Computer-implemented method for operating x-ray device and x-ray device

Abstract

The invention relates to a method for operating an X-ray device, comprising a carrier, in particular a C-arm, and an adjusting device at least for moving the carrier for setting a projection geometry. The method comprises: providing a vascular model of a vascular structure of an examination subject, in which a target position of an instrument movable in the vascular structure is marked in the vascular model, providing an initial position of the instrument in the vascular structure of the vascular model, and providing a path from the initial position to the target position; specifying a support point along the path; in the optimization process of the target function by using the blood vessel model, the optimization trend of the projection geometric structure is determined aiming at the supporting points; wherein the objective function comprises at least one first term relating to optimization of the image content of the observer at the respective support point and at least one second term that minimizes the number of changes in the projection geometry along the path by movement of the carrier; and determining, for each projection geometry, an adjustment parameter for controlling the adjustment device.

Description

TECHNICAL FIELD

[0001] The invention relates to a computer-implemented method for operating an X-ray apparatus having a carrier on which an X-ray emitter and an X-ray detector are arranged opposite to each other and a regulating device for moving at least the carrier, in particular a C-arm, in order to set a projection geometry. Furthermore, the invention relates to an X-ray apparatus, a computer program and an electronically readable data carrier. BACKGROUND

[0002] For examinations and treatments of an examination object with the aid of an instrument in a vascular structure, it is generally the case that the instrument is guided through the vascular structure to a target position of the examination and / or treatment. Here, it is known to provide a monitoring of the movement progress by means of an X-ray apparatus which performs imaging. For example, a low-dose projection image, in particular a fluoroscopy image, can be recorded in a specific projection geometry, which is characterized, in the case of a C-arm X-ray apparatus, in particular by the projection direction or the angulation angle of the C-arm. Here, various possibilities have been described for a pre-processing of such a projection image in order to display it on an output device of the X-ray apparatus, for example by enriching the projection image with additional information. The pre-processing can also include generating a new pre-processed image on the basis of information determined from the projection image.

[0003] For example, for a patient as an examination object in a minimally invasive surgery, a catheter can be guided as an instrument through a section of a blood vessel in the vascular system to a target position, for example to a blood clot in the case of a stroke treatment or to a blood-supplying blood vessel in the case of an embolization treatment of a tumor. A two-dimensional real-time projection image can be used to visualize the catheter position, in particular also the blood vessel when a contrast agent is administered.

[0004] The two-dimensional projection image is generally recorded under the condition of a specific projection geometry, which can be suitably selected by a user, for example. In the case of a C-arm, the projection geometry is described mainly by its angulation, that is to say, in particular, by two angulation angles. Here, the personnel performing the surgery generally wishes to see the instrument and also the surrounding blood vessel, ideally the target position.

[0005] In the prior art, it is known in this respect to predefine a fixed angulation or projection geometry, which generally provides a sufficiently suitable solution for performing the surgery as a whole. For example, the anterior-posterior direction of the patient can be chosen as the projection direction.

[0006] In an improved approach, it is proposed to manually adjust the projection geometry by the user, for example the person performing the surgery and / or the technical assistant, in order to provide an ideal overview about the current situation of the surgery. However, this requires a certain amount of time, which can only be used in a limited range in minimally invasive surgery. Furthermore, each new setting interrupts the workflow of the intervention. Therefore, in interventions where such a manual setting is required, the projection geometry is often not adjusted, although this would enable a better visibility and a better assessment of the situation of the surgery. Furthermore, the collimation and the scaling factor, which can lead to a dose reduction, are often not chosen appropriately either. In many cases, frequent communication between the person performing the surgery and the technical assistant is also required in order to adjust the projection geometry. SUMMARY

[0007] The technical problem addressed by the present application is to give an aid for improved image support when performing a minimally invasive surgery in a vascular structure of an examination object, which still provides a significantly improved image quality in the course of the intervention, while the load on the user is as low as possible.

[0008] In order to solve the above-mentioned technical problem, according to the present application, a computer-implemented method, an X-ray device, a computer program and an electronically readable data carrier are provided. Advantageous refinements result from the following description.

[0009] The X-ray device has a carrier on which an X-ray emitter and an X-ray detector are arranged opposite to each other, and an adjustment device for moving the carrier, in particular a C-arm, in order to set a projection geometry. The computer-implemented method for operating an X-ray device according to the present application comprises the following steps:

[0010] providing a vascular model of a vascular structure of an examination object, which describes the course of the vessels in three dimensions, in particular by means of center lines, with which a projection image of the examination object can be recorded using the X-ray device, wherein a target position of an instrument, which can be moved in the vascular structure, is marked in the vascular model,

[0011] providing an initial position of the instrument in the vascular structure of the vascular model,

[0012] providing a path in the vascular structure of the vascular model from the initial position to the target position of the instrument,

[0013] specifying support points along the path,

[0014] - determining the course of the optimization of the projection geometry for the support points in the course of the optimization of the objective function under the condition of using the vessel model, wherein the objective function comprises, in addition to at least one first term relating to the optimization of the image content for the observer at the respective support point, at least one second term which minimizes the number of changes of the projection geometry along the path by the movement of the carrier, and

[0015] - determining the adjustment parameters for controlling the adjustment device for each projection geometry.

[0016] The carrier can particularly advantageously be a C-arm. C-arm X-ray devices are frequently used in vascular examinations and in vascular therapy, for example in angiography systems or in other ways in operating rooms. While many of the embodiments below relate to such C-arm X-ray devices, the application can also be applied to other types of carriers, for example to a carrier with a robot arm by means of which the X-ray detector and the X-ray radiator can be moved separately.

[0017] The examination object can be, for example, a patient, and the vessel structure can be a section of the vascular system of the patient, in particular a vessel tree. However, it is conceivable that the subject matter described here can also be used for interventions on workpieces, for example, which can have porous or other tubular structures.

