Locating distal end of medical device

Abstract

The distal end (13) of the medical device (1) should be more reliably positioned. For this purpose, a data set is provided which describes the course of the main pipe (6), the course of the first branch pipe (8) from the main pipe (6), and the course of the second branch pipe (9) from the main pipe (6). Furthermore, a course (14, 15) of the medical device (1) in one of the main tube (6) and the first or second branch tube (8, 9) is determined. The course of the main tube (6) and the two branch tubes (8, 9) is registered with respect to the course of the medical device (1). A first similarity measure of the end section (15) to the first branch pipe (8) and a second similarity measure of the end section (15) to the second branch pipe (9) are then calculated. Finally, position information about the distal end (13) of the medical instrument (1) is determined from the similarity measure.

Description

Technical Field

[0001] The invention relates to a method for positioning a distal end of a medical instrument. The invention also relates to a corresponding system having a medical instrument. Background Art

[0002] In some medical fields, blood vessels need to be examined or treated with instruments. For this purpose, the corresponding instrument (e.g. a catheter or a guidewire) must be advanced into the blood vessel. This cannulation is usually performed while observing using an imaging modality. During this process, the position of the tip of the medical instrument in the corresponding blood vessel should be identified.

[0003] The bile duct can also be examined by cannulation (ERCP cannulation: establishing access to the bile duct within the scope of endoscopic retrograde cholangiopancreatography). In this procedure, for example, a so-called guide wire is advanced into the bile duct.

[0004] During ERCP cannulation, it is difficult for the physician to determine whether the tip of the guidewire is located in the common bile duct ("commonbileduct") or in the pancreatic duct ("pancreatic duct" or "ductus pancreaticus"). However, in some cases, the tip of the guidewire may be unintentionally pushed forward. During this step of the procedure, the injection of contrast medium should be avoided in particular, as this increases the risk of complications (particularly pancreatitis). As a result, only the guidewire is visible in the X-ray image, but not the bile duct anatomy. This problem is particularly important clinically, as accidental insertion of the pancreatic duct or injection of contrast medium can lead to a significantly increased risk of complications.

[0005] ERCP procedures are performed approximately 2 million times per year and have a complication rate of 5% to 10% of patients, a large proportion of which are caused during the cannulation procedure, whereby a large number of costly complications can potentially be avoided by improving cannulation guidance. Almost all ERCP procedures are performed using X-ray imaging, but other imaging modalities can in principle also be used.

[0006] The usual approach to cannulation is to advance the guidewire further once the physician no longer feels any resistance. After advancing the guidewire a few centimeters further, an experienced physician can tell from the direction of the guidewire whether it is a pancreatic duct or a common bileduct. In order to visualize the anatomy of the bileduct around the guidewire, contrast medium is injected by less experienced physicians and by physicians experienced in unexpected patient anatomy. If a pancreatic duct is inadvertently inserted, the risk of complications is significantly increased, so preventive treatment for pancreatitis, such as placement of a stent in the pancreatic duct, must be performed immediately. Summary of the invention

[0007] The technical problem to be solved by the present invention is to be able to more reliably position the distal end of a medical device.

[0008] According to the invention, this object is achieved by a method and a system for positioning a distal end of a medical instrument. Advantageous developments of the invention are apparent from the description.

[0009] According to the invention, a method for positioning a distal end of a medical device is therefore provided.

[0010] pass

[0011] - providing a data set describing the course of the main pipe, the course of a first branch pipe from the main pipe (or branching off from the main pipe) and the course of a second branch pipe from the main pipe (possibly from a common branching point);

[0012] - obtaining the course (e.g. line) of the medical device in the main tube and one of the first or second branch tubes;

[0013] - Aligning the orientation of the main tube and the two branch tubes relative to the orientation of the medical device;

[0014] - calculating a first similarity measure between a section of the medical device's course in the first or second branch and a first section of the course of the first branch, and a second similarity measure between a section of the medical device's course in the first or second branch and a second section of the course of the second branch; and

[0015] - Determining position information about a section of the course of the medical instrument (for example the distal end region) from the two similarity measures.

