Medical instrument with positioning X-ray markers and computer-implemented method for determining positioning information and X-ray device

Abstract

The invention relates to a medical instrument (10, 20, 25, 41) for invasive use, comprising an X-ray marker arrangement with at least two X-ray marker regions (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46), characterized in that the X-ray marker regions (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) are designed in such a way that they each have different absorption properties for X-radiation with different energy spectra, that the X-ray marker regions (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) are arranged successively on the instrument (10, 20, 25, 41) are arranged, and that the X-ray marker areas (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) each have a different metal content.Furthermore, the invention relates to a computer-implemented method for determining positioning information for such a medical instrument (10, 20, 25, 41).

Description

[0001] The invention relates to an instrument for invasive medical use with positioning X-ray markers and a computer-implemented method for determining positioning information. The invention also relates to an X-ray device configured to carry out the method, as well as a corresponding computer program product and computer-readable storage medium.

[0002] The determination of positioning information for invasive instruments using X-ray markings is known in the prior art, e.g. from the documents US 2012 / 0 283 545 A1, US 2013 / 0 345 550 A1, US 5 409 004 A, or US 2007 / 0 265 516 A1.

[0003] Instruments for invasive medical use can include guidewires, catheters, endoscopes, laparoscopes, surgical tools, or needles. Needles can be, for example, biopsy needles or ablation needles. Ablation needles, such as microwave (MW) or radiofrequency (RF) needles, are used, among other things, for the thermal ablation of tumors. For liver tumors, for example, MW / RF needles are inserted into the human body and into the liver until they reach the tumor. Biopsy needles are inserted into soft tissue or bone anywhere in the body until they reach a tumor or lesion.

[0004] Image guidance based on CT images is often used for invasive needle insertion. CT images make it possible to determine how far the needle has been inserted into the body and where it is positioned within the body. Image guidance based on CT images is usually based on the step-and-shoot method. The needle is advanced step by step under CT monitoring, and the progression and position of the needle are checked between each step. The CT images available for monitoring are usually thin tomograms, also known as slices. The thin tomograms may include one or more slices.

[0005] A practical problem with thin tomographic images arises when using so-called "double oblique" needle trajectories, which are advantageous for the patient at a variety of target locations. Double oblique needle trajectories generally do not run within a tomographic image, but rather are inclined at a certain angle to the plane of the tomographic image. In such cases, thin tomographic images only show the small longitudinal section of the needle that traverses the spatial area depicted in the tomographic image. Additional longitudinal sections of the needle lie outside the tomographic image on either side. This complicates orientation during CT needle guidance, as it is not possible to determine which longitudinal section of the needle is depicted in the tomographic image or how far the needle has already been inserted into the body.

[0006] Laser guidance is often available on interventional CT scanners, which supports manual guidance of the needle along a planned needle trajectory, which can be particularly helpful for double-oblique trajectories. However, as soon as the needle deviates from the planned trajectory, for example, due to deformation of the punctured tissue or patient movement, the step-and-shoot technique must be reverted to.

[0007] Another practical problem with thin slice images arises in multi-needle procedures (e.g., multi-needle MW ablations or multi-needle cryoablations). In multi-needle procedures on larger tumors, precise positioning of all needles is important to ensure complete and precise ablation of the tumor. However, in multi-needle procedures, it is often difficult to distinguish between the needles in the CT image, which complicates orientation and slows down such procedures.

[0008] It is also known to use optical or electromagnetic navigation systems to navigate the needle. However, the equipment required for this is expensive. Optical navigation, in particular, can only detect the proximal, externally located longitudinal section of the needle, but not the distal longitudinal section. Electromagnetic tracking elements integrated into the needle tip are known for detecting the distal longitudinal section of the needle. However, these have the disadvantage of requiring additional electrical cables and electromagnetic field generators, which can complicate handling and require additional space.