[0018] According to the application, it is proposed to use a specific determinable input information, namely a three-dimensional vessel model of the relevant vessel structure with known target positions, in particular initial positions corresponding to the current positions at the time of determination and paths along the vessel of the vessel structure from the initial positions to the target positions, in order to ultimately determine the course of the projection geometry along the path in the optimization process. Here, however, the optimization is not only carried out with a view to the best recognizability of the relevant information for guiding the instrument in the vessel structure, but also with a view to the reduction of the changes of the projection geometry. This means that a suitable compromise is sought which, on the one hand, enables good recognizability of aspects which are important for navigation, but on the other hand enables a smooth progress of the operation without too many examinations. In other words, the number of projection geometries is preferably reduced in order to avoid continuous repositioning of the carrier and frequent mental reorientation of the personnel carrying out the operation. Since the course of the projection geometry can be determined automatically, no interaction of the user is required here either. By determining the adjustment information, it is also made possible to carry out an automatic adjustment when changing the projection geometry, so that the user is also relieved of a burden here.

[0019] This makes it possible to navigate the instrument to the target location with high quality and precision and to carry out the minimally invasive surgery, in particular to accelerate the minimally invasive surgery, quickly and as free of disturbances as possible. Furthermore, by efficient execution, it is also possible to keep the X-ray dose low and, in particular for the patient as the examination subject, to reduce the amount of contrast agent to be administered.

[0020] In the objective function, the at least one first term and the at least one second term are preferably provided with weighting factors. By means of such weighting factors, the influence of the respective optimization objectives can be appropriately selected. In embodiments, it can be provided that the weighting factors and / or their proportions are selected in dependence on a user input. Thus, the user can influence the optimization result in accordance with his preferences. A user who values a perfect perspective more can select a higher weight for the at least one first term, while a user who values a change in the projection geometry as little as possible can set a higher weight for the at least one second term.

[0021] As optimization parameters, it is possible to use geometric parameters which describe the projection geometry at the respective support points. The optimization parameters can in particular describe, for each support point, at least one angle of the C-arm, i.e. its angulation. Preferably, both angles of the C-arm are used. If the translational position of the C-arm can be influenced by means of an adjustment device and / or manual intervention, a further optimization parameter can describe the translational position of the C-arm. In addition to a mere adjustment of the carrier, as will be discussed in detail below, it is also possible to optimize the zoom and the collimation together in the optimization process. Correspondingly, the optimization parameters can also be collimation parameters and / or zoom parameters.

[0022] By means of the adjustment parameter set for the adjustment device, the adjustment device can be directly controlled to set the corresponding projection geometry. With the arrival at a support point at which a change takes place, in particular after a user confirmation, the projection geometry can be set directly. That is to say, the method makes it possible to optimally prepare the further course of the minimally invasive surgery.

[0023] In an embodiment it can be provided that the vessel model to be provided is determined from a three-dimensional image data set of the examination object, which is registered with the coordinate system of the X-ray device, or that the three-dimensional image data set of the examination object is registered with the coordinate system of the X-ray device. For determining the vessel model, in particular trained analysis functions can be used, which can determine a center line and / or a boundary of the vessel. Such analysis functions are largely known in the prior art and can work, for example, together with a segmentation. Here, the three-dimensional image data set can be recorded with a carrier, for example by rotating the recording device itself consisting of an X-ray emitter and an X-ray detector (for example as a C-arm CT) around the examination object, or it can also be recorded before the intervention, i.e. before the procedure with the instrument. The three-dimensional image data set can be, for example, a magnetic resonance image data set and / or a computed tomography image data set. If the three-dimensional image data set is not recorded with the X-ray device, or was recorded before a repositioning of the carrier and / or the examination object, which cannot be tracked by sensors, a known 2D-3D or 3D-3D registration technique can be used, for example, to achieve a registration of the three-dimensional image data set and thus also of the vessel model with the coordinate system of the X-ray device.

[0024] In particular, the three-dimensional image data set can also be used in the planning phase, if necessary in combination with the vessel model, as is known in principle, in order to select the target positions there (and thus also in the vessel model) manually and / or automatically. An at least partially automatic determination of the target positions is also conceivable, for example by detecting thrombi or tumors and / or by flow simulation, in particular when embolization therapy is carried out.

[0025] In a preferred development it can be provided that the initial position is determined from at least one current two-dimensional projection image, in particular a perspective image, of the projection geometry, in particular under the condition that additionally a vessel model and / or a three-dimensional image data set is used, and / or under the condition that a tracking system of the X-ray device is used. For example, as is known in principle, the current position of the instrument can be tracked in real time in a two-dimensional perspective image. If a registration has not yet been made, this two-dimensional representation of the instrument and the vessel structure can be registered with the three-dimensional representation of the vessel structure, i.e. the vessel model. In this case, however, but also in the case where a registration has already been established, the motion of the patient, in particular periodic motions such as the heartbeat and / or the breath, can be taken into account accordingly. Furthermore, in the search for the position, it can be taken into account that the instrument is connected inside the vessel structure. In any case, the result is the current three-dimensional position of the instrument, which is the initial position in the initial situation to be evaluated for the optimization process. Alternatively or additionally, however, it can also be provided within the scope of the application that the X-ray device has a tracking system for determining the current three-dimensional position of the instrument. Here, tracking techniques known in principle in the prior art can be used, for example electromagnetic tracking, optical acoustic tracking, etc. Finally, it is also possible to start from a planned initial position, for example a branch to the vessel tree leading to the target position, etc. Such an initial position can be marked in the vessel model like the target position.

[0026] Various methods can be used to determine the path, in particular suitable path finding functions can be used which can find a path between two points in the vessel structure. For example, it can be provided that the path is determined as the shortest connection through the vessel structure from the initial position to the target position. However, boundary conditions can also be used here, for example a required specific size of the vessels to be used, etc. In vessel trees in which there are no malformations in the vessel system of the patient, it often even makes sense for only one possible path to have to be found by the path finding function.

[0027] For the selection of the support points, the preferred design of the application provides that the support points are specified at least at nodes of the vascular structure at which a plurality of vessels meet, in particular at bifurcations, and / or that the support points are selected at least partially at regular intervals along at least one center line of a vessel or vessel segment of the path. Suitably, a suitable projection geometry can be determined at least for positions at which a plurality of possibilities for further guiding the instrument exist due to branching, in particular for bifurcations. In particular at bifurcations, in order to be able to further guide the instrument without error, gently and accurately, it is extremely important to obtain a good overview of the overall situation, so that suitable information can be provided purposefully by the method presented here. Further support points can also be specified between nodes. The support points can be specified at regular intervals between bifurcations, but also in dependence on the characteristics of the vascular structure, for example at narrow curves. For regular intervals, an interval in the range of 1 to 5 mm can be selected, for example.