[0016] Therefore, a method for locating the distal end of a medical device is provided. The medical device can be, for example, a catheter, a guide wire, a sphincterotomy device, an endoscope (e.g., "Spyglass") or a part thereof. For example, it can be a guide wire of a sphincterotomy device. The distal end of the medical device is to be located. This means that position information about the distal end or about a section of the medical device at the distal end should be obtained.

[0017] For this purpose, a data set is first provided that describes the direction of the main tube, the direction of the first branch tube from the main tube and the direction of the side branch tube from the main tube. This situation occurs, for example, in the case of a branching of a blood vessel. For example, the main tube is divided into two secondary tubes, i.e. branches. This is the case, for example, for the bile duct channel, which leads from the duodenum to the pancreas and gallbladder. Observing along the flow direction, the "pancreatic duct" and the "common bile duct" open into the "common channel". The common channel then opens into the duodenum.

[0018] But this method can also be used for other branches when for example the main pipe has a plurality of branch pipes that are successively connected and the main pipe itself continues to extend.In this case, these branch pipes are not branches at one point as in the first example, but branch out successively from the main pipe respectively on the position.

[0019] For the corresponding geometry (main pipe with two branches), a data set describing this geometry is provided. In the simplest case, this geometry can be described by three lines arranged in a Y shape. This data set should represent the actual geometry of the main pipe and the branches as accurately as possible. In particular, the angles and lengths of the corresponding components should be specified.

[0020] In a further step of the method, the path of the medical device in the main tube and in one of the first or second branch tubes is acquired. This means that the medical device is located both in the main tube and in one of the branch tubes. In particular, the distal end of the medical device is located in one of the branch tubes. The medical device (e.g. a guide wire) has, for example, a linear path. In this case, the line of the path can be acquired, for example, by a corresponding imaging modality.

[0021] In a further step, the course of the main vessel and the two branch vessels are registered with respect to the course of the medical instrument. This means that the acquired actual course of the medical instrument is registered, for example, to the course of the blood vessel branch (comprising the main vessel and the two branch vessels) previously determined and provided in the data set. For example, the images of the two courses are shifted so that they overlap as much as possible.

[0022] In a further step, a first similarity measure is calculated between a section of the direction of the medical device in the first or second branch and a first section of the direction of the first branch. This means that the degree of similarity between the direction of the medical device at the distal end and the direction of the first section of the data set is investigated. Similarly, a second similarity measure is determined between a section of the direction of the medical device in the first or second branch and a second section of the direction of the second branch. This also means that the degree of similarity between the direction of the distal end of the medical device and the direction of the second branch is determined. Depending on whether the medical device is located in the first branch or the second branch, the similarity measure is correspondingly higher or lower. If the distal end of the medical device is located, for example, on the second branch, the direction of the medical device is more similar to the direction of the second branch than the direction of the first branch. This greater similarity is reflected in the similarity measure.

[0023] Finally, in the method, position information about a section of the direction of the medical device is determined from two similarity measures. This section of the direction of the medical device represents the distal end region of the medical device. The position information can be determined, for example, so that the distal end of the medical device, that is, the relevant section of the direction of the medical device, is assigned to one of the two branches according to the two similarity measures. If the direction of the medical device at its distal end (synonymous with "distal end region" in this article) is more similar to the direction of the first branch, the distal end is assigned to the first branch. This assignment results in position information that the distal end is located in the first branch. However, the position information does not have to be so specific. Instead, the position information can also be the probability that the distal end of the medical device is located in one of the branches.

[0024] The method according to the invention therefore advantageously makes it possible to obtain position information about the distal end of the medical instrument without, for example, using a contrast agent.

[0025] In one embodiment, it is provided that the data set is created from at least one X-ray image, an MRT (magnetic resonance tomography) image, a computed tomography (CT) image and / or an ultrasound scan image. Thus, the geometry of the main vessel and the two branch vessels can be acquired in advance by corresponding imaging. In the medical field, for example, the above-mentioned techniques can be used to reliably identify blood vessel branches.