[0009] The object of the invention is to support invasive procedures with one or more instruments by determining and outputting positioning information regarding the current position of the respective instrument without the need for additional positioning or tracking systems.

[0010] The invention solves this problem by a medical instrument, a method, an X-ray device as well as a computer program product and a computer-readable storage medium according to the independent claims.

[0011] The invention requires the use of spectral X-ray imaging. Spectral X-ray imaging, such as dual-energy CT (DECT), exploits the fact that materials exhibit different absorption properties at different X-ray energies. Furthermore, the absorption properties for the respective X-ray energies can differ from material to material. In spectral imaging, two different X-ray energy levels are used to generate images. Materials such as bone, soft tissue, or contrast agents absorb X-rays to varying degrees depending on the X-ray energy level. By analyzing X-ray absorption at different X-ray energy levels, specific information about the composition of materials or the presence of certain materials can be obtained. For example, calcium in vessels can be distinguished from iodine-based contrast agents.

[0012] Examples of spectral X-ray imaging include CT scanners with photon-counting detectors, dual-source dual-energy CT scanners, and dual-energy CT scanners with dual-layer detectors. Other examples of spectral X-ray imaging include C-arm X-ray machines with two X-ray sources with different X-ray energy levels, as well as C-arm X-ray machines with a single X-ray source that can be switched between different X-ray energy levels or that can be switched between different X-ray filters.

[0013] The invention further requires an instrument having regions with different spectral X-ray absorption characteristics, i.e. regions which each have different absorption properties for X-rays with different energy spectra.

[0014] According to the invention, spectral X-ray imaging captures images of a slice or volume, with at least a portion of the instrument located within the slice or volume. Tracking the instrument position can then be achieved by spectral position coding along the instrument. Spectral position coding means that the spectral X-ray absorption characteristic of the portion of the instrument located in the image can be used to determine which portion of the instrument is being examined. This advantageously exploits the fact that spectral X-ray images allow for good differentiation between materials with different spectral X-ray absorption characteristics, which is not possible in a comparable manner with non-spectral X-ray images.

[0015] If the spectral X-ray absorption characteristics of the instrument sections are known in advance, for example, from manufacturer's specifications regarding the instrument or from a previously acquired spectral calibration X-ray image, the overall position of the instrument is also known with the knowledge of the instrument section. If the spectral X-ray absorption characteristics of the instrument sections are not known in advance, it is nevertheless possible to track whether and how often successive sections of the instrument have passed through the image section. If the successive sections have a known length, for example, the distance the needle has been advanced can be determined from counting the section changes in the image section.If a specific sequence of spectral X-ray absorption characteristics of the instrument sections is known in advance, the sequence in the image section can be used to infer when a predetermined needle advance has been reached. For example, the spectral X-ray absorption characteristics could be constant over a certain length of the needle and only change in a final longitudinal section; then, from this change, it could be used to infer when the final section has been reached. For example, the spectral X-ray absorption characteristics could change monotonically over a certain length of the needle and only change non-monotonic, i.e., in the opposite direction, in a final section of its life; then, from this opposite change, it could be used to infer when the final section has been reached.

[0016] A medical instrument according to the invention for invasive use comprises an X-ray marker arrangement with at least two X-ray marker regions. The X-ray marker regions are configured such that they each have different absorption properties for X-ray radiation with different energy spectra. The X-ray marker regions are arranged consecutively on the instrument with respect to a predetermined spatial direction.

[0017] The invention makes it possible to determine information regarding the positioning of an invasive instrument relative to a tomographic image based on the different absorption properties of the X-ray marker regions, without the instrument having to be completely imaged in the tomographic image and without requiring a separate tracking system. Providing an instrument according to the invention with spectral X-ray marker regions, e.g., in the form of coatings or a variation in the material composition of the instrument itself, is inexpensive. Furthermore, the instrument retains its basic design, and therefore its handling advantageously remains unchanged.

