invention is therefore directed to a method for operating an X-ray device, the method comprising:acquiring a sequence of images of a patient;moving an acquisition arrangement including at least one X-ray tube assembly, during the acquiring of the sequence of images, along the patient in a scanning direction;evaluating at least two different images, showing at least one common feature of the patient, to determine depth information for the at least one common feature; andactuating a collimator aperture of a collimator of the X-ray tube assembly, as a function of position information describing a position of the acquisition arrangement in the scanning direction, to change an aperture angle of a radiation field generated by the X-ray tube assembly in the scanning direction.

According to at least one embodiment of the invention, a collimator aperture of a collimator of the X-ray tube assembly is actuated in the scanning direction as a function of position information describing the position of the acquisition arrangement in order to change an aperture angle of a radiation field generated by the X-ray tube assembly in the scanning direction.

For an X-ray device according to at least one embodiment of the invention, it is provided that the device comprises a computing device and an acquisition arrangement, the acquisition arrangement comprising at least one X-ray tube assembly having a collimator and the computing device being configured for carrying out a method according to at least one embodiment of the invention.

For an X-ray device according to at least one embodiment of the invention, it is provided that the device comprises

an acquisition arrangement, including at least one X-ray tube assembly having a collimator; and

a computing device, configured toacquire a sequence of images of a patient;move an acquisition arrangement including at least one X-ray tube assembly, during the acquiring of the sequence of images, along the patient in a scanning direction;evaluate at least two different images, showing at least one common feature of the patient, to determine depth information for the at least one common feature; andactuate a collimator aperture of a collimator of the X-ray tube assembly, as a function of position information describing a position of the acquisition arrangement in the scanning direction, to change an aperture angle of a radiation field generated by the X-ray tube assembly in the scanning direction.

For a computer program according to at least one embodiment of the invention, it is provided that the program comprises instructions which, when executed by a computing device of an X-ray device, cause the computing device to carry out a method according to at least one embodiment of the invention.

For an electronically readable storage medium, it is provided according to at least one embodiment of the invention that a computer program according to at least one embodiment of the invention is stored thereon.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

According to at least one embodiment of the invention, a collimator aperture of a collimator of the X-ray tube assembly is actuated in the scanning direction as a function of position information describing the position of the acquisition arrangement in order to change an aperture angle of a radiation field generated by the X-ray tube assembly in the scanning direction.

A solution according to at least one embodiment of the invention offers an advantage that different anatomical structures and/or features of the patient can be imaged along the scanning direction using radiation fields expanded to different widths such that depth information relating to a feature shown in at least two images taken from different viewing angles can be obtained from the resulting images. At the same time, however, images can be acquired during the image acquisition in regions of the patient in which depth information is not necessary owing to the examination objective or the anatomical makeup of the region using a reduced collimator aperture and consequently a smaller aperture angle of the radiation field. This advantageously enables the radiation dose to which the patient is exposed to be reduced during the image acquisition in the regions, as well as, considered as a whole, for the entire acquisition of the sequence of images.

The method according to at least one embodiment of the invention therefore enables images to be acquired during an acquisition of a sequence of images of a patient along a scanning direction as a function of the position of the acquisition arrangement either using a radiation field with a wider aperture angle in order to obtain depth information or using a narrower radiation field in order to reduce the radiation dose. This advantageously enables images to be acquired using a radiation field with a wider aperture angle only in the regions in which depth information is also required subsequently, and to reduce the radiation exposure for the patient in regions in which depth information is not required.

The X-ray tube assembly of the X-ray device generates in particular a fan beam or a cone beam, wherein the aperture angle can be changed in the scanning direction, i.e. in the direction along which the acquisition arrangement moves during the acquisition of the sequence of images, by actuating the collimator of the radiation source.

In the process, the individual images of the sequence of images are generated in each case at different positions of the acquisition arrangement such that the images in each case visualize a different part or a different section of the patient. The degree of overlap between the individual sequentially acquired images is dependent here not only on the distance between the positions of the acquisition arrangement but also on the aperture angle, such that a large overlap between the scanned areas of individual sequentially acquired images can be used in regions in which depth information is to be generated, and the area of overlap can be reduced as far as possible in regions in which no depth information is required. A small area of overlap between individual sequentially acquired images can of course also remain in the regions in which no depth information is to be generated so that the images can subsequently be assembled into a composite image, for example by image stitching.