[0026] In another embodiment, it is provided that the length of the medical instrument is acquired, and the method is only performed when the length of the medical instrument is greater than the length of the direction of the main tube of the data set. Usually, the medical instrument is first inserted into the main tube, and one of the branches is attempted to be probed from the main tube. After the medical instrument completely penetrates the main tube, it is meaningful to explain which branch the medical instrument has probed into. This means that the length of the medical instrument must also be greater than the length of the main tube. For example, the guide wire is guided from the duodenoscope into the "common channel" and is further guided from the common channel into the "pancreatic duct". When the guide wire extends out of the duodenoscope, the extension length of the guide wire can be obtained by the corresponding mark on the guide wire if necessary. If the length reaches a certain extent, it can be considered that the "common channel" has been completely penetrated and the distal end of the guide wire is located in one of the branches. In this case, it is meaningful to perform the method introduced here.

[0027] In another embodiment, the two directions are respective 2D projections. This means that each direction is represented as a two-dimensional shape. The two-dimensional representation reduces the computational and storage costs. However, since it is a projection, possible projection angles that may cause distortions should be taken into account.

[0028] In another embodiment, it is provided that the course of the main pipe and the courses of the two branch pipes are stored as continuous line segments in the data set. That is to say, here too, the complete geometry of the main pipe and the two branch pipes is not stored, but only the corresponding line segments are stored, which in turn reduces the computational and storage outlay. Thus, a typical stored data set can represent, for example, a Y-shaped course structure, i.e., a line segment of the main pipe and two further line segments representing the two branch pipes.

[0029] In a further embodiment, the similarity measure is based on the angle of the section of the path of the medical device in the first or second branch in a preset coordinate system. This coordinate system can be oriented, for example, according to the patient's spine. In an AP (anteroposterior) X-ray projection, the "pancreatic duct" usually extends transversely to the spine, while the "common bileduct" extends parallel to the spine. Depending on which duct the medical device is inserted into, different angles are generated. This angle can be used as a similarity measure. Therefore, the angle or orientation of the distal end of the medical device often already provides a hint of the position of the distal end, i.e., the branch occupied.

[0030] Alternatively or in addition, the similarity measure can be based on the Hausdorff metric between the section of the course of the medical device in the first or second branch and the corresponding section of the course of the corresponding branch. In this case, it is as if the section of the distal end region of the medical device is calculated relative to the corresponding branch. The two courses represent corresponding subsets for calculation, to which the Hausdorff metric is applied. The smaller the distance of the medical device relative to the corresponding course of the branch, the more similar the two courses are or the more likely the medical device is to be located in the corresponding branch.

[0031] In an extended embodiment, it is provided that the probability that the medical device is located in the first or second branch is calculated as position information based on the similarity measure and the probability or a value based on the probability is provided to the user. Thus, the similarity measure can be converted into a probability that the user can better understand. For example, it is shown to the user that the distal end of the medical device is located in the "pancreatic duct" with a probability of 80% and in the "common bileduct" with a probability of only 20%. Thus, the user can better evaluate the next action.

[0032] Furthermore, in one embodiment, it can be provided that a risk measure is determined as a function of the length of the medical device in the first or second branch and the similarity measure and that the risk measure is provided to the user. For example, the risk may increase as the medical device is inserted further into the respective branch. In particular, the risk of inflammation may increase. It is therefore advantageous to provide the user with a corresponding risk factor when guiding the medical device.

[0033] In another embodiment, it is provided that the acquisition of the direction of the medical device is automatically completed by the imaging modality and the data processing device. For example, the corresponding X-ray image, MRT image, CT image or ultrasonic scanning image is obtained by the imaging modality, and these images are further processed by the data processing device. The data processing device can, for example, extract or acquire the direction from the image as a line. In addition, the data processing device can also be designed for image recognition, so as to, for example, recognize a preset line direction.