[0018] According to an advantageous embodiment of the invention, the instrument is elongated, and the predetermined spatial direction corresponds to the longitudinal direction of the instrument. This makes it possible to identify the respective longitudinal section of the instrument based on the different absorption properties of the X-ray marker areas.

[0019] According to the invention, the X-ray marker regions each have a different metal content. Metal content can be understood as a varying amount of metal as well as a varying mixing ratio of metal with other metals or materials in an alloy. With a varying mixing ratio, the amount of metal does not necessarily have to vary. The only important thing is that the different metal content results in different spectral absorption properties. Varying the metal content represents a particularly simple and inexpensive way to vary the spectral absorption properties. Furthermore, metal is a material typically frequently used in invasive medical instruments.

[0020] According to one embodiment of the invention, the X-ray marker regions are configured as spatially separated X-ray markers. This spatial separation enables particularly good and easy detection of the respective X-ray marker region in X-ray images, since the spatial separation represents a reliably recognizable feature in images.

[0021] According to one embodiment of the invention, the X-ray marker regions are formed as regions of a one-piece X-ray marker. A one-piece design avoids separation regions that, depending on the design of the X-ray marker regions, could cause surface irregularities at the region boundaries or discontinuous changes in the properties and condition of the surface or instrument at the region boundaries.

[0022] According to one embodiment of the invention, the differences in the absorption properties of the X-ray marker regions for X-ray radiation with different energy spectra change gradually from one X-ray marker region to another. A gradual or stepwise change can be detected particularly reliably in spectral X-ray images. The individual steps represent particularly reliably recognizable information about the X-ray marker region located in the X-ray image, since the steps can be reliably assigned to a position in the X-ray image.

[0023] According to one embodiment of the invention, in addition to the X-ray marker arrangement, at least one further X-ray marking is provided on the instrument. This marking is designed to have different absorption properties for X-rays with different energy spectra, and is arranged to spatially encompass the X-ray marker arrangement. The further X-ray markings can be designed specifically for the instrument. The X-ray markings then advantageously make it easy and reliable to identify which instrument is visible in the X-ray image, or to easily and reliably distinguish between the instruments each provided with specific X-ray markings.

[0024] Further embodiments and advantages emerge from the dependent patent claims and from the following description of embodiments with reference to figures.

[0025] The figures show: Fig. 1 needle with section-wise spectral X-ray absorption characteristics Fig. 2 needles with additional spectral X-ray marking Fig. 3 X-ray equipment Fig. 4 Layer image with needle section and positioning information Fig. 5 Methods for carrying out the invention Fig. 6 Method for carrying out an advantageous embodiment

[0026] In Fig. Figure 1 schematically illustrates a needle 10 as an example of a medical instrument for invasive use. The needle 10 has a needle tip 12 at its distal end. The needle 10 generally has a conventional shape. The needle 10 may, for example, be a standard MW / RF ablation needle.

[0027] According to one embodiment of the invention, the needle 10 comprises a metal or other material mixture or composition that spatially varies along the length of the needle 10. A key factor in the selection of the material is that it exhibits spectral X-ray absorption properties that can be determined using the X-ray parameters commonly used in medical imaging. In addition to metal, numerous other materials such as iodine, calcium, barium, gold, or lead can be used for this purpose.

[0028] The varying material compositions can, for example, be applied as a coating to the body of the needle 10. For example, the needle 10 could also be coated with metal or another material with a varying layer thickness. Alternatively, the material from which the body of the needle 10 is formed could also vary. Instead of a needle 10, for example, it could also be a bone trocar consisting of an outer metal tube and an inner hard metal pin. The metal tube and / or hard metal pin could have a metal or other material composition that varies spatially along the length of the trocar.