[0028] At least one of the at least one first item can be selected from the group comprising:

[0029] - for support points at and / or within a certain tolerance range around bifurcations of the vascular structure, an item for minimizing the deviation of the projection direction of the projection geometry from the direction of the course of the vessel at the bifurcation, in accordance with the vessel model,

[0030] - in particular for support points which are not at bifurcations and / or which lie outside the tolerance range, an item for minimizing the apparent shortening of at least the vessel in which the support point lies and / or of all vessels of the path from the support point to the target position which are visible in the projection geometry, in particular in a manner which weighs less with increasing distance from the support point in the vascular structure,

[0031] - an item for facilitating the visibility of the respective support point in the center of the projection image recorded using the projection geometry,

[0032] - an item for maximizing the visible length of the vessel along the path from the support point to the target position,

[0033] - an item for minimizing the dose load of the examination object and / or of at least one treatment person and / or of an operating person, and

[0034] - an item for minimizing the occlusion of at least a portion of the vascular structure, in particular of the support point and / or of the path from the support point to the target position, by other structures of the examination object, in particular by bone.

[0035] Therefore, at the bifurcation point, it is particularly expedient to minimize the deviation of the projection direction of the projection geometry from the cross product of the orientation direction of the vessel or vessel segment of the bifurcation point. In other words, for the branch, the cross product between the straight lines fitted to the vessels can give the preferred viewing direction / projection direction, since these vessel segments are parallel to the image plane of the two-dimensional projection image and can be well resolved and perceived. Deviations from this optimal projection direction can be evaluated, for example, in the objective function using a penalty cost.

[0036] In particular outside the support point, the visual foreshortening of the vessel, in particular the visual foreshortening of the vessel in connection with the guidance of the instrument, can be minimized. This can relate to the vessel or vessel segment in which the support point is located, but also to a plurality of vessels along the path or even to all vessel segments along the path up to the target position. Here, on the one hand, it can be envisaged that the visual foreshortening is weighted less with increasing distance from the support point in the vessel structure. On the other hand, however, in particular in the case of the administration of contrast agent, the entire path up to the target position can be relevant, so that the weightings can also be chosen identically along the entire path when the contrast agent is administered.

[0037] Since the user generally wishes the instrument to be located in the center of the image, the first term can also contribute to the visibility of the instrument in the center of the projection image recorded with the projection geometry. Here, for example, an acceptable central region of the instrument can be defined. This can also be achieved within the scope of the boundary conditions.

[0038] The visible length of the vessel along the path from the support point to the target position can also be maximized by means of a suitable first term. This can be used as an addition or an alternative to the minimization of the visual foreshortening. Thus, the projection geometry of the entire remaining path from the support position to the target position can be striven for to be optimally displayed. This is particularly expedient for contrast agent injection, since the contrast agent injection is not only relevant in the immediate surroundings of the instrument.

[0039] The purpose of a further first term can be to minimize the dose load, more precisely to minimize the dose load for the examination object and for at least one treatment and / or operating person. A specific arrangement of the X-ray radiator and the X-ray detector, for example, leads to a higher dose load for the examination object, in particular also for the user, i.e. in particular the person performing the procedure (treatment person) and / or the technical assistant person (operating person). By means of a corresponding first term, such an arrangement can be avoided. Here, not only dose models which take into account, in particular also, scattered radiation, etc. can be used, but also dose distributions which are predefined or known for a specific projection geometry, for example in a look-up table, etc. Corresponding methods are known, for example, from dose monitoring and can also be used within the scope of the optimization process.

[0040] Furthermore, it is conceivable to additionally or alternatively use terms which minimize the occlusion of at least a portion of the vessel structure, in particular of the instrument and / or of the path from the support point to the target position, by other structures of the examination object, in particular by bone. That is, if there are structures in the examination object which produce a stronger occlusion, for example in the case of a patient the bones, which can limit the image quality in terms of the guidance of the instrument, the optimization process can also avoid such cut-offs by suitable first terms, for example by positioning the spine in the radiation path to or from the instrument or the path. Information about the position of the occluding structures can be obtained, for example, from the already mentioned three-dimensional image data set.

[0041] For the second term, it is preferably possible to determine a change in the projection geometry from one support point to the next support point depending on a change in at least one adjustment parameter of the carrier, in particular a change in its angulation angle. If, for example, two angulation angles of a C-arm are used, a change can be identified in particular when at least one difference in the projection angles of adjacent support points is unequal to zero. The second term can comprise, for example, a corresponding mathematical expression about the number of such changes.

[0042] The second term can be selected in proportion to the number of changes in the projection geometry along the path. In this way, in particular a simple algorithmic implementation can be realized which exhibits the essential aspects (number of changes in the projection geometry along the path) and which, for example, introduces the objective function correspondingly with these increased penalty costs. However, a suitable design can also be provided which weights each change in the projection geometry with the strength of the change. Changes which, for example, exhibit only a small correction can thus be associated with a smaller penalty cost than changes which, for example, lead to a longer and / or more complex adjustment process. Thus, ultimately a shorter adjustment path can also be favored and thus further contribute to the efficiency. Here, the strength of the change can be described by a distance measure of the projection geometry, for example a corresponding difference in the angulation angle, but also the actually required adjustment path of the carrier can be taken into account.

[0043] Suitably, at least one collimation parameter and / or scaling parameter can also be determined for each projection geometry, the collimation parameter describing the collimation of the projection image to be recorded, the scaling parameter describing the scaling of the projection image to be recorded. Here, the further first term and / or third term of the objective function and / or the further discussed boundary conditions can also at least partially relate to the collimation and / or scaling, for example as a penalty term when at least one element from the group consisting of: the medical instrument at the support point, the vessel segment of the path on the path from the support point to the target position and the target position is not imaged. Here, a more distant vessel segment can lead to a smaller penalty value than a closer vessel segment.