[0034] As described above, in another embodiment, the length of the medical device can be detected independently of the acquisition of the direction of the medical device and used to calculate the similarity measure. For example, the length of the medical device can be determined based on markings on the medical device. The actual length of the medical device can provide information about distortions that may occur during the acquisition of the image of the medical device. In order to calculate the similarity measure, such distortions need to be taken into account if necessary.

[0035] In different extended designs of the method according to the invention, it can be provided that the corresponding deformation of the first and / or second branch caused by the medical device is determined by a known deformation method, such as EVAR Guidance, and the probability that the medical device is located in the first or second branch is calculated based on the one or more deformations (EVAR=Endovascular Aortic Repair; the method known in EVAR Guidance deforms the superimposed blood vessels based on the shape visible in the imaging of the catheter or medical device located in the blood vessel). When the medical device is inserted into the blood vessel, the deformation of the blood vessel can be determined by the deformation method, for example. The deformation can also optionally be used to determine position information about the medical device or its distal end.

[0036] The above technical problem is also solved according to the present invention by a system, which has

[0037] - medical devices;

[0038] - a storage device designed to provide a data set describing the course of the main pipe, the course of the first branch pipe from the main pipe and the course of the second branch pipe from the main pipe;

[0039] - an imaging modality designed to acquire the course of the medical device in the main tube and in one of the first or second branch tubes;

[0040] -Data processing apparatus, designed for

[0041] * Align the orientation of the main tube and the two branch tubes relative to the orientation of the medical device;

[0042] * calculating a first similarity measure between a segment of the medical device's path in the first or second branch and a first segment of the path of the first branch, and a second similarity measure between a segment of the medical device's path in the first or second branch and a second segment of the path of the second branch; and

[0043] * Determining position information of the segment regarding the course of the medical device from the two similarity measures.

[0044] The advantages and variants explained above with respect to the described method also apply to the system according to the invention in the same manner. Therefore, the individual method steps can also be interpreted as functional features of the corresponding devices of the system.

[0045] The storage device may be a data memory which can store corresponding data sets, for example data sets on the line courses of the main and branch pipes, and can reproduce these data sets as required. The storage device may have its own processor which controls the storage process.

[0046] The medical device can be, for example, a part of a catheter, a sphincterotomy device or a guide wire. If necessary, the medical device can also be a whole catheter, a whole sphincterotomy device or a whole guide wire.

[0047] In one embodiment, the imaging modality comprises an X-ray device, an MRT device or an ultrasound scanning device. The X-ray device may be a C-arm device or an angiography device.

[0048] Furthermore, according to the present invention, a computer program or a computer program product is provided, which comprises instructions, which, when executed by the above system, cause the system to execute the method also described above.

[0049] For application scenarios or application cases which can be derived from the method and are not explicitly described here, provision can be made for outputting a fault message and / or a request for input of user feedback and / or for adjusting a standard setting and / or a predetermined initial state according to the method.

[0050] Regardless of the grammatical gender of a particular term, persons with either male or female gender identities are included. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The invention is further described with reference to the accompanying drawings, in which:

[0052] Figure 1 A schematic view showing an embodiment of a system according to the invention;

[0053] Figure 2 A schematic view showing the course of the main pipe and the two branch pipes as well as the course of the medical device;

[0054] Figure 3 Show Figure 2 The two orientations of are aligned with each other; and

[0055] Figure 4 A schematic block diagram of an embodiment of the method according to the present invention is shown. DETAILED DESCRIPTION

[0056] The examples described in more detail below are preferred embodiments of the present invention.

[0057] The invention is based on the idea of ​​automatically assessing after registration of a data set containing, for example, the bile duct, whether the tip of the guidewire visible in the X-ray image is likely to be located in a “pancreatic duct” or in a “common bile duct”.

[0058] exist Figure 1The system according to the invention is schematically shown in the embodiment of FIG. 1 , which has a medical device 1, a storage device 2, an imaging modality 3 and a data processing device 4. The medical device 1 can be, for example, a duodenoscope, from which a guide wire 5 can be led.