[0029] Due to the differences in the respective metal or material composition or coating, spatially varying amounts of the respective metals or materials result along the length of the needle 10, and thus spatially varying spectral X-ray absorption properties. The spatially varying spectral X-ray absorption properties form an X-ray marker arrangement of successive X-ray marker regions 13, 14, 15, 16, 17 along the length of the needle 10, each of which has different X-ray absorption properties for X-ray radiation with different energy spectra. The spectral X-ray absorption properties can, for example, be changed stepwise from X-ray marker region 13, 14, 15, 16, 17 to X-ray marker region 13, 14, 15, 16, 17. Alternatively, the spectral X-ray absorption properties could be continuously modulated along the length, rather than changing stepwise from region to region.

[0030] For example, the "spectral absorption ratio" of X-ray marker regions 13, 14, 15, 16, and 17, defined by dividing the absorption coefficient of hard X-rays (X-ray energy >120 keV) by the absorption coefficient of soft X-rays (X-ray energy <70 kEV), could be 20% higher in X-ray marker region 13 than in X-ray marker region 14. These spectral X-ray absorption properties can be achieved, for example, by varying metal mixtures of elements such as iron, tantalum, bismuth, copper, and others. Alternatively or additionally, they can also be achieved, for example, by using non-metallic elements such as carbon, hydrogen, or oxygen as components of the material mixtures.

[0031] In Fig. 2 schematically illustrates two needles 20, 25 as invasive instruments, as an example of a further embodiment of the invention. The needles 20, 25 each have an X-ray marker arrangement of consecutive X-ray marker regions 22, 23, 24, 27, 28, 29 along the length of the respective needle 20, 25. The X-ray marker regions 22, 23, 24, 27, 28, 29 have different spectral X-ray absorption properties. In this regard, reference is made to the preceding description of the figures.

[0032] In addition, the needles 20, 25 each have an X-ray marking 21, 26. The X-ray markings 21, 26 are located in close proximity to the respective X-ray marker areas 22, 23, 24, 27, 28. The purpose of this close proximity is that, in an X-ray tomographic image or an X-ray volume image, whenever an X-ray marker area 22, 23, 24, 27, 28 is included in the image, the respective X-ray marking 21, 26 is also included in the image.

[0033] The X-ray markings 21, 26 can, for example, be applied as a background coating to the respective longitudinal section of the respective needle 20, 25 and be formed by a layer located beneath the respective X-ray marker regions 22, 23, 24, 27, 28. Conversely, the X-ray markings 21, 26 can, for example, also be formed by a layer located above the respective X-ray marker regions 22, 23, 24, 27, 28. The X-ray markings 21, 26 can, for example, also be formed by a layer arranged around the respective X-ray marker regions 22, 23, 24, 27, 28.

[0034] The X-ray markers 21, 26 exhibit different spectral X-ray absorption properties. This allows for differentiation between the X-ray markers 21, 26 and thus between the needles 20, 25. This allows for the determination of which of the two needles 20, 25 is depicted in each image using spectral X-ray images. This is particularly advantageous for multi-needle procedures. In a procedure involving multiple needles 20, 25, needle 20 has an X-ray marker 21 with different spectral X-ray absorption properties than the X-ray marker 26 of needle 25. This enables spectral identification of the needles 20, 25 and thus their differentiation. The spectral X-ray absorption properties of the X-ray marker regions 22, 23, 24, 27, 28 can also be analyzed simultaneously.

[0035] In Fig. 3 schematically illustrates an X-ray device 31. The X-ray device 31 comprises a C-arm 38 with an X-ray source and an X-ray detector. The C-arm 38 is configured in a generally known manner to generate spectral X-ray image data sets. For this purpose, the C-arm 38 is capable of acquiring X-ray images at different X-ray energy levels. This could be achieved in a known manner, for example, by switching the X-ray energy of the X-ray source. Alternatively, the arrangement could comprise two X-ray sources operated at different X-ray energy levels. The only essential requirement is that spectral X-ray image data sets can be generated.