The relative positioning between the acquisition arrangement and the patient changes during the acquisition of the sequence of images. It is possible in this case that the acquisition arrangement moves along a stationary patient or that the acquisition arrangement is stationary and the patient is moved relative to the acquisition arrangement. A movement of patient and acquisition arrangement in such a way that the acquisition arrangement moves relative to the patient is also conceivable. The patient can be positioned in the X-ray device either upright or lying supine on a corresponding patient support and positioning device.

It can be provided according to at least one embodiment of the invention that the position information describes an anatomical position describing a current positioning of the acquisition arrangement in relation to the patient. The relationship between the spatial position of the acquisition arrangement, i.e. its position along an axis running in the scanning direction, and the anatomical position, i.e. the positioning of the acquisition arrangement in relation to the patient, can depend for example on the size of the patient and how the patient is positioned in the X-ray device. The position information can therefore advantageously describe the anatomical position of the patient such that the collimator aperture can be adjusted according to the region of the patient that is currently to be scanned. The possibility to set the collimator aperture of the collimator of the X-ray tube assembly as a function of the anatomical position in relation to the patient enables individual anatomical regions to be scanned in a targeted manner using a comparatively wider aperture angle in order to generate depth information, and other anatomical regions for which no depth information is desired or necessary to be scanned using a lower aperture angle in order to reduce the radiation dose.

During the scan of a leg of the patient from the hip to the foot, for example, the collimator can be adjusted in such a way that depth information is generated for at least one anatomical feature of the patient only in the region of a hip joint, a knee joint and an ankle joint, i.e. images are acquired in these regions using a greater aperture angle of the radiation field. In the other regions, in particular in regions having a less complex anatomical structure, images can be acquired with a smaller aperture angle in order to reduce the radiation dose.

Thus, in the example of the scan of the leg in the region of the thigh and the lower leg of the patient, a smaller aperture angle can be used since only single, non-overlapping bones are present there over a comparatively great length. Selecting for which anatomical features depth information is generated and for which such information is not, in other words how the collimator is actuated as a function of the anatomical position, can be decided individually for each acquisition of a sequence of images and according to the purpose of the examination.

In order to determine the anatomical position of the patient, it can be provided according to at least one embodiment of the invention that the anatomical position is determined from image data acquired via an optical camera of the X-ray device and/or that the anatomical position is determined from at least one already acquired image of the sequence of images. In this case the optical camera can be mounted for example on the acquisition arrangement and thus be movable with the acquisition arrangement or it can be arranged as stationary on the X-ray device.

The image data generated by the camera shows the patient or a part of the patient. The image data can in this case also indicate the position of the acquisition arrangement and in particular be realtime image data. It is also possible for the image data to be generated from the current position of the acquisition arrangement as viewing angle, in particular in the case of an optical camera mounted on the acquisition arrangement. The current anatomical position of the acquisition arrangement can subsequently be determined from the image data generated by the optical camera. A 3D camera, for example, can be used in this case as the optical camera.

It is equally possible for the current anatomical position of the acquisition arrangement to be determined from at least one already acquired image of the sequence of images. For this purpose, the anatomical structures to be identified on the image can for example be assigned to an anatomical position of the patient.

The anatomical position can be determined for example by way of software and/or by way of a computing device of the X-ray device. In this case the anatomical region of the image acquired with the following X-ray scan can be predicted for example by way of a realtime analysis of the most recently acquired X-ray images. This can happen e.g. taking into account an anatomical atlas and the known physical proportions of the patient and/or taking into account already existing X-ray images. It is of course also possible for the anatomical position to be determined based on a combination of an evaluation of the image data obtained with an optical camera and an evaluation of most recently acquired X-ray images.

In addition or alternatively thereto, it is possible for the anatomical position to be determined from a spatial position describing a current distance of the acquisition arrangement from a start point or an end point of its movement. For this purpose, it can be provided that an assignment of anatomical positions to the spatial positions in the scanning direction is performed for example as a function of patient size and/or the positioning of the patient in the X-ray device. If, for example, the size of the patient is known and the patient is supported in a defined position, then the anatomical position of the patient corresponding to the current spatial position can be inferred as a function of the current distance of the acquisition arrangement from a start point or an end point of its movement in the scanning direction.