[0059] The medical device 1 is located in the duodenum, more precisely at the entrance of the gallbladder and the pancreas. There, a common channel 6 opens into the duodenum 7. The common channel 6 ("common channel") branches into a common bile duct 8 and a pancreatic duct 9 on the opposite side of the entrance. Generally, the common channel 6 can be called the main duct, the common bile duct 8 can be called the first branch duct, and the pancreatic duct 9 can be called the second branch duct.

[0060] The course of the main tube 6 and the two branches 8 and 9 can be stylized by lines (e.g., center lines). The corresponding line segments can be marked as follows: main tube center line 10, first branch center line (e.g., of the common bile duct) 11, and second branch center line (e.g., of the pancreatic duct) 12. The three line segments 10, 11, and 12 generally form a Y-shape and represent branches.

[0061] exist Figure 1 In the example of FIG. 5 , the guide wire 5 is inserted into the pancreatic duct (second branch 9) through the common channel (main duct 6). The total insertion length L inserted The insertion length L extends from the opening of the main tube 6 to the tip or distal end 13 of the guide wire 5. inserted The length of CC The end section 15 of the guide wire 5 has a length L Ductx .

[0062] The challenge now is to generate position information about in which of the two tube branches 8 and 9 the end section of the medical instrument 1 or the guide wire 5 is located.

[0063] The imaging modality for acquiring the actual course of the medical device 1 or 5 in the main tube 6 and one of the first branch tube 8 and the second branch tube 9 can be designed as an X-ray device, an MRT device, a CT device, an ultrasound scanning device or the like. The imaging modality 3 thus provides, for example, an image of the guide wire 5. A data processing device 4 is connected to the imaging modality 3, which is capable of processing the one or more images of the imaging modality 3. For example, an image processing algorithm can be implemented on the data processing device, which recognizes the guide wire 5 and converts it into a line if necessary.

[0064] In addition, the system has a storage device 2, through which at least one data set can be provided, which describes the direction of the main tube 6, the first branch tube 8 and the second branch tube 9. The storage device 2 provides the data set to the data processing device 4. The data processing device aligns the direction of the main tube 6 and the two branch tubes 8, 9 with the direction of the medical device 1 or 5. For example, the direction of the guide wire 5 is aligned to one or more of the center lines 10, 11 and 12. In addition, the data processing device 4 can calculate a first similarity measure of the first section of the direction of the end section 15 and the first branch tube 8. In addition, the data processing device 4 can also calculate a second similarity measure reflecting the similarity of the end area of ​​the guide wire 5 or the end section 15 with the second section of the direction of the second branch tube 9. Therefore, an objective parameter can be obtained by these similarity measures, which indicates whether the end section 15 or the distal end 13 of the guide wire 5 is located in the first branch tube 8 or the second branch tube 9. Accordingly, the data processing device 4 can also determine position information based on the similarity measure, which provides information about the actual position of the end section 15 of the guide wire 5 .

[0065] Now, the important aspect is to register the previously obtained data set describing the direction of the main tube 6 and the two branch tubes 8, 9 with the record showing the direction of the medical device 1. In this data set, the center lines or midlines of the individual segments (main tube, first branch tube, second branch tube) can be segmented. Then a similarity measure is obtained, which, for example, reflects the distance of the end segment 15 from one of the midlines 11, 12, that is, the distance of the guide wire 5 from one of the registered branch tube midlines. Subsequently, based on this similarity measure, it is estimated in which of the two branches the medical device 1 or the guide wire 5 (with what probability) is located, which is equivalent to the position information.

[0066] Basically, a two-dimensional X-ray system, for example a C-arm, is sufficient as an imaging modality.