[0044] It is preferred to use at least one boundary condition as a boundary condition term of the objective function and / or as a term to be checked additionally. Such boundary conditions (English: Constraints) are known in principle for optimization problems and can for example relate to technical limits of the X-ray device, to targets of the two-dimensional projection imaging to be fulfilled compulsorily, etc. For example, it can be specified that at least one of the at least one boundary condition is selected from the group consisting of:

[0045] - a predefined arrangement of the X-ray detector above the examination object,

[0046] - a collision-free movement path between the two projection geometries,

[0047] - a visibility of the path to the target position for each projection geometry, and

[0048] - at least one limit given by the design of the X-ray device.

[0049] By arranging the X-ray detector above the examination object, it is ensured that the X-ray radiator is arranged below the examination object and thus in particular below the object table, in particular the patient table, of the X-ray device, so that a reduction of the radiation load of the user can also be achieved in this way. The collision-free movement path between the two projection geometries can for example be checked by means of a collision protection system of the X-ray device. For example, a collision protection system can be interrogated as to whether a collision-free movement is possible. In this way, it can be ensured that a change can be made. If the user, in particular the personnel performing the surgery, wishes to see a particular aspect in each projection image, for example the entire path up to the target position in addition to the instrument, suitable boundary conditions can also be defined. Finally, as already mentioned, technical limits of the X-ray device itself can also be taken into account by means of the boundary conditions. It should generally be noted that the boundary conditions can also be integrated into the objective function as penalty terms.

[0050] In summary, it is thus possible that there are high-dimensional non-convex optimization problems with boundary conditions, which can be solved by suitable solution algorithms in order to find the optimal course of the projection geometry through the support points. Here, it can be provided in an exemplary advantageous design that the optimization process is carried out using a Viterbi algorithm and / or a forward-backward algorithm. Such solution algorithms have the advantage that a global optimum can be found, but require the use of discrete values of the optimization parameters. In one example, with respect to the angulation angles with support values, the optimization parameters can work in intervals of, for example, 1° to 10°. However, other solution algorithms known in principle from the prior art, for example gradient-based methods, can also be used.

[0051] In order to implement the image monitoring in a simple manner using the determined adjustment information, it can be provided that the current position of the instrument in the vessel structure is tracked, wherein, upon reaching a support point at which a change of the projection geometry according to the optimized course takes place, in particular after a user confirmation, the adjustment device is controlled by means of the adjustment parameter set of the projection geometry to be newly set.

[0052] Here, it should also be noted at this point that the method according to the application only relates to the operation of the X-ray device and the settings of the X-ray device for recording the projection images. It does not include the surgery itself nor the administration of contrast agent, if provided.

[0053] As already described, the current position of the instrument can be continuously tracked, for example by means of an evaluation of the two-dimensional projection images, in particular perspective images, and / or by means of a tracking system. That is, the reaching of a support point, and thus also the change of the projection geometry in the optimal course, can be recognized. It can then always be provided that the user is proposed the new projection geometry. If the user agrees to the new projection geometry, that is, if the user accepts the new setting, the new projection geometry can be automatically set by means of the adjustment information. In this case, in order to monitor the guidance of the instrument, very suitable two-dimensional projection images can be recorded as required.

[0054] In this, in a particularly expedient expansion it can be provided that the user-side confirmation is carried out together with the release of the X-ray radiation and / or when the operating foot pedal is operated. In this way, the user does not need to use a different operating device than he would otherwise use for releasing the X-ray radiation and for recording the projection images, and because the operating device is operated with the foot, it causes a smaller deflection of the examination object. It is also conceivable that the operating is used to accept a new projection geometry and to release the recording of at least one two-dimensional projection image in this new projection geometry. Thus, the number of interactions with the X-ray device is also reduced.

[0055] Furthermore, one expedient expansion can provide that, when a projection geometry deviating from the optimized course is set on the user side, a new determination is carried out according to the optimization process on the basis of the set deviating projection geometry. This means that, when the user has set the carrier in a different way than recommended according to the optimized course, in particular a renewed determination of the optimized course can be carried out in real time on the basis of the projection geometry selected on the user side. Thus, the deviating setting and the user's wishes can be taken into account, but an excellent support is provided in the further course.

[0056] In addition to the method, the invention also relates to an X-ray device having a carrier, on which an X-ray emitter and an X-ray detector are arranged opposite one another, an adjustment device for at least moving the carrier in order to set a projection geometry, and a control device, wherein the control device has:

[0057] - a first interface for providing a blood vessel model of a blood vessel structure of an examination object, which blood vessel model describes the course of the blood vessels in three dimensions, in particular by means of center lines, with which projection images of the examination object can be recorded using the X-ray device, wherein a target position of an instrument that can be moved in the blood vessel structure is marked in the blood vessel model,

[0058] - a second interface for providing an initial position of the instrument in the blood vessel structure of the blood vessel model,

[0059] - a third interface for providing a path in the blood vessel structure of the blood vessel model from the initial position to the target position of the instrument,

[0060] - a specification unit for specifying support points along the path, and

[0061] - a determination unit for determining, in the course of the optimization of the objective function under the condition of using the vessel model, for the support points an optimized course of the projection geometry, wherein the objective function comprises, in addition to at least one first term relating to the optimization of the image content for the observer for the medical instrument located at the respective support point, at least one second term which minimizes the number of changes of the projection geometry along the path by the movement of the carrier, and the determination unit is for determining, for each projection geometry, an adjustment parameter for controlling the adjustment device.

[0062] All implementations with respect to the method according to the application can be transferred analogously to the X-ray device according to the application and vice versa, so that the recognized advantages can also be achieved with the X-ray device according to the application. The control device can have at least one processor and at least one storage device. The functional units of the control device can be formed by hardware and / or software.

[0063] Here, the interface can also be at least partially an internal interface. Thus, the control device can for example also have a tracking unit for determining the respective current position of the instrument, in particular under the condition of using two-dimensional projection images of the X-ray device and / or a tracking system of the X-ray device. The tracking unit can provide this current position as initial position for the determination unit via the second interface, but also to other functional units of the control device. Additionally or alternatively, the control device can also have a path determination unit which can also obtain the initial position in particular via the second interface and the vessel model via the first interface in order to determine a path through the vessel structure from the initial position of the instrument to the target position and to provide this path via the third interface. As is known in principle, the control device can also have a recording unit which has a recording operation of the X-ray device, for example for recording individual two-dimensional projection images, in particular perspective images, and / or a projection image group for a three-dimensional image data set. For this purpose, the control device can also have a corresponding reconstruction unit for reconstructing a three-dimensional image data set from the projection image group.