[0036] The X-ray device 31 is also configured in a known manner to generate CT image data sets. For this purpose, the C-arm 38 is capable of recording a plurality of 2D projections from different projection angles by moving it around an examination object, for example, a patient, on a circular trajectory. CT image data sets, i.e., 3D images, are reconstructed from the 2D projections. The 3D images can be generated by the X-ray device 31 in a known manner as spectral X-ray image data sets.

[0037] The X-ray device 31 includes a control device 34 that controls the movement of the C-arm 38 and enables the operation of the X-ray device 31. The control device 34 includes a computer unit 32 configured for image processing and 3D reconstruction. The computer unit 32 is capable of generating both 2D X-ray images and 3D image data sets, both non-spectral and spectral.

[0038] The X-ray device 31 further comprises a screen 33 on which images generated by the control device 34 can be displayed.

[0039] Optionally, the control device 34 can receive image data from an ultrasound device 36. The ultrasound device 36 comprises an ultrasound head 35 for generating ultrasound images of an examination subject. The ultrasound images can be 2D images or 3D images in a known manner. The computer unit 32 is capable of combining image data from the ultrasound device 36 with image data from the X-ray device 31 in a known manner, for example, by fusion or mutual superimposition.

[0040] Optionally, the control device 34 can receive data from a data source 37. The data source 37 can be an integral part of the control device 34, integrated into the X-ray device 31. However, the data source 37 can also be provided separately from the control device 34 and connected to it only via a data connection. The data connection can be wireless or wired. The data source 37 can, among other things, provide specific information regarding invasive medical instruments. The specific information can, for example, originate from the manufacturer of the invasive instruments or be obtained from a caliber X-ray image.

[0041] In Fig. Figure 4 schematically shows a tomographic image 40 of a specimen under examination. The tomographic image 40 is a 3D image reconstructed by the X-ray device 34, representing a slice of the specimen under examination. Alternatively, the tomographic image 40 could also have been generated by the ultrasound device 36.

[0042] A structure 48 is schematically sketched in the tomographic image 40. Structure 48 could, for example, be an anatomical organ or a lesion or region with tissue changes.

[0043] Furthermore, an invasive medical instrument, namely a needle 41, is schematically depicted. The needle 41 does not run within the image plane of the tomographic image 40, but at an oblique angle to it. It thus crosses the tomographic image 40. Therefore, the needle 41 is not depicted in its entirety in the tomographic image 40, but only a short longitudinal section of the needle 41. This is indicated by two dashed lines 48, 49. Only the longitudinal section of the needle 41 lying between the dashed lines 48, 49 is included in the tomographic image 40. The sections outside the dashed lines 48, 49 are not included in the tomographic image 40 and are in Fig. 2 is shown only for better understanding.

[0044] According to the invention, spectral X-ray absorption characteristics of the longitudinal section of the needle 41 encompassed in the tomographic image 40 are determined, i.e., the different X-ray absorption of this longitudinal section for X-rays of different X-ray energy levels is determined. To determine spectral X-ray absorption characteristics, X-ray images are acquired by the X-ray device 34 using different X-ray energy levels. If the tomographic image 40 was generated from the outset as a spectral tomographic image 40, the spectral X-ray absorption characteristics can be derived directly from the tomographic image 40.

[0045] Alternatively, the tomographic image 40 could be received, for example, by the ultrasound device 36. In this case, the spectral X-ray absorption characteristics of the longitudinal section of the needle 41 could be specifically determined by the X-ray device 34. The tomographic image 40 could then be registered with the coordinate system of the X-ray device 34. In this way, the spectral X-ray absorption characteristics of the longitudinal section of the needle 41 depicted in the tomographic image 40 could be spatially correctly assigned by means of the registration.