[0067] In a specific embodiment, for example, similar to Figure 1 In an example of a cannulation, a guide wire or a catheter (general medical device) is inserted into a cavity (e.g. a bile duct, a blood vessel) of a patient. The hollow organ does not contain any contrast agent and is not radiopaque, at least not radiopaque in the used X-ray system. The loaded image data set (e.g. MRCP) at least programmatically contains visible bile ducts. These bile ducts are segmented (at least centerline segmentation) in a sub-region relevant for cannulation.

[0068] The current direction of the guide wire inserted into the bile duct system and the length of the guide wire are determined. This is performed, for example, by X-ray imaging. The length of the visible guide wire can be determined from the usually clearly visible wall of the duodenum 7. From the wall of the duodenum 7, the guide wire 5 is located in the bile duct that is not X-ray-transparent. It is approximately assumed here that the X-ray projection axis is perpendicular to the axis of that part of the guide wire 5 that is located in the bile duct. Within the scope of the application described herein, this is usually a sufficient approximation.

[0069] The goal now is to automatically obtain position information about which of the two bile duct branches the front part (end section 15) of the guide wire 5 is approximately located. This position information can be automatically provided by algorithmic evaluation. For this purpose, for example, the X-ray opaque line of the end section 15 is compared with the center line of the two bile ducts 8 and 9 ("pancreatic duct" and "common bileduct") or the corresponding subsection of the center line.

[0070] The algorithm evaluation for obtaining position information can be implemented according to the following embodiments. First, the length L of the inserted guide wire segment is (automatically) determined. inserted (See Figure 2 ). If the length L inserted Length L exceeding the common channel 6 CC , that is, the guide wire 5 is also inserted into one of the branch tubes 8, 9, then a method for automatically determining the position information is meaningful and the following steps are performed:

[0071] according to Figure 2 and Figure 3 , the entire guide wire segment 14, 15 (length L inserted ) is aligned with respect to the segment of the main center line 10. This means that the path of the guide wire marked by the line segments 14, 15 is moved to the main center line 10. The projection of the inserted guide wire 5 is now divided into the main section 14 of the guide wire 5 (length L CC ) and an end section 15. For this purpose, a branch point is determined at which the main centerline 10 is divided into a first branch centerline 11 and a second branch centerline 12. The section of the inserted guide wire up to the registered branch point 16 ("bifurcation") corresponds to the main section 14 of the guide wire, and the section from the registered branch point 16 corresponds to the end section 15 of the guide wire (length L Ductx ).

[0072] The course of the medical instrument in the first or second branch 8, 9, i.e. the course of the end section 15, is compared with the course of the two branches 8, 9, i.e. the course of the line segments 11, 12. For this purpose, a similarity measure can be determined by the following calculation method or a combination thereof:

[0073] - Calculate or compare the angles / orientations of corresponding line segments;

[0074] - The line distance is calculated, for example, according to the generalized Hausdorff metric (Hausdorff distance).

[0075] Based on the similarity measure, the probability of detecting one of the two branch pipes 8, 9 can be determined. Alternatively or additionally, the determined length L Ductx Determine your risk assessment. The further you advance in the incorrect channel, the greater the corresponding risk of inflammation.

[0076] For other implementations, we can observe again Figure 1 Here, the length L of the guide wire section in the main tube (main tube section 14) is determined. CC This length can be approximately equal to the length of the main channel (“common channel”) in the segmentation of the pre-interventional data set, for example. If the lateral extension of the main tube is greater or the visible curvature of the guidewire is greater in the X-ray image, the method from the applicant's “EVAR Guidance” can be used to determine the length L Ductx Length L CC The length of the guidewire section (end section 15) in the corresponding branch can thus be determined, for example, by the formula L Ductx =L inserted -L CC Sure.

[0077] In addition, boundary conditions / information, namely having a length L CC The guidewire segment is located in the main tube to adjust the registration of the bile duct, for example by applying the method from "Evar Guidance".

[0078] At this time, the similarity measure can be determined by the following calculation method or a combination thereof:

[0079] - compare angles / orientations of line segments;

[0080] -Hausdorff metric;

[0081] - Aligning the entire guidewire segment 14, 15 both to the combined segment of the center lines 10 and 11 and to the combined segment of the center lines 10 and 12 (if necessary aligning the segment to a length L inserted superior).