[0064] However, it is particularly advantageous if the control device also has a monitoring unit for checking whether the current position of the tracked instrument on the path reaches a support point which indicates a change in the projection geometry of the optimized course, and a control unit for controlling the adjustment device by means of the set of adjustment parameters of the projection geometry to be reset upon reaching such a support point, in particular after a user confirmation. The monitoring unit can use the current position of the tracking unit provided via the second interface. The monitoring unit can also be configured to monitor whether there is a user-side deviation from the projection geometry along the optimized course, and, in the event of a deviation, to initiate a new determination based on the set deviating projection geometry in accordance with the optimization process.

[0065] Furthermore, the X-ray apparatus can also have an operating device and an output device. The operating device can comprise, for example, a foot pedal by means of which the recording of two-dimensional projection images, in particular perspective images, can be triggered. Such a foot pedal has proven to be useful in particular when minimally invasive surgery is performed on the examination object, in which the user guides an instrument in the examination object. The foot pedal can also be used to confirm the setting of a new projection geometry. In general, the projection images, in particular perspective images, recorded with the projection geometry of the optimized course can be output on the output device, for example a monitor. Here, it is conceivable that the pre-processing known in principle, for example the superimposition with three-dimensional pre-operative image data sets and / or vessel models, in particular additional annotations, highlighting or replacement of the detected instrument, etc., can be performed. It is particularly advantageous if the control device can comprise an output unit for pre-processing and outputting the projection images recorded with the projection geometry along the optimized course. The output unit can preferably be configured for highlighting the (remaining) path to the target position. Here, it is particularly advantageous if the upcoming change in the projection geometry along the path can also be displayed, for example by changing the color of the highlighting, markers along the path, etc.

[0066] The computer program according to the application can be directly loadable into the memory means of the control device of the X-ray apparatus and has program means which, when the computer program is executed on the control device, cause the control device to carry out the steps of the method according to the application. The computer program can be stored on an electronically readable data carrier according to the application, which therefore comprises control information stored thereon, which at least includes the computer program according to the application and is designed such that, when the data carrier is used in the control device of the X-ray apparatus, the control device is configured to carry out the method according to the application. The electronically readable data carrier can be a non-transitory data carrier, for example a CD-ROM. BRIEF DESCRIPTION OF DRAWINGS

[0067] Further advantages and details of the application emerge from the embodiments described below and according to the drawings.

[0068] In the attached diagram:

[0069] Figure 1 A flowchart illustrating an embodiment of the method according to the present invention is shown;

[0070] Figure 2 A sketch of a vascular structure with support points is shown as an example;

[0071] Figure 3 The preprocessed projection image is shown schematically.

[0072] Figure 4 A schematic diagram of an X-ray apparatus according to the present invention is shown; and

[0073] Figure 5 The functional structure of the control equipment for an X-ray device is shown. Detailed Implementation

[0074] Figure 1 A flowchart illustrating an embodiment of the method according to the invention is shown. This method is used for planning image monitoring during minimally invasive surgery using instruments, particularly catheters, on the vascular structure, particularly a segment of the vascular system, of a patient being examined, and for setting up an X-ray device to record two-dimensional projection images, particularly fluoroscopic images, for image monitoring. Here, the X-ray device has a C-arm as a carrier for a recording device consisting of an X-ray radiator and an X-ray detector. The C-arm can be rotated about two axes by means of an adjustment device to set different projection geometries, here referred to as angulation of the C-arm. Each angulation is characterized by two angulation angles. Other designs providing additional or different adjustment possibilities for the carrier by means of the adjustment device are also conceivable. The X-ray device also has a collimation device associated with the X-ray radiator and a scaling device associated with the X-ray detector. The collimation device and scaling device can also be set by means of the adjustment device.

[0075] The following steps are performed with the aid of a control device of an X-ray apparatus. Here, in step S1 basic input information is received via a first interface and a second interface. Via the first interface, here an external interface, a vessel model 1 is received, which can be, for example, a planning result. The vessel model 1 can be derived with the aid of at least one trained analysis function from a three-dimensional image data set recorded before the operation or at the beginning of the operation, for example by detecting a center line of a vessel structure, which can also describe the course of a vessel or a vessel segment in the vessel model 1. Here, the three-dimensional image data set can be recorded with different imaging apparatuses, for example as a magnetic resonance image data set and / or a computed tomography image data set. However, the three-dimensional image data set can also be recorded with the X-ray apparatus itself, for example by rotating a C-arm (C-arm CT) around the examination object. In addition, in the latter case a registration to the coordinate system of the X-ray apparatus has already been given for the vessel model 1, in other cases a 2D-3D registration or a 3D-3D registration can be carried out on the basis of the images in the case of a C-arm CT, so that the vessel model 1 is known in the coordinate system of the X-ray apparatus in an ideal manner.

[0076] In the vessel model 1 a target position of the instrument has also been marked. In the case of a minimally invasive operation on a patient, the target position can be, for example, a thrombus to be removed or a blood-supplying vessel for embolization therapy.

[0077] In addition, in step S1 an initial position of the instrument in the vessel structure is received via the second interface, wherein several possibilities exist. On the one hand, the current position of the instrument can already be tracked in step S2. For this purpose, two variants can be thought of in the X-ray apparatus, which can also be used complementarily. In one variant, the instrument can be tracked in real time in a two-dimensional projection image, for example a perspective image, in such a way that a two-dimensional representation of the instrument in the perspective image is registered with a three-dimensional representation of the vessel structure, i.e. the vessel model 1, or a two-dimensional representation of the instrument in the perspective image is registered with a three-dimensional representation of the vessel structure, i.e. the vessel model 1. Here, the fact that the instrument has to be moved within the vessel structure can be utilized. Here, respiratory and cardiac movements and possible deformations of the vessel due to the instrument itself can be taken into account accordingly. Thus, the three-dimensional position of the instrument, preferably the three-dimensional position of the tip of the instrument, for example the tip of a catheter, is thereby known. In another variant, a tracking system of the X-ray apparatus is used to track the three-dimensional position of the instrument. For example, an electromagnetic and / or optoacoustic variant can be used. That is, in this first possibility the current position of the instrument can be used as the initial position 2. That is, in this case the second interface is an internal interface.

