Position determining device for determining the position of an object in a tubular structure - Patents.com

Abstract

A position determination device, method, and computer program are provided that enable improved determination of the position of an elongate object within a tubular structure. An imaging system including the position determination device, as well as an imaging method and an imaging computer program are also provided. The present invention relates to a position determination device (5) for determining the position of an elongate object (4) within a tubular structure, wherein the position determination device (5) includes a first providing unit for providing a first distribution of curvature values ​​at a plurality of first locations along a path within the tubular structure, a second providing unit (7) for providing a second distribution of strain or curvature values ​​at a plurality of second locations along the object (4), and a position determination unit (8) for determining the position of the object (4) relative to the path based on the first distribution and the second distribution. [Selected Figure] Figure 1

Description

[Technical field]

[0001] The present invention relates to a position determination device, a method and a computer program for determining the position of an elongate object, in particular for determining the position of a medical instrument, such as a catheter, a bronchoscope or a guidewire, in a tubular structure, such as a blood vessel or an airway. The present invention further relates to an imaging system including said position determination device, as well as an imaging method and an imaging computer program. [Background technology]

[0002] In medical applications, positioning devices are known that use electromagnetic (EM) tracking techniques or tracking techniques based on optical shape sensing (OSS) to determine the position of an interventional tool inside a patient's body. Optical shape sensing is typically performed using the evaluation of multiple optical curvature sensors, which consist of multiple strain sensors (stretch sensors) arranged concentrically around the cross section of a fiber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US 2015 / 254526 A1 [Patent Document 2] US 2016 / 302869 A1 [Patent Document 3] US 2014 / 336501 A1 Summary of the Invention [Problem to be solved by the invention]

[0004] However, EM tracking techniques and OSS tracking can be relatively inaccurate due to, for example, inhomogeneities in the EM field and errors in the interpolation and integration of curvature information.

[0005] It is an object of the present invention to provide a position determination device, a method and a computer program which allow an improved determination of the position of an elongate object in a tubular structure. It is a further object of the present invention to provide an imaging system including said position determination device, as well as an imaging method and an imaging computer program. [Means for solving the problem]