[0082] Alternatively, the deformation method for visible tools can again be used in invisible deformable blood vessels. The elastic registration including the smaller deformation of the bile ducts is evaluated as a possible resting position of the end section 15 of the guide wire 5 .

[0083] For example, the distances / metrics (similarity measures) between the intact guidewire segments 14, 15 inserted into the bile duct and the combined centerlines 10, 11 or 10, 12 can be compared. These distance measures are Figure 3 The first distance 17 and the second distance 18 are marked in FIG. In this example, the distance 17 of the guide wire 14, 15 from the center line 10, 11 is greater than the second distance 18 from the combined center line 10, 12. Therefore, the guide wire is located in the second branch 9 with the second branch center line 12 with a higher probability.

[0084] As long as the probability measure is still too uncertain for the physician (i.e., for example, the probability that the end section of the guidewire is in the first branch is only 70%), one of the following steps can be selected in order to increase the confidence in the assignment of the end section 15 to the correct branch (“bileduct”):

[0085] - Advance the guide wire 5 a short distance;

[0086] - Change the X-ray angle and repeat the back recording, as the additional viewing angles introduce additional constraints for the registration.

[0087] Once the probability measure is sufficiently determined from a clinical perspective (eg, there is a 90% probability that the guidewire tip segment is in the "common bile duct"), the physician may advance the guidewire a longer distance and / or inject contrast agent.

[0088] There are some patient anatomies where the "pancreatic duct" and "common bileduct" separate directly at the intestinal wall, so there is (almost) no "common channel". In this case the length of the "common channel" (main tube) can be set to zero: L CC =0.

[0089] The guide wire 5 may have lateral, optically visible length scales / length markings. During the insertion of the guide wire into the bile duct, the length of the guide wire currently advanced into the bile duct may be "counted in" using an optical camera in the duodenoscope or digitally analyzed in the video image. This is used to determine L inserted This information can be used to determine whether the X-ray projection is substantially perpendicular to the axis of the guidewire.

[0090] The guidewire may have radiopaque markings which provide an additional possibility for comparing the actual length of the guidewire with the corresponding length of the guidewire image in the x-ray image. Thus the "viewing angle" for the guidewire segment can be determined.

[0091] Instead of the probability of in which bile duct the end section of the guidewire is located, it is also possible to provide information (without displaying a percentage value) as of a certain probability threshold value as to which bile duct is more likely.

[0092] After the total insertion length of the guidewire is determined by an information source different from the X-ray image, the degree of inclination of the guidewire relative to the X-ray projection axis can be estimated by comparison with the length of the X-ray shadow of the guidewire segment in the X-ray projection image. This can improve the accuracy when performing the method according to the invention and achieve improved 2D / 3D registration of the bile duct based on the current position and shape of the guidewire.

[0093] according to Figure 4 The method flow of an embodiment of the method according to the invention is schematically shown. The first two steps are optional. In a first step S1, the main tube and the first and second branch tubes are recorded by an imaging modality. In step S2, this recording is automatically processed. If necessary, image recognition is performed and / or the center line or midline of the corresponding channel is determined.

[0094] In step S3, a data set representing the main pipe and the branch pipes is provided. This data set comes from the first two steps S1 and S2.

[0095] In a further step S4 , the course of the medical instrument, in particular the course of the center line of the medical instrument, is determined. According to step S5 , the course of the medical instrument can now be registered to the main course of the data set from step S3 .

[0096] After the registration, a similarity measure can be calculated according to step S6, which relates to the similarity of the course of the medical device and the course of the two branches. Finally, according to step S7, position information can be determined based on the similarity measure, which is optionally in the form of a probability that the medical device is located in one of the branches.