It can be provided according to at least one embodiment of the invention that different anatomical positions are assigned to different spatial positions via a user input into a computing device of the X-ray device and/or via a manual moving of the acquisition arrangement into a spatial position corresponding to an anatomical position. The user input can be entered for example by an operator of the X-ray device. The association between the anatomical position of the patient and the spatial position can be established for example via a measurement of the patient and a subsequent input of the measured values obtained by the measurement. In addition or alternatively thereto, it is possible for the acquisition arrangement to be moved manually into a spatial position, the spatial position thus set then being assigned to a specific anatomical position of the patient by way of a user input into the computing device, such that the corresponding anatomical positions for one or more spatial positions are known for a subsequent measurement.

It should be noted that in addition to the variants described here it is also possible generally to use an existing registration of the patient or a registration that is to be performed with the X-ray device, in particular if suchlike is provided in any case. In this instance, for example, a model of the patient can be positioned in the coordinate system of the X-ray device in which the current spatial position of the acquisition arrangement or of the patient couch is also present. Beneficially, a registration will be correctively aligned in the event of movements of the patient.

According to at least one embodiment of the invention, it can be provided that an anatomical landmark is determined from at least one image of the sequence of images, at least one item of depth information being determined for the anatomical landmark. The at least one item of depth information can be determined from at least two images showing the anatomical landmark. It can also be provided that multiple items of depth information are determined for an anatomical landmark, for example in order to mark the course of an extended landmark, or that multiple landmarks are determined from the images of the sequence, for which depth information is determined. In particular it can be provided that the anatomical landmarks are determined from the obtained images automatically by a computing device of the X-ray device, in particular also taking into account an image analysis of acquired images of the sequence. It is of course also possible to determine an anatomical landmark from at least one image of the sequence of images without taking into account or determining depth information associated with the landmark, for example when the landmark is used for a subsequent 2D measurement.

In a preferred embodiment of the invention, it can be provided that the collimator aperture is assigned to an anatomical position as a function of assignment information stored in particular in a computing device of the X-ray device. Thus, information can be stored in the X-ray device to indicate with which collimator aperture for an anatomical position in the case of a majority of patients of a representative patient group good results are possible in terms of the generation of depth information and/or the determining of an anatomical landmark are possible with a satisfactory degree of precision.

According to at least one embodiment of the invention, it can be provided that the collimator aperture of the collimator of the X-ray tube assembly is actuated orthogonally to the scanning direction as a function of the position information in order to change an aperture angle of the radiation field generated by the X-ray tube assembly. By varying the angle of the radiation field orthogonally to the scanning direction, it is possible to align the image acquisition to a relevant width of the region that is to be scanned. In this way the radiation exposure of the patient can be reduced further. The lateral collimation, i.e. the variation of the aperture angle orthogonally to the scanning direction, can be performed in particular according to the angle parallel to the scanning direction as a function of the anatomical position. In a scan of the vertebral column of the patient, for example, the collimator aperture can be adjusted in such a way that the ribs of the patient adjoining the vertebral column at the sides are not encompassed in the scan.

According to at least one embodiment of the invention, it can be provided that at least one further acquisition parameter of the X-ray device is varied in addition to the collimator aperture of the collimator of the X-ray tube assembly, in particular a scanning speed of the acquisition arrangement and/or an X-ray focus-patient distance and/or an electrical voltage of the X-ray tube assembly and/or the tube current-time product of the X-ray tube assembly being used as acquisition parameters. An assignment of a value of the acquisition parameter to a specific anatomical position can also be stored in the X-ray device in respect of the at least one further acquisition parameter. This advantageously makes it possible for the individual images of the sequence of images to be acquired according to the current anatomical position of the acquisition arrangement. In this way, the best possible image quality can be achieved for each individual image of the sequence of images and/or the radiation exposure can be reduced to a minimum for the patient.

It can be provided according to at least one embodiment of the invention that an acquisition arrangement is used comprising at least one X-ray detector disposed opposite the at least one X-ray tube assembly, an acquisition parameter of the at least one X-ray detector being set as a function of the position information. This enables not only the X-ray tube assembly but also the X-ray detector to be adjusted as a function of a current anatomical position of the patient, as a result of which the image quality of an image showing the anatomical structure present in the current anatomical position can be further increased.