[0046] The needle 41 has a plurality of X-ray marker regions 42, 43, 44, 45, 46. The X-ray marker regions 42, 43, 44, 45, 46 exhibit different X-ray absorption characteristics. According to the invention, positioning information regarding the needle 41 can be determined based on the spectral X-ray absorption characteristics determined by the X-ray device 34 for the longitudinal section of the needle 41 shown in the tomographic image 40. For example, a data source 37 could include an assignment of the specific spectral X-ray absorption characteristic to the respective X-ray marker area 42, 43, 44, 45, 46 as well as an assignment of the respective X-ray marker area 42, 43, 44, 45, 46 to its arrangement on the needle 41. For example, the data source 37 could store for each X-ray marker area 42, 43, 44, 45, 46 how far a respective X-ray marker area 42, 43, 44, 45, 46 is from the tip of the needle 41.In other words, based on the determined X-ray absorption characteristic and the information obtained from the data source 37, it could be determined which of the X-ray marker areas 42, 43, 44, 45, 46 is contained in the tomographic image 40 and on which longitudinal section of the needle 41 it is arranged.

[0047] Specifically, Fig. 4, it can therefore be determined based on the X-ray absorption characteristic that the X-ray marker region 44 is represented in the tomographic image 40. From the information regarding its arrangement on the needle 41, it would therefore be specifically determined, for example, how far the X-ray marker region 44 is from the tip of the needle 41. From this, it would be specifically derived, for example, how far the needle 41 has been advanced beyond the region of the examination object represented in the tomographic image 40 or how far the tip of the needle 41 is from the region of the examination object represented in the tomographic image 40.

[0048] In Fig. 5 a method for carrying out the invention is explained.

[0049] In step S1, the computer unit 32 receives a tomographic image 40. The tomographic image may be a spectral CT image. Alternatively, it could also be an ultrasound image.

[0050] In step S2, an invasive medical instrument or needle 41 is detected in the tomographic image 40. The instrument or needle 41 can be detected using a known image processing method, e.g., a pattern recognition method.

[0051] In step S3, a spatial position of the instrument or needle 41 in the image is detected.

[0052] In step S4, a spectral X-ray image data set is generated which at least includes the previously detected spatial position.

[0053] In step S5, a spectral parameter value for the spatial position of the instrument or needle 41 is determined based on the spectral X-ray image data set. In order to use the position from the tomographic image 40, the tomographic image 40 must be registered with the X-ray device 31 that generated the spectral X-ray image data set. If the tomographic image 40 was generated by the X-ray device 31 itself, it is registered with it from the outset. If the tomographic image 40 originates from another image source, registration must first occur. Registration can occur in a known manner. Registration can occur, for example, based on the image data itself by registering the tomographic image 40 of the examination object and the instrument or needle 41 with image data of the examination object and the instrument or needle 41 from the X-ray device 31, for example using a known image registration method.Known methods, for example, register image data using landmarks recognizable in the image data. Landmarks can be, for example, instruments, needles, or anatomical features of the object under examination. Known methods can also register image data by maximizing the similarity between the image data to be registered.

[0054] In step S6, positioning information associated with the parameter value is determined. The positioning information comprises direct or indirect information regarding the positioning of the instrument or needle 41 depicted in the tomographic image 40 relative to the region of the examination object depicted by the tomographic image 40. The determination of positioning information associated with the parameter value can, for example, be based on the fact that the spectral X-ray absorption properties of regions of the instrument or needle 41, as well as of X-ray marker regions 42, 43, 44, 45, 46 thereof, are previously known. They can either be known in advance as characteristic values ​​of the instrument or needle 41. Or they can have been previously determined and stored based on a preceding calibration measurement, for example, using the X-ray device 31 itself.The spectral X-ray absorption properties could change gradually or incrementally from region to region. The spectral X-ray absorption properties could also change continuously across regions. The spectral X-ray absorption properties could also change continuously within regions and gradually or incrementally between regions.

[0055] In step S8, the positioning information or information derived therefrom is output via an output device 33. The output via the output device 33 allows a viewer to see how far the instrument or needle 41 has been pushed through the area of ​​the examination object shown in the tomographic image 40 or how far the tip of the instrument or needle 41 is from the shown area.