[0078] But the initial position 2 can also be given in another way in advance, for example when the instrument has not yet been inserted into the examination object. Thus, for example, a planned initial point in the examination object which can be reached in a simple manner can be used as the initial position 2. Such an initial position can also be given on the user side in the planning phase, for example.

[0079] In step S3, using the blood vessel model 1 with the target position and the initial position 2, a path through the blood vessel structure from the initial position 2 to the target position is determined, for example by means of a pathfinding algorithm. This can be the shortest possible path. The path is provided via a third interface, in the present example an internal interface.

[0080] In this case, Figure 2 The blood vessel structure 3, here a vessel tree which is a section of the blood vessel system of a patient, is shown purely schematically. The blood vessel structure 3 comprises a plurality of blood vessels or vessel sections which are connected at bifurcation points 4, i.e. branches / nodes, and are represented by their center lines. Furthermore, the initial position 2 and the target position 5 are shown, the target position 5 here exemplarily being a blood supply vessel to a tumor which is to be the object of an embolization treatment. The path 6 from the initial position 2 to the target position 5 is shown in a thicker line.

[0081] In step S4, support points 7 are specified along the path 6 (cf. Figure 2 ), wherein the initial position 2 and the target position 5 are preferably also used as support points 7. As can be seen from Figure 2 , in any case support points 7 are selected at the bifurcation points 4. Further support points 7 can also be used, for example at regular intervals between the bifurcation points 4, as is exemplarily shown here only between the last bifurcation point 4 and the target position 5.

[0082] Then, again with reference to Figure 1In step S5, an optimization procedure is carried out to determine an optimized course 9 of the projection geometry along the support points 7, thereby determining an optimized course 9 of the path 6. Here, a specific, for example set, projection geometry can be assumed, or a completely free choice can also be made, in particular when planning takes place beforehand. Here, the objective function of the optimization procedure, which is carried out using the Viterbi algorithm, contains not only a first term relating to the as good as possible recognizability of the relevant features in the two-dimensional projection image of the projection geometry, but also at least one second term which favors as small a number of changes in the projection geometry along the path 6. The first and second terms can be weighted in order to emphasize the respective aspects, and can also be selected by the user if necessary. In the present specific example, the already mentioned angulation angle is used as an optimization parameter, wherein further or other adjustment parameters of the carrier, here the C-arm, can also be used. Furthermore, collimation parameters relating to collimation and zoom parameters relating to zoom are expediently also used, the optimization aspects of which can be contained in the first term, but can also be reflected by a third term. Finally, boundary conditions are also used, thereby forming a high-dimensional, non-convex optimization problem with boundary conditions. The optimization problem can be written down schematically, such that the sought solution L, i.e. the optimized course (described by the optimization parameters for each support point 7) is obtained as follows:

[0083] L = argmin (first term + second term) s.t. boundary conditions.

[0084] The objective function (first term + second term) can also contain a third term and the boundary conditions expressed as boundary condition terms.

[0085] Here, the first term is selected from the group of terms comprising:

[0086] - for support points 7 at and / or within a certain tolerance range around a bifurcation point 4 of the vessel structure 3, a term for minimizing the deviation of the projection direction of the projection geometry from the course direction of the vessel at the bifurcation point 4 according to the vessel model 1,

[0087] - in particular for support points 6 which are not at the bifurcation point 4 and / or lie outside the tolerance range, a term for minimizing the visual shortening of at least the vessel in which the support point 7 lies and / or of all vessels which are visible in the projection geometry from the support point 7 to the target position 5, in particular in a manner which is weighted less with increasing distance from the support point 7 in the vessel structure 3,

[0088] - a term which favors the visibility of the instrument in the center of the projection image recorded using the projection geometry,

[0089] - The term that maximizes the visible length of the blood vessel along the path 6 from support point 7 to target location 5.

[0090] - Items that minimize the dose load on the examined subject and / or at least one treatment personnel and / or operator, and

[0091] - Items that minimize the obstruction of other structures of the object being examined, particularly bones, to at least a portion of the vascular structure 3, and particularly to instruments and / or the path 6 from the support point 7 to the target location 5.

[0092] Here, it should also be noted that, in particular, the application of contrast agents should preferably be chosen in terms of visual shortening or visible length, so as to best display the overall remaining path 6 to the target position 5.

[0093] The second option can be selected proportionally to the number of changes in the projected geometry along path 6 caused by the movement of the carrier, i.e., the C-arm. Here, in this embodiment, the intensity of the change can be used to weight each change in the projected geometry. Here, the change in the projected geometry can be determined by the same optimized parameter at adjacent support points 7, where the difference in the angularized angle is not equal to zero.

[0094] Regarding the collimation parameters and / or scaling parameters, for example, selections can be made to remove as accurately as possible all features or image components that are not relevant to the guidance of the instrument, such as all features or image components other than the instrument (assuming it is at the corresponding support point 7), the target location 5, and the blood vessels between them.

[0095] Boundary conditions may, for example, involve the pre-given arrangement of the X-ray detector above the object being inspected, the required collision-free movement path between two projective geometries, the visibility of the path 6 to the target location 5 for each projective geometry, and / or at least one constraint given by the technical design of the X-ray equipment.

[0096] For example, in Figure 2 In this case, up to the bifurcation point region 8 where the blood vessel branches downwards, it is still possible to image all blood vessel orientations and bifurcation points 4 with sufficiently high quality using a specific fixed projection geometry. However, the projection geometry should be modified at the bifurcation point region 8 to also display the bifurcation point 4 there, where possible, so that the blood vessel extends at least approximately parallel to the image plane of the recorded two-dimensional projection image. This required modification of the projection geometry can be correspondingly included in the optimized orientation 9 as a result of the optimization process in step S5 (see [link to optimization process]). Figure 1). For each of the projection geometries to be used, corresponding adjustment information for adjusting the device is also provided in step S5 in order to be able to control it directly.

[0097] In the present example, a global optimum can be found due to the use of the Viterbi algorithm, wherein, however, discrete values are used for the optimization parameters, for example angles with an interval of 1° to 10°. Other solution methods can also be used.