[0006] The object is achieved by a position determination device for determining the position of an elongated object (object) in a tubular structure, in particular the position of a medical instrument, the position determination device comprising: - a first providing unit for providing a first distribution of curvature values ​​at a plurality of first locations along a path in the tubular structure; - a second providing unit for providing a second distribution of strain values ​​(elongation values) or curvature values ​​(second distribution information) at a plurality of second locations along the object; a position determining unit for determining a position of the object relative to the path based on the first distribution and the second distribution; Includes. That is, according to the first aspect of the present invention, 1. A position determination device for determining a position of an elongate object within a tubular structure, the position determination device comprising: - a first providing unit for providing a first distribution of curvature values ​​at a plurality of first locations along a path in the tubular structure; - a second providing unit for providing a second distribution of strain or curvature values ​​at a plurality of second locations along the object; - a position determination unit for determining a position of the object relative to its path based on the first distribution and the second distribution; A position determining device is provided, comprising: More specifically, in the first aspect, 1. A position determination device for determining a position within a tubular structure of an elongate object deforming within the tubular structure, the position determination device comprising: - a first providing unit for providing a first distribution of curvature values ​​of the tubular structure at a plurality of first locations along a path within the tubular structure, wherein the first providing unit provides, for the plurality of paths within the tubular structure: each Curvature Value of To provide the first distribution composition That is being done, - a second providing unit for providing a second distribution of strain or curvature values ​​of the object at a plurality of second locations along the object, wherein the second providing unit is adapted to provide a plurality of second distributions along the object for different points in time. composition the plurality of second distributions corresponding to a plurality of positions of the object relative to a path of the tubular structure; - a position determination unit, the position determination unit being configured to: composition That is, - for each route and for each time point 、 determining a distribution of dissimilarity values ​​for different candidate positions of the object for each path, respectively; composition wherein a dissimilarity measure is applied to the first distribution of correspondences and the second distribution of correspondences for various possible candidate positions of the object for the path, the dissimilarity measure resulting in a dissimilarity value for each candidate position of the object for each path that indicates the dissimilarity of both distributions at each candidate position. composition However, at different times and in different candidate locations The method is further developed and provides a map containing corresponding dissimilarity values ​​for different time points and different candidate locations. That it is - Provide route scale composition the route measure providing, for a route through each map ending at one candidate location for the latest time instant and starting at one candidate location for an earlier time instant, a route value that depends on a dissimilarity value along each route; - For each route, the route scale is used to determine the route that has the smallest route value for each route through the map. compositionThus, optimal routes are found for different routes, and therefore for different maps; and - The position of the object relative to one of the paths, Among those optimal routes found, the optimal route with the smallest route value is determined. To decide composition What is being done It is characterized by: According to a second aspect of the present invention, 1. An imaging system, comprising: - a position determination device for determining the position of an elongate object within a tubular structure according to the first aspect; - an imaging unit for providing an image of the tubular structure; - having a visualization generating unit for generating a visualization of the tubular structure based on the provided image and on the determined position, An imaging system is provided, comprising: According to a third aspect of the present invention, 1. A method for determining a position of an elongate object within a tubular structure, the method comprising: - providing, with a first providing unit, a first distribution of curvature values ​​at a plurality of first locations along a path within the tubular structure; - providing, by a second providing unit, a second distribution of strain or curvature values ​​at a plurality of second locations along the object; - determining, by a position determination unit, a position of the object relative to the path based on the first distribution and the second distribution; A method for determining a position is provided. More specifically, in the third aspect, 1. A method for determining a position within a tubular structure of an elongate object deforming within the tubular structure, the method comprising the steps of: - a first providing unit providing a first distribution of curvature values ​​of the tubular structure at a plurality of first locations along a path within the tubular structure, where for the plurality of paths within the tubular structure: each Curvature Value of a first distribution is provided; - a second providing unit providing a second distribution of strain or curvature values ​​of the object at a plurality of second locations along the object, where a plurality of second distributions are provided along the object for different points in time, the plurality of second distributions corresponding to a plurality of positions of the object relative to a path of the tubular structure; - the positioning unit for each path and for each time instant 、 determining a distribution of dissimilarity values ​​for different candidate positions of the object for each respective path, wherein a dissimilarity measure is applied to a corresponding first distribution and a corresponding second distribution for various possible candidate positions of the object for the respective path, the dissimilarity measure resulting in a dissimilarity value for each candidate position of the object for each respective path that is indicative of the dissimilarity of both distributions at the respective candidate position; composition However, at different times and in different candidate locations The method is further developed and provides