It can furthermore be provided according to at least one embodiment of the invention that a collimator aperture of a collimator of the X-ray detector and/or a detector entrance dose and/or an X-ray focus-detector distance and/or an angle formed by a central ray of the radiation field and a detector normal of the X-ray detector are/is varied as acquisition parameter(s) of the X-ray detector. By varying the collimator aperture of the collimator of the X-ray detector it is possible for example to exert an influence on a shielding of scattered radiation, as a result of which an improvement in image quality can be achieved. Also changing the detector entrance dose and/or the X-ray focus-detector distance can not only improve the image quality of one or more acquired images but also contribute to a further reduction of the radiation exposure of the patient that is to be examined. The angle between the central ray of the radiation field and the detector normal of the X-ray detector can be changed by tilting the X-ray tube assembly and/or by tilting the X-ray detector. Also in relation to the collimator aperture of the collimator of the X-ray detector as well as to the detector entrance dose, the X-ray focus-detector distance and the angle between central ray and the detector normal, it can be provided that a respective assignment of corresponding values as a function of the anatomical position is stored in the X-ray device.

According to at least one embodiment of the invention, it can be provided that a synthetic radiographic image which is supplemented with at least one item of depth information of a relevant anatomical region as additional information is generated from the sequence of images and/or that a 3D tomosynthesis dataset is generated from the sequence of images. The sequence of images can be presented to a physician for example in a clear and time-saving manner in the form of a synthetic radiographic image. A 3D tomosynthesis dataset produced from the sequence of images can be used for example to perform a forward projection at points for which depth information is available for a different viewing angle from the viewing angle of the acquisition of the sequence of images. Structures overlapping one another in the acquired images or in the two-dimensional synthetic radiographic image generated from the images can thus be visualized in a differentiated manner in accordance with the depth information. The viewing angle for the forward projection can in this case be chosen as a function of the depth information, so that for example a spatial separation of the anatomical structures can be represented in an optimal manner. It is of course also possible to perform a forward projection at points for which no depth information is available on the basis of the 3D tomosynthesis dataset generated from the sequence of image data.

In addition or alternatively thereto, a synthetic radiographic image can be produced from the 3D tomosynthesis dataset by not including certain anatomical regions in the forward projection. To that end, the anatomical structures are first segmented in the 3D tomosynthesis dataset and the structures that are not relevant can be masked out. In this way, the overlaying of anatomical structures can be reduced in the synthetic radiographic image. In a scan of the vertebral column of the patient, for example, the ribs of the patient can be segmented and masked out.

It is also possible for the depth information to be represented for example by color coding of one or more anatomical features in the radiographic image. In addition or alternatively thereto, a 3D tomosynthesis dataset that contains, at least for a part of the scanned region, a three-dimensional representation of the anatomical structures of the patient located there can also be generated from the sequence of images. Various generally known reconstruction methods that make use of scans having different viewing angles can be used for this purpose.

For an X-ray device according to at least one embodiment of the invention, it is provided that the device comprises a computing device and an acquisition arrangement, the acquisition arrangement comprising at least one X-ray tube assembly having a collimator and the computing device being configured for carrying out a method according to at least one embodiment of the invention.

For a computer program according to at least one embodiment of the invention, it is provided that the program comprises instructions which, when executed by a computing device of an X-ray device, cause the computing device to carry out a method according to at least one embodiment of the invention.

For an electronically readable storage medium, it is provided according to at least one embodiment of the invention that a computer program according to at least one embodiment of the invention is stored thereon.

All of the advantages and embodiments explained in relation to the method according to embodiments of the invention are also applicable analogously to the X-ray device according to embodiments of the invention, the computer program according to embodiments of the invention, and the electronically readable storage medium according to embodiments of the invention.

FIG. 1shows a schematic representation of an X-ray device1according to an embodiment of the invention. The X-ray device1comprises an acquisition arrangement2, which in turn comprises an X-ray tube assembly3as well as an X-ray detector4arranged opposite the X-ray tube assembly3. The X-ray device1further comprises a patient support and positioning device5, which in this example embodiment is embodied as a patient couch and on which a patient6is positioned. The X-ray device1also comprises a computing device7, which is connected to the X-ray tube assembly3and the detector4. The acquisition arrangement2is movable along a scanning direction, which is symbolized by the arrow8and corresponds to the z-axis of the coordinate system shown inFIG. 1.

The X-ray tube assembly3can be embodied for example as an X-ray tube and comprises a collimator9, which is implemented as adjustable. By adjusting the setting of the collimator9it is possible to vary the aperture angle10of a radiation field11generated by the X-ray tube assembly3. The aperture angle10in this case denotes the aperture angle of the radiation field11embodied as a cone beam field or fan beam field in the scanning direction, in other words, in the example shown, it determines the expansion of the radiation field11in the z-direction.