[0098] Then, in a further procedure or while performing the operation, the first projection geometry is automatically set in step S6 if necessary. Then, in step S7, a two-dimensional projection image, for example a perspective image, can be recorded in this projection geometry, if necessary in accordance with a user's request, by means of the foot pedal of the X-ray device. Here, according to step S8, it is continuously checked using the current position of the instrument provided by the tracking step S2 whether a support point 7 has been reached at which the optimized course 9 indicates a projection geometry change. If this is the case, the user is advised to reset the projection geometry, which the user can then likewise adopt using the already mentioned foot pedal or other operating means and thus release the automatic setting in step S9 in accordance with the corresponding adjustment information. It is particularly preferred that the automatic setting of the new projection geometry and the recording of further two-dimensional projection images, that is to say in particular perspective images, can be released by means of the foot pedal.

[0099] However, since the user can also deviate from the suggested projection geometry purposefully, this can be checked in step S10. Upon deviation, a new optimization procedure is initiated in step S5, wherein the initial position 2 is now the current position of the instrument and the projection geometry set on the user side is assumed.

[0100] If it is determined in step S8 that the projection geometry does not need to be changed or if it is determined in step S10 that there is no change in the projection geometry on the user side, it is returned to step S7, whereby the two-dimensional projection image is recorded, if necessary in accordance with the corresponding request.

[0101] In a step not shown for the sake of clarity, the projection image recorded in step S7 is caused to be displayed on an output device, for example a monitor of the X-ray device. Here, the two-dimensional projection image can also be preprocessed, for example by highlighting the instrument and / or the (remaining) path 6. In this preprocessing, the user can also already be indicated of the impending change in the projection geometry along the path 6.

[0102] Figure 3An exemplary pre-processed projection image 10 is shown. It can be seen that the instrument 11, more precisely the instrument tip, is highlighted, wherein the instrument 11 is located exactly at a bifurcation point 4, which is suitably seen due to the optimized course 9 of the projection geometry, such that the corresponding blood vessel deviates at least only slightly from the parallel to the image plane in its course. The further path 6 up to the target position 5 is also shown in a highlighted manner. The symbol 12 indicates that the projection geometry is to be changed in the region of the bifurcation point 8. It can also be seen that a tumor 13 to be treated in the present example.

[0103] Here, the instrument 11 is arranged in a position as central as possible, as desired by many users and facilitated by corresponding first items and / or suitable boundary conditions.

[0104] When the target position 5 is reached, the method ends.

[0105] Figure 4 A schematic sketch of an X-ray device 14 according to the application is shown. The X-ray device 14 has a C-arm 15 as a carrier, which is held on a stand 16 and can be angularized in different ways by means of an adjusting device 17, as is schematically shown by the arrow 18. An X-ray emitter 19 with a collimator 20, which can also be adjusted by means of the adjusting device 17, and an X-ray detector 21 are arranged oppositely on the C-arm 15. An examination object 22, here a patient 23, can be placed on a patient table 24.

[0106] Here, in addition to a control device 25 for controlling the operation of the X-ray device 14, the X-ray device 14 comprises a collision protection system 26 for avoiding collisions of components of the X-ray device 14 with other components, persons and / or further objects, as is known in principle from the prior art. The collision protection system 26 can provide information, for example, as to whether a change between projection geometries can be made without a collision occurring. Furthermore, a tracking system 27 for the instrument 11, which is only indicated here, is provided, which serves for the position determination of the instrument 11, which can work, for example, in an electromagnetic or opto-acoustic manner.

[0107] A display 28 as an output device 29 can be used to display projection images 10, in particular perspective images, which have been pre-processed in a manner that is clearly visible from the surgical position on the patient 23. Simple user inputs can be made by means of a foot pedal 30 as an operating device 31, for example in order to release the radiation for recording the projection images and / or in order to confirm the suggested projection geometry.

[0108] Of course, the X-ray device 14 can also have other components, for example a sensor mechanism for dose monitoring and other operating means and / or output means.

[0109] Figure 5 The functional structure of the control device 25 is shown in more detail with respect to some functional units. In addition to the storage means 32, the control device 25 first of all comprises a first interface 33, which is an external interface here. The blood vessel model 1 can be accepted via this first interface in the course of step S1. The tracking unit 34 provides the current position of the instrument 11, in particular of the instrument tip of the instrument 11, via a second interface 35, which is an internal interface here, in particular again in the course of step S1, using the two-dimensional projection images recorded according to step S2 and / or the tracking system 27.

[0110] The path determination unit 36 determines a path 6 from the initial position 2 to the target position 5 according to step S3 using the current position as the initial position 2 and using the blood vessel model 1 with the target position 5. This path 6 is provided via a third interface 44, which is again an internal interface here. The support points 7 are then specified in a specification unit 37 according to step S4. An optimization process can then be carried out in a determination unit 38 according to step S5, in particular together with the determination of the corresponding adjustment information.

[0111] The control unit 39 uses the adjustment information to set the projection geometry of the optimized course 9 according to steps S6 and S9. As is known in principle, the projection images can be recorded with the aid of a recording unit 40, in particular also in step S7. In the case of three-dimensional recording (C-arm CT), a reconstruction unit 41 can be used to reconstruct a three-dimensional image data set from the projection images.

[0112] If the instrument 11 is at different current positions along the path 6, which are provided by the tracking unit 34, the monitoring unit 42 can monitor according to step S8 whether the projection geometry is to be changed according to the optimized course 9 and trigger corresponding measures. The monitoring unit 42 can also monitor according to step S10 whether the user deviates from the projection geometry of the course 9.

[0113] Finally, the control device 25 can also have an output unit 43, in which the pre-processed projection images 10 can be determined, in particular in order to additionally mark the positions at which the projection geometry is changed.

[0114] The control device 25 can of course also have further functional units, which are not shown in detail here for reasons of clarity, for example a user interaction unit with respect to the foot pedal 30 or the other operating means 31, a dose monitoring unit for providing information about the corresponding first term of the target function, etc.

[0115] In this patent application, persons of either male or female gender identity shall be included regardless of the grammatical gender of the particular term.