a map containing corresponding dissimilarity values ​​for different time points and different candidate locations. That it is - providing, by the positioning unit, a route metric, which for a route through each map ends at one candidate location for a latest time instant and starts at one candidate location for an earlier time instant, results in a route value that is dependent on a dissimilarity value along each route, - the positioning unit determines for each path a route which uses the route measures and which, in a route through each map, results in a minimum route value, whereby optimal routes are found for different paths and thus for different maps, respectively; and a position determination unit for determining the position of the object relative to one of the paths; Among those optimal routes found, the optimal route with the smallest route value is determined. determining Contains It is characterized by: According to a fourth aspect of the present invention, 1. A method of imaging, the method comprising: - providing an image of the tubular structure by an image forming unit; - determining the position of an elongate object in a tubular structure by means of a position determination device according to the first aspect; and - generating, by a visualization generating unit, a visualization of the tubular structure based on the provided image and the determined location; An imaging method is provided, comprising: More specifically, in the fourth aspect, 1. An imaging method, the imaging method comprising the steps of: - an imaging unit providing an image of the tubular structure; - determining a position of an elongate object within a tubular structure by means of a position determination device according to the first aspect; and - a visualization generation unit generating a visualization of the tubular structure based on the provided images and on the determined positions, Contains It is characterized by: According to a fifth aspect of the present invention, - a computer program for determining a position of an elongate medical element, the computer program having program code means adapted to provide instructions to a position determining device according to the first aspect to perform the position determining method according to the third aspect when the position determining method according to the third aspect is executed with the position determining device according to the first aspect; A computer program is provided, comprising: According to a sixth aspect of the present invention, an imaging computer program comprising program code means for instructing the imaging system of the second aspect to perform the imaging method of the fourth aspect when the imaging computer program is run on the imaging system of the second aspect; An imaging computer program is provided, comprising: It should be noted that the reference numerals in the claims of the present application are intended solely to facilitate understanding of the present invention and are not intended to limit the present invention to the illustrated forms. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] In the present invention, the following configurations are possible. (Form 1) A position determination device for determining the position of an elongate object, in particular a medical instrument, in a tubular structure, the position determination device comprising: - a first providing unit for providing a first distribution of curvature values ​​at a plurality of first locations along a path in the tubular structure; - a second providing unit for providing a second distribution of strain or curvature values ​​at a plurality of second locations along the object; a position determining unit for determining a position of the object relative to the path based on the first distribution and the second distribution; Contains. (Form 2) Preferably, the first providing unit is adapted to provide, as the first distribution, a scalar distribution of curvature values ​​along a path within the tubular structure. (Form 3) Preferably, the second providing unit is adapted to determine the second distribution based on optical signals of a plurality of optical strain sensors arranged along the object. (Form 4) The position determination unit is - adapted to apply a dissimilarity measure to the first distribution and the second distribution for various possible candidate positions of the object for a path, wherein the dissimilarity measure is adapted to result, for each candidate position of the object for the path, indicative of the dissimilarity of both distributions at the respective candidate position; Preferably, it is adapted to determine the position of the object relative to its path based on the dissimilarity values ​​determined for the different candidate positions. (Form 5) Preferably, the first providing unit is adapted to provide a plurality of first distributions of curvature values ​​for a plurality of paths within the tubular structure, and the position determining unit is adapted to determine a position of the object relative to one of these paths based on the plurality of first distributions and a second distribution. (Form 6) The position determination unit is - for each path, determining a distribution of dissimilarity values ​​for different candidate positions of the object for the respective path; Preferably, it is adapted to determine the position of the object relative to one of the paths based on dissimilarity values ​​determined for the different paths and the different candidate positions. (Form 7) The second providing unit is adapted to provide a plurality of second distributions along the object for different time points, the plurality of second distributions corresponding to a plurality of positions of the object relative to a path of the tubular structure, and the position determining unit is adapted to: - adapted to determine, for each path and for each time point, respectively, a distribution of dissimilarity values ​​for different candidate positions of the object for each path, Preferably, it is adapted to determine the position of the object relative to one of the paths based on dissimilarity values ​​determined for different paths, different time points and different candidate positions. (Form 8) The dissimilarity values ​​determined for different time instants and different candidate positions can be viewed as a map, in which a dissimilarity value is entered for each different location fixed by each time instant and candidate position, and the position determination unit: - adapted to provide a route measure, which for a route through each map ends at one candidate location for a latest time instant and starts at one candidate location for an earlier time instant, results in a route value that is dependent on a dissimilarity value along each route, - adapted to determine, for each path, a route for which a minimum route value is determined for a route through each map using a route measure, whereby optimal routes are found for different paths and