The acquisition arrangement2can be moved in the scanning direction along an axis12which runs from a start point13to an end point14. In this example embodiment, the length of the axis12corresponds to the longitudinal extension of the patient support and positioning device5, the start point13being oriented at the head end and the end point at the foot end14of the patient. It is of course possible that the movement of the acquisition arrangement also takes place the other way around and/or that the acquisition arrangement2moves along an axis12having a greater or smaller longitudinal extension. The movement of the acquisition arrangement2during an acquisition of a sequence of images can be controlled by the computing device7and be effected automatically.

What is to be understood as a spatial position of the acquisition arrangement2in the case of the X-ray device1shown inFIG. 1is the position of a lengthening of a central ray15of the radiation field11to the axis12. This position is indicated inFIG. 1by the arrow16. With the patient6positioned on the patient support and positioning device5, the spatial position can in this case be assigned an anatomical position identified by the arrow17. The anatomical position corresponds to the anatomical region of the patient6which can be scanned by the acquisition arrangement2in its current spatial position. In this case, analogously to the spatial position, the central ray15of the radiation field11generated by the X-ray tube assembly3is likewise made use of.

A method according to an embodiment of the invention for operating the X-ray device1provides that a sequence of images of the patient6is acquired while the acquisition arrangement2moves along the patient6in the scanning direction. During the acquisition of the individual images, the collimator aperture of the collimator9of the X-ray tube assembly2is adjusted as a function of position information describing a position of the acquisition arrangement2, i.e. the individual images of the sequence of images are therefore acquired with different aperture angles10, the size of the aperture angle10being dependent on the position information describing the position of the acquisition arrangement2in the scanning direction.

The effect of the aperture angle10on an acquisition of images is explained below in connection withFIGS. 2 and 3. For clarity of illustration reasons, the X-ray tube assembly3is shown in each case in only two positions17,18, which are spaced apart in the scanning direction and are arrived at one after the other in time in the course of an acquisition of a sequence of images. In the situation shown inFIG. 2, the collimator is set in such a way that a comparatively wider aperture angle10of the radiation field11results. Because of the greater expansion of the radiation field11it is possible to study two anatomical structures21,22arranged one above the other from different viewing directions, as is indicated by the dashed arrows23. As a result of the images generated from clearly different viewing directions, it is possible to produce high-quality depth information in relation to the anatomical structures21and22. For this purpose, the largest possible spatial overlap area24of the radiation field11from the positions17and18is desirable.

FIG. 3shows an image acquisition in the positions17,18using a smaller aperture angle10of the radiation field11. Because of the smaller aperture angle10, the spatial overlap area24is also reduced in size. Compared with the situation depicted inFIG. 2, the radiation exposure is reduced in the situation shown inFIG. 3because only a smaller area is irradiated by the radiation field11for each image acquired in the positions17and18.

FIG. 4illustrates a step in a method according to an embodiment of the invention. For the method according to an embodiment of the invention, it is provided that the aperture angle10of the collimator9of the X-ray tube assembly3is varied as a function of position information describing the position of the X-ray tube assembly3in the scanning direction. In this case the position information advantageously describes an anatomical position of the acquisition arrangement2, i.e. the positioning of the acquisition arrangement2in relation to the patient6.

An assignment of an anatomical position of the patient6to the spatial position of the acquisition arrangement2can be accomplished for example via a user input into the computing device7of the X-ray device3. For example, the measurements of the patient6can be taken by an operator of the X-ray device3prior to the acquisition of the sequence of images in order to enable the anatomical position of the positioned patient to be assigned to the spatial positions of the acquisition arrangement2.

It is also possible for a user of the X-ray device1to move the acquisition arrangement2manually and, when the spatial position coincides with an anatomical position, to store this assignment by way of a user input into the computing device7of the X-ray device3. In addition or alternatively thereto, it is possible for the anatomical position of the acquisition arrangement2to be generated from image data acquired via an optical camera25. In this case the optical camera25can be a part of the X-ray device1and be arranged either in a fixed location or as a component part of the acquisition arrangement2, for example in spatial proximity to the X-ray tube assembly3. For a current spatial position of the acquisition arrangement2, the corresponding anatomical position of the patient6can be determined from the images generated by the optical camera25, which is embodied for example as a 3D camera.

In addition or alternatively thereto, the anatomical position can also be determined from at least one already acquired image of the sequence of images. In the example embodiment described here, it is aimed to acquire a sequence of images showing a leg26of the patient6. Here, starting at a hip of the patient and extending down to the foot, nine anatomical positions P1to P9are schematically indicated as dashed lines.