Claims

1. Computer-implemented method for operating an X-ray apparatus (14), the X-ray apparatus (14) having a carrier and a regulating device (17) for moving the carrier, in particular a C-arm (15), in order to set a projection geometry, an X-ray emitter (19) and an X-ray detector (21) being arranged opposite one another on the carrier, the method comprising the following steps: - providing a vessel model (1) of a vessel structure (3) of an examination object (22), the vessel model (1) in particular describing a vessel course in three dimensions by means of center lines, a projection image of the examination object (22) being recordable with the X-ray apparatus (14), wherein a target position (5) of an instrument (11) movable in the vessel structure (3) is marked in the vessel model (1), - providing an initial position (2) of the instrument (11) in the vessel structure (3) of the vessel model (1), - providing a path (6) in the vessel structure (3) of the vessel model (1) from the initial position (2) of the instrument (11) to the target position (5), - specifying support points (7) along the path (6), - determining an optimized course (9) of the projection geometry for the support points (7) in an optimization process of an objective function in the case of use of the vessel model (1), wherein the objective function comprises, in addition to at least one first term, at least one second term, the at least one first term relating to an optimization of an image content for an observer at the respective support point (7), the at least one second term minimizing a number of changes of the projection geometry along the path (6) by means of the movement of the carrier, and - determining, for each projection geometry, a regulating parameter for controlling the regulating device (17). The vessel model (1) to be provided is determined from a three-dimensional image data set of the examination object (22), which is registered to a coordinate system of the X-ray apparatus (14), or is registered to a coordinate system of the X-ray apparatus (14). The initial position (2) is determined from at least one two-dimensional projection image, in particular a perspective image, of a current projection geometry, in particular under the condition of additional use of the vessel model (1) and / or the three-dimensional image data set, and / or under the condition of use of a tracking system (27) of the X-ray apparatus (14). The support points (7) are specified at least at nodes of the vessel structure (3), in particular bifurcation points (4), of a plurality of vessel junctions, and / or the support points (7) are selected at least partially along at least one center line of a vessel of the path (6) at certain intervals. At least one of the at least one first term is selected from the group comprising: - a term relating to an optimization of an image content for an observer at the respective support point (7), ​ ​ 2. The method of claim 1, wherein, ​ 3. The method according to claim 1 or 2, characterized in that, ​ 4. The method according to any of the preceding claims, characterized in that, ​ 5. The method according to any of the preceding claims, characterized in that, ​ - for support points (7) at and / or within a tolerance range around a bifurcation point (4) of the vascular structure (3), a term for minimizing the deviation of the projection direction of the projection geometry from the direction of the vascular structure at the bifurcation point (4) according to the vascular model (1), - in particular for support points (7) not at the bifurcation point (4) and / or lying outside the tolerance range, a term for minimizing the apparent shortening of at least the vessel in which the support point (7) lies and / or of all vessels visible in the projection geometry along the path (6) from the support point (7) to the target position (5), in particular in a manner that weighs less as the distance from the support point (7) in the vascular structure (3) increases, - a term for facilitating the visibility of the respective support point (7) in the center of the projection image recorded with the projection geometry, - a term for maximizing the visible length of the vessel along the path (6) from the support point (7) to the target position (5), - a term for minimizing the dose load of the examination object and / or at least one treatment person and / or operating person, and - a term for minimizing the occlusion of at least a portion of the vascular structure (3), in particular of the respective support point (7) and / or the path (6) from the support point (7) to the target position (5), by other structures of the examination object (22), in particular by bone.

6. The method according to any of the preceding claims, characterized in that, The second term is selected in proportion to the number of changes of the projection geometry along the path (6) and / or each change of the projection geometry is weighted with a strength of the change.

7. The method according to any of the preceding claims, characterized in that, For the second term, the changes of the projection geometry are determined from one support point (7) to the next support point (7) in dependence on changes of at least one adjustment parameter of the carrier, in particular of the angulation angle thereof.

8. The method according to any of the preceding claims, characterized in that, For each projection geometry, at least one collimation parameter is also determined, which describes the collimation of the projection image to be recorded, and / or a scaling parameter, which describes the scaling of the projection image to be recorded.

9. The method according to any of the preceding claims, characterized in that, At least one boundary condition is used as a boundary condition term of the target function and / or as a term to be checked additionally.

10. The method according to any of the preceding claims, characterized in that, When a projection geometry deviating from the optimized course (9) is set on the user side, a new determination is made according to the optimization process on the basis of the set deviating projection geometry.

11. An X-ray apparatus (14) having a carrier, an adjustment apparatus (17) and a control apparatus (25), on which a X-ray emitter (19) and a X-ray detector (21) are arranged opposite to each other, the adjustment apparatus (17) being at least for moving the carrier in order to set a projection geometry, wherein, The control device (25) has: - a first interface (33) for providing a vascular model (1) of a vascular structure (3) of an examination object (22), which vascular model (1) describes the vascular course in three dimensions, in particular by means of center lines, with which a projection image of the examination object (22) can be recorded with the X-ray device (14), wherein a target position (5) of an instrument (11) movable in the vascular structure (3) is marked in the vascular model (1), - a second interface (35) for providing an initial position (2) of the instrument (11) in the vascular structure (3) of the vascular model (1), - a third interface (37) for providing a desired position (5) of the instrument (11) in the vascular structure (3) of the vascular model (1), - a third interface (44) for providing a path (6) in the vessel structure (3) of the vessel model (1) from an initial position (2) of the instrument (11) to the target position (5), - a specification unit (37) for specifying support points (7) along the path (6), and - a determination unit (38) for determining an optimized course (9) of the projection geometry for the support points (7) in an optimization process of an objective function under the condition of using the vessel model (1), wherein the objective function comprises, in addition to at least one first term, at least one second term, the at least one first term relating to an optimization of the image content for the observer for the instrument (11) located at the respective support point (7), the at least one second term minimizing the number of changes of the projection geometry along the path (6) by the movement of the carrier, and the determination unit (38) is for determining, for each projection geometry, an adjustment parameter for controlling the adjustment device (17).

12. Computer program having program means which, when the computer program is executed on a control device (25) of an X-ray device (14), cause the X-ray device (14) to perform the method according to any one of claims 1 to 10.

13. Electronically readable data carrier on which the computer program according to claim 12 is stored.

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