thus for different maps, respectively; and Preferably, it is adapted to determine the position of the object for one of the paths based on the optimal routes detected for the different paths, taking into account the route values ​​determined for those optimal routes. (Form 9) Preferably, the position determination unit is adapted to provide a route metric having a component that grows as the sum of dissimilarity values ​​along the respective route increases. (Form 10) The position determination unit is - adapted to detect optimal routes for different time points, whereby optimal routes with corresponding route values ​​are determined for different time points and different routes, respectively, whereby for a route and a given time point, dissimilarity values ​​detected for the given time point and for previous time points and for the candidate positions are used to determine an optimal route with corresponding route values, these dissimilarity values ​​being comprehensible as a map for each route and its given time point; - adapted to select, at each time point, from the plurality of optimal routes found, the optimal route for which a minimum route value has been determined, with the provision that, before the optimal route having the minimum route value is selected, a route value is increased for the optimal route for which, at an earlier time point, a minimum route value has not been determined compared with the route values ​​determined for the other optimal routes, Preferably, it is adapted to determine as the position of the object relative to one of the paths a position defined by the selected optimal route. (Form 11) The position determination unit is adapted to apply a dissimilarity measure according to the following arrangement: - a spatial first gradient distribution of the first distribution is determined; a spatial second gradient distribution of the second distribution is determined; - for each location along the object, a respective gradient of the second distribution is compared with a respective curvature gradient of the first distribution, where each candidate location defines which respective gradient of the second distribution is compared with which respective curvature gradient of the first distribution at each location, where for each location and for each candidate location a sub-dissimilarity measure is used, which sub-dissimilarity measure a) depends on the direction of the gradients relative to each other and / or b) depends on the magnitude of the gradient of the first distribution and the magnitude of the gradient of the second distribution, where by applying the sub-dissimilarity measure for each location a sub-dissimilarity value is determined, Preferably, the lower dissimilarity values ​​that have been determined for a candidate position are summed to determine a respective dissimilarity value for each candidate position. (Form 12) The position determination unit is adapted to apply a dissimilarity measure according to the following arrangement: - local maxima (i.e. local maxima) of the first distribution are determined; - local maxima (i.e. local maxima) of the second distribution are determined; - assigning to each local maximum of the first distribution one local maximum of the second distribution, whereby the sum of all spatial intervals between the assigned local maxima is minimal, with the proviso that each local maximum of the second distribution is assigned to only one local maximum of the first distribution; Preferably, the spatial intervals between the assigned local maxima in the first distribution and the assigned local maxima in the second distribution are added. (Form 13) The position determination unit is adapted to apply a dissimilarity measure according to the following arrangement: - for each location along the object, a respective value of the second distribution is compared with a respective value of the first distribution, where each candidate position defines which respective value of the second distribution is compared with which respective value of the first distribution at each location, where for each location and for each candidate position a sub-dissimilarity measure is used, which sub-dissimilarity measure is zero if a) the respective value of the first distribution is located above a predetermined first threshold, or b) the respective value of the first distribution is located below its first threshold and the respective value of the second distribution is located below a predetermined second threshold, and has a positive value otherwise; Preferably, the lower dissimilarity values ​​that have been determined for a candidate position are added together to determine a respective dissimilarity value for each candidate position. (Form 14) Preferably, the position determination unit is adapted to apply a dissimilarity measure by applying a cross-correlation, in particular a normalized cross-correlation, to the first distribution and the second distribution for each candidate position. (Form 15) 1. An imaging system, comprising: - a position determination device for determining a position of an elongate object within the tubular structure according to claim 1; - an imaging unit for providing an image of the tubular structure; a visualization generating unit for generating a visualization of the tubular structure based on the provided images and on the determined positions; Having. (Form 16) 1. A method for determining a position of an elongate object within a tubular structure, the method comprising: - providing, with a first providing unit, a first distribution of curvature values ​​at a plurality of first locations along a path within the tubular structure; - providing, by a second providing unit, a second distribution of strain or curvature values ​​at a plurality of second locations along the object; determining, by a position determining unit, a position of the object relative to the path based on the first distribution and the second distribution. Contains. (Form 17) 1. A method of imaging, the method comprising: - providing an image of the tubular structure by an image forming unit; - determining the position of an elongated object in a tubular structure by means of a position determination device according to aspect 1; and - generating, by a visualization generating unit, a visualization of the tubular structure based on the provided images and the determined positions. Contains. (Form 18) A computer program for determining the position of an elongated medical element, the computer program having program code means adapted to provide instructions to the position determination device of aspect 1 to perform the position determination method of aspect 16 when the position determination method of aspect 16 is executed with the position determination device of aspect 1. (Form 19) An imaging computer program comprising program code means for instructing the imaging system of aspect 15 to perform the imaging method of aspect 17 when the computer program is run on the imaging system of aspect 15.