FIG. 4shows the acquisition of an image in the hip region of the patient at position P1. Because of the spatially overlapping anatomical structures, such as the hip joint in the hip region of the patient6, depth information is desired in this region. The image acquisition by the acquisition arrangement2is therefore carried out at the position P1using a large aperture angle10of the radiation field11, i.e. a large collimator aperture is set for the collimator9of the X-ray tube assembly3.

FIG. 5illustrates a further method step in the method according to an embodiment of the invention, in which an image is acquired in the middle of a thigh of the patient6. Because there are no overlapping anatomical structures present when for example an image of a femoral shaft is acquired, no depth information is desired at the position P3in this example, so the scan is performed with a reduced aperture angle10at this point in order to reduce the radiation exposure for the patient6, i.e. the collimator9of the X-ray tube assembly3is therefore set to a small collimator aperture.

Different collimator apertures can therefore be used along the leg of the patient6for different positions P1to P9. The collimator apertures to be used in each case or, as the case may be, the depth information to be generated in each case can be stored here in the computing device7of the X-ray device1as a function of the anatomical position. It is also possible for a corresponding assignment of collimator apertures to anatomical positions to be input into the computing device7by a user of the X-ray device1prior to the commencement of the image acquisition or for the same to be selected from a plurality of possible assignments.

FIG. 6shows a diagram which plots the collimator aperture, in this case designated by the letter a, in the scanning direction, in this case along the z-axis. In addition to a maximum collimator aperture in the positions P1, P5and P9as well as the minimum collimator aperture in the region of the positions P3and P7, an intermediate value lying between the maximum collimator aperture and the minimum collimator aperture is set in this example at the positions P2, P4, P6and P8.

Referring to the example shown in the precedingFIGS. 4 and 5, images are therefore acquired using a large collimator aperture in the hip region (P1), in the knee region (P5) and in the region of the ankle joint (P9) of the patient, and using a minimum collimator aperture in the region of the thigh (P3) and of the lower leg (P7). In the transitional regions between maximum and minimum collimator aperture (P2, P4, P6and P8), a scan is performed using an intermediate value for the collimator aperture. The sequence of images acquired in the course of the method according to an embodiment of the invention can subsequently be processed and for example combined to construct a composite image.

It is of course possible for images to be acquired at a different number of positions and/or at positions different from those shown. It is also possible for no or more than one intermediate step of the collimator aperture to be chosen in order to obtain an aperture angle between maximum and minimum aperture angle10.

FIG. 7shows an overall image27produced from the sequence of images acquired via the method according to an embodiment of the invention. The overall image27represents a 2D radiographic image supplemented by the depth information and is composed of a plurality of single images28from the sequence of acquired images. The depth information can be highlighted in color, for example, or, as in this case, by different hatchings29. In this case the depth information can be indicated in particular in the regions that were previously acquired with a greater aperture angle10, such as the region of the hip (P1), the knee (P5) and the ankle joint (P9). In addition or alternatively to the 2D radiographic image, a 3D tomosynthesis dataset can be generated which contains a 3D model at least for some of the anatomical structures represented on the images.

It is possible to produce both a 2D radiographic image and a 3D tomosynthesis dataset. In this case the 2D radiographic image, for example, can be displayed to a user of the X-ray device, the user being able to select by way of a user input a region or an anatomical structure represented in the 2D image, a 3D representation of the selected region or of the anatomical feature generated from the 3D tomosynthesis dataset subsequently being able to be displayed to the user. Anatomical landmarks can also be determined in the representation generated from the sequence of images. Thus, for example, during the scan of a patient's leg, a plurality of landmarks can be used in order to check for the presence of genu valgum (knock-knees) and genu varum (bowlegs) via a measurement, such as a deviation of the Mikulicz line.

It is of course also possible to establish a different assignment of collimator apertures to anatomical structures from that described in the preceding example. For example, it may also be desired to generate depth information in the thigh region, for example in the event of a femoral fracture being present in this region, and in the surrounding regions, such as in the knee and the hip, for example, no depth information is necessary for the medical issue in question.

Although the invention has been illustrated and described in more detail on the basis of the preferred example embodiment, the invention is not limited by the disclosed examples and other variations may be derived herefrom by the person skilled in the art without leaving the scope of protection of the invention.

LIST OF REFERENCE SIGNS