Claims

1. A method for positioning a distal end (13) of a medical device (1), It is characterized in that - providing (S3) a data set describing the course of the main pipe (6), the course of the first branch pipe (8) from the main pipe and the course of the second branch pipe (9) from the main pipe; - acquiring (S4) the course of the medical device (1) in the main pipe (6) and in one of the first or second branch pipes (8, 9); - aligning the orientation of the main pipe (6) and the two branch pipes (8, 9) with respect to the orientation of the medical device (S5), - calculating (S6) a first similarity measure (17) between a section (15) of the direction of the medical device (1) in the first or second branch (8, 9) and a first section (11) of the direction of the first branch (8), and a second similarity measure (18) between a section (15) of the direction of the medical device (1) in the first or second branch (8, 9) and a second section (12) of the direction of the second branch (9); and - determining position information about the section (15) of the course of the medical instrument (1) from the two similarity measures.

2. The method according to claim 1, wherein: The data set is created from at least one X-ray image, a magnetic resonance tomography image, a computed tomography (CT) image and / or an ultrasound scan image.

3. The method according to claim 1 or 2, wherein: The length of the medical instrument (1) is determined and the method is performed only when the length of the medical instrument (1) is greater than the length of the course of the main tube (6) of the data set.

4. A method according to any one of the preceding claims, wherein: The directions of the main pipe (6) and the branch pipes (8, 9) are their respective 2D projections.

5. A method according to any one of the preceding claims, wherein: The course of the main pipe (6) and the courses of the two branch pipes (8, 9) are stored in the data set as continuous line segments (10, 11, 12).

6. A method according to any one of the preceding claims, wherein: The similarity measure is based on the angle of a section (15) of the course of the medical instrument (1) in the first or second branch (8, 9) in a predetermined coordinate system.

7. A method according to any one of the preceding claims, wherein: The similarity measure is based on a Hausdorff measure between a section (15) of the course of the medical instrument (1) in the first or second branch (8, 9) and a corresponding section (11, 12) of the course of the corresponding branch (8, 9).

8. A method according to any one of the preceding claims, wherein: Based on the similarity measure, the probability that the medical device (1) is located in the first or second branch (8, 9) is calculated as position information and the probability or a value based on the probability is provided to a user.

9. A method according to any one of the preceding claims, wherein: A risk measure is determined based on the length of the medical device (1) in the first or second branch (8, 9) and the similarity measure and is provided to a user.

10. A method according to any one of the preceding claims, wherein: The acquisition of the direction of the medical device (1) is automatically completed by the imaging modality (3) and the data processing device (4).

11. A method according to any one of the preceding claims, wherein: The length of the medical instrument (1) is detected independently of the determination of the course of the medical instrument (1) and is used to calculate a similarity measure.

12. A system having - Medical devices (1); - a storage device (2) designed to provide a data set describing the course of the main pipe (6), the course of the first branch pipe (8) from the main pipe and the course of the second branch pipe (9) from the main pipe; an imaging modality (3) designed to acquire the course of the medical device (1) in the main tube (6) and in one of the first or second branch tubes (8, 9); - a data processing device (4) designed to - aligning the course of the main tube (6) and the two branch tubes (8, 9) relative to the course of the medical device (1); - calculating a first similarity measure (17) between a section (15) of the direction of the medical device (1) in the first or second branch (8, 9) and a first section (11) of the direction of the first branch (8), and a second similarity measure (18) between a section (15) of the direction of the medical device (1) in the first or second branch (8, 9) and a second section (12) of the direction of the second branch (9); and - determining position information about the section (15) of the course of the medical instrument (1) from the two similarity measures.

13. The system according to claim 12, wherein: The medical device (1) is a part of a catheter, a part of a sphincterotomy, a part of a duodenoscope or a part of a guidewire.

14. The system according to claim 12 or 13, wherein: The imaging modality (3) includes an X-ray device, a magnetic resonance tomography device, a CT device or an ultrasound scanning device.

15. A computer program comprising instructions which, when executed by a system according to any one of claims 12 to 14, cause the system to perform a method according to any one of claims 1 to 11.

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