[0008] The curvature values ​​of the first distribution at a plurality of first locations along the tubular structure and the strain or curvature values ​​of the second distribution at a plurality of second locations along the object are local values. By determining the position of the object in the tubular structure based on these local information rather than global information, the accuracy of the position determination can be significantly improved since the method is less sensitive to measurement errors. For example, the accuracy of the position determination can be less sensitive, and in particular not sensitive at all, to global measurement errors such as drift, area inhomogeneity, etc. In addition, the position of the object can be determined without a reconstruction of the shape of the object based, for example, on the curvature values ​​of the second distribution being required.

[0009] The first providing unit can be a storage unit in which the curvature values ​​of the first distribution are stored, and the first providing unit can be suitable for providing the stored curvature values ​​of the first distribution. However, the first providing unit can also be a receiving unit for example for receiving the curvature values ​​of the first distribution from the first determining unit and for providing the received curvature values ​​of the first distribution. In addition, the first providing unit can itself be a first determining unit. The second providing unit can also be a storage unit or a receiving unit. Furthermore, the second providing unit can also be a second determining unit.

[0010] The curvature values ​​of the first distribution are preferably predefined. They can be determined based on images of the tubular structure, such as computed tomography images (CT images), magnetic resonance tomography images (MRT images), or other images. The curvature values ​​of the first distribution can also be determined in other ways. For example, in a priori method, one or more curvature sensors can be moved within the tubular structure, so that they are at a known first location within the tubular structure while the curvature of the tubular structure is measured using the curvature sensors. A further example for generating the curvature values ​​is a simulation of the position or orientation of the medical object within the tubular structure extracted from the image data.

[0011] The tubular structure may be, for example, the vascular system, the respiratory system or other branched tubular structures. The tubular structure may also be a technical tubular structure, for example a pipeline system, a tunnel system, a cable channel system, etc. The object is preferably a medical instrument, for example a guidewire, a catheter or a bronchoscope. However, the object may also be a non-medical object, for example to be moved in a pipeline system, in a tunnel system, in a cable duct system, etc.

[0012] In a preferred embodiment, the curvature values ​​of the first and second distributions are scalars, which allows the position of the object in the tubular structure to be determined without using any direction-dependent curvature information. In an embodiment, two local curvatures can be determined at each location in two different directions, for example along the transverse and vertical axes, and both these local curvatures can be combined into one scalar curvature value, which represents the local curvature at each location. For example, a mean curvature value of one scalar or a total Gaussian curvature value of one scalar can be determined. However, the curvature values ​​can also be vector values. For example, both local curvatures, such as the curvature along the vertical axis and the curvature along the transverse axis, can be considered as two-component curvature values ​​at each location.

[0013] The first providing unit is preferably adapted to provide a scalar distribution of curvature values ​​along a path in the tubular structure as the first distribution, while the second providing unit is preferably adapted to provide a distribution of scalar strain values ​​(or elongation values) at a number of second locations along the object as the second distribution, whereby the position determining unit determines the position of the object relative to the path based on the scalar curvature values ​​of the first distribution and the scalar strain values ​​of the second distribution. Since in this situation only the scalar strain values ​​are required, relatively little technical effort is required to determine the position of the object in the tubular structure.

[0014] Furthermore, the second providing unit is preferably adapted to determine the second distribution based on optical signals of a plurality of optical strain sensors (stretch sensors) arranged along the object. The optical strain sensors are preferably integrated in a single optical single-core fiber. At each point along the object, there is preferably only one strain sensor each. This allows the determination of the second distribution of scalar strain values ​​with further reduced technical effort compared to curvature sensors, which technical effort is furthermore relatively easy to handle for the user.

[0015] In another embodiment, when the second distribution is a distribution of curvature values, these curvature values ​​can be determined, for example, using an OSS curvature sensor, or a group of EM or RFID (Radio frequency identification) sensors, where the relative position with respect to other sensors in the sensor group is sufficient for this group of EM or RFID sensors to calculate the local curvature.

[0016] Preferably, Positioning Unita) is adapted to apply a dissimilarity measure to a first distribution and a second distribution for various possible candidate positions of the object relative to a path, where the dissimilarity measure is adapted to result for each candidate position of the object relative to the path indicative of the dissimilarity of both distributions at the respective candidate position, and b) is adapted to determine a position of the object relative to the path based on the determined dissimilarity values ​​for different candidate positions. In one embodiment, the position determination unit is adapted to determine as the position of the object relative to the path the candidate position for which the smallest dissimilarity value has been determined. This already results in a relatively accurate determination of the position of the object relative to the path.