[0056] The Fig. To summarize the method explained in Figure 5, if the slice image 40 is a slice or a thin volume of a spectral CT image dataset, the part of the instrument or needle 41 that intersects the image is located by image analysis using a standard instrument or needle detection algorithm known from the prior art. Which X-ray marker region 42, 43, 44, 45, 46 is imaged is then determined based on the observed spectral absorption ratio. Furthermore, the angle of inclination of the instrument or needle 41 relative to the slice image 40 can be determined by image analysis. By combining the information about the position of the X-ray marker region(s) 42, 43, 44, 45, 46, whichwhich intersect the tomographic image 40, with the detected position and inclination of the instrument or needle 41, the complete 3D pose and 3D position of the instrument or needle 41 with respect to the tomographic image 40 can be calculated.

[0057] Alternatively, if the tomographic image 40 is an ultrasound image, the information about which X-ray marker region 42, 43, 44, 45, 46 of the instrument or needle 41 intersects the ultrasound image plane can be determined based on the spectral absorption ratio. For this purpose, the tomographic image 40 is registered with the coordinate system of the X-ray device 31, or the coordinate system of the ultrasound device 36 is registered with the coordinate system of the X-ray device 31. Based on the registration of the coordinate system, the position of the instrument or needle 41 in the tomographic image 40 can be spatially assigned to a position in the coordinate system of the X-ray device 31. Based on the thus assigned spatial position, a spectral X-ray image of the instrument or needle 41 can then be taken using the X-ray device 31.A locally limited spectral X-ray image of the position in question is sufficient, and does not necessarily require a full CT reconstruction. For a locally limited spectral X-ray image, a small number of at least two X-ray projections from different projection angles is sufficient. For a locally limited spectral X-ray image, a highly collimated, i.e., spatially restricted, X-ray beam is also sufficient to reduce the X-ray dose.

[0058] Regardless of whether the tomographic image 40 is based on an ultrasound image dataset or an X-ray or CT image dataset, the determined positioning information can also advantageously be used to generate a virtual 3D view of the needle 41 with respect to the tomographic image 40, including the inclination of the needle 41 relative to the tomographic image 40. Knowledge of the spatial relationship between the needle 41 and the tomographic image 40 can also advantageously be used for navigation and image guidance approaches for navigating the needle 41.

[0059] In Fig. 6, a method for carrying out an advantageous embodiment of the invention is explained. Fig. The procedure described in section 6 corresponds in most steps to the procedure described in Fig. 5. In this respect, the same reference numerals are used and reference is made to the explanations for Fig. 5.

[0060] In addition, in step S7, a further parameter value is determined based on the spectral absorption properties. The further parameter value is assigned to an X-ray marking 21, 26. The X-ray marking 21, 26 is provided on the instrument(s) or needle(s) 41 in addition to the X-ray marker regions 42, 43, 44, 45, 46. The X-ray marking 21, 26 can be superimposed on the X-ray marker regions 42, 43, 44, 45, 46, or can be located beneath them or arranged around them. The spectral absorption properties of the X-ray marking 21, 26 make it possible to identify the instrument(s) or needle(s) 41 and to differentiate them from one another if several are shown in the tomographic image 40.

[0061] The preceding description is intended to include persons with male, female or other gender identities, regardless of the grammatical gender of a particular term.

Claims

[1] Medical instrument (10, 20, 25, 41) for invasive use, comprising an X-ray marker arrangement with at least two X-ray marker areas (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46), characterized by , that the X-ray marker regions (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) are designed such that they each have different absorption properties for X-rays with different energy spectra, that the X-ray marker regions (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) are arranged successively on the instrument (10, 20, 25, 41) with respect to a predetermined spatial direction, and that the X-ray marker areas (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) each have a different metal content. [2] Instrument (10, 20, 25, 41) according to claim 1, wherein the instrument (10, 20, 25, 41) is elongated and the predetermined spatial direction corresponds to the longitudinal direction of the instrument (10, 20, 25, 41). [3] Instrument (10, 20, 25, 41) according to one of the preceding claims, wherein the X-ray marker regions (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) are designed as X-ray markers spatially separated from one another. [4] Instrument (10, 20, 25, 41) according to one of claims 1 to 2, wherein the X-ray marker regions (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) are formed as regions of a one-piece X-ray marker. [5] Instrument (10, 20, 25, 41) according to claim 4, wherein the differences in the absorption properties of the X-ray marker regions (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) for X-ray radiation with different energy spectra change gradually from X-ray marker region (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) to X-ray marker region (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46). [6] Instrument (10, 20, 25, 41) according to one of the preceding claims, wherein in addition to the X-ray marker arrangement, at least one further X-ray marker (21, 26) is provided, which is designed such that it has different absorption properties for X-radiation with different energy spectra, and which is arranged such that it spatially encompasses the X-ray marker arrangement. [7] Computer-implemented method for determining positioning information for an invasive medical instrument (10, 20, 25, 41) according to one of claims 1 to 6, comprising the steps: S1) Receiving a layer image (40) by a computer unit (32), S2) detecting at least one instrument (10, 20, 25, 41) in the tomographic image (40), S3) determining a spatial position of the instrument (10, 20, 25, 41) in the tomographic image (40), S4) receiving an X-ray image data set comprising the spatial position of the instrument (10, 20, 25, 41), which is based on at least two X-ray images generated with X-ray radiation each with a different energy spectrum, S5) Determining a parameter value from the X-ray image data set for the spatial position of the instrument (10, 20, 25, 41), wherein the parameter value depends on the different absorption properties of the instrument (10, 20, 25, 41) or an X-ray marker area (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) of the instrument (10, 20, 25, 41) for X-ray radiation with different energy spectra, characterized by S6) Determining positioning information associated with the respective parameter value, and S8) Outputting the positioning information or information derived from the positioning information via an output device (33). [8] Method according to claim 7, wherein in step 6) the positioning information is obtained from a database (37), and wherein the positioning information is related to the spatial position of a respective X-ray marker area (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) on the instrument (10, 20, 25, 41). [9] Method according to claim 7, wherein in step S5) at least two parameter values ​​are determined for different points at the spatial position of the instrument (10, 20, 25, 41), wherein the parameter values ​​depend on the respective different absorption properties of a respective X-ray marker region (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) of the instrument (10, 20, 25, 41) for X-ray radiation with different energy spectra, wherein in step S6) the positioning information is determined using the at least two parameter values, and wherein the positioning information relates to the spatial positions of the respective X-ray marker areas (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) of the instrument (10, 20, 25, 41) in relation to one another. [10] Method according to one of claims 7 to 9, wherein in step S7) in addition to the parameter value(s) of the instrument (10, 20, 25, 41) or the respective X-ray marker areas (13, ...17, 22, 23, 24, 25, 27, 28, 29, 42, ...46) of the instrument (10, 20, 25, 41), at least one parameter value for an X-ray marking (21, 26) is determined, wherein the parameter value depends on the different absorption properties of the X-ray marking (21, 26) for X-radiation with different energy spectra, and wherein identification information associated with the parameter value is determined, which is related to the identification of the instrument (10, 20, 25, 41). [11] X-ray device with a computer unit which is arranged to carry out the method according to one of claims 7 to 10. [12] A computer program product comprising program elements which are suitable for being read and executed by a computer unit and which, when loaded into a working memory of a computer unit, cause the computer unit to carry out the steps of the method according to any one of claims 7 to 10. [13] A computer-readable storage medium on which program elements are stored which are suitable for being read and executed by a computer unit and which, when loaded into a working memory of the computer unit, cause the computer unit to carry out the steps of the method according to any one of claims 7 to 10.

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