[0017] Furthermore, the positioning device is preferably adapted to provide a plurality of first distributions of curvature values ​​for a plurality of paths in the tubular structure resulting from branching of the structure, the positioning unit being adapted to determine the position of the object relative to one of these paths based on the plurality of first distributions and the one second distribution. In particular, the positioning unit is adapted to a) determine for each path a distribution of dissimilarity values ​​for different candidate positions of the object relative to the respective path, and b) determine the position of the object relative to one of the paths based on the determined dissimilarity values ​​for the different paths and the different candidate positions. This allows for an accurate determination of the position of the object relative to one of the paths when the tubular structure has a plurality of possible paths along which the object could be located.

[0018] It is further preferred that the second providing unit is adapted to provide a plurality of second distributions along the object for different points in time, wherein these plurality of second distributions correspond to a plurality of positions of the object relative to one path of the tubular structure, and further wherein the position determining unit is adapted a) to determine, for each path and for each point in time, respectively, a distribution of dissimilarity values ​​for different candidate positions of the object relative to each path, and further b) to determine a position of the object relative to one of the paths based on the dissimilarity values ​​determined for the different paths, the different points in time and the different candidate positions. In particular, the dissimilarity values ​​determined for different time instants and different candidate positions can be considered as a map, in which different locations fixed by the respective time instants and candidate positions are respectively filled with dissimilarity values, and the positioning unit is adapted to a) provide a route measure which, for a route through each map ending at one candidate position for the latest time instant and starting at one candidate position for an earlier time instant, results in a route value depending on the dissimilarity values ​​along the respective route, b) for each route, use the route measure to determine, for a route through each map, a route for which the smallest route value is determined, whereby optimal routes are found for the different routes and thus for the different maps, respectively, and c) to determine the position of the object for one of the routes on the basis of the optimal routes found for the different routes, taking into account the route values ​​determined for the optimal routes. The positioning unit is preferably adapted to provide a route measure having a component which increases as the sum of the dissimilarity values ​​along the respective route increases. In one embodiment, the position determining unit is adapted to determine as the position of the object relative to one of the paths the position defined by the route having the lowest route value of all the optimal routes, which results in a further improved determination of the position of the object within the tubular structure.

[0019] However, it is also preferred that the position determination unit is adapted a) to detect optimal routes for different time points, whereby optimal routes with corresponding route values ​​are determined for different time points and different routes, respectively, whereby for a route and a given time point, the detected dissimilarity values ​​for the given time point and for the previous time points and for the candidate positions are used to determine an optimal route with corresponding route values, whereby these dissimilarity values ​​can be understood as a map for each route and for the given time point, b) to select from the detected optimal routes at each time point the optimal route for which the smallest route value has been determined, whereby the route value is increased for the optimal route for which the smallest route value has not been determined at the previous time point compared to the route values ​​determined for the other optimal routes, before the optimal route with the smallest route value is selected, and c) to determine the position defined by the selected optimal route as the position of the object for one of the routes, which leads to a further improved accuracy of the determination of the position of the object in the tubular structure.

[0020] The position determination unit may be adapted to apply the dissimilarity measure by: a) determining a spatial first gradient distribution of the first distribution; b) determining a spatial second gradient distribution of the second distribution; c) for each location along the object, a respective gradient of the second distribution is compared with a respective curvature gradient of the first distribution, wherein each candidate location defines which respective gradient of the second distribution is compared with which respective curvature gradient of the first distribution at each location; further wherein for each location and for each candidate location, a sub-dissimilarity measure is used, which sub-dissimilarity measure i) depends on the direction of the gradients of each other and / or ii) depends on the magnitude of the gradient of the first distribution and the magnitude of the gradient of the second distribution, wherein a sub-dissimilarity value is determined by applying the sub-dissimilarity measure for each location; and d) the sub-dissimilarity values ​​determined for one candidate location are summed to determine a respective dissimilarity value for each candidate location. In one embodiment, the value of the sub-dissimilarity measure decreases as the similarity of both gradients in the direction of each other increases. This decrease can be monotonic and / or continuous. Furthermore, in one embodiment, the sub-dissimilarity measure yields a first value if the magnitude of the gradient of the first distribution is smaller than a first magnitude threshold and the magnitude of the gradient of the second distribution is smaller than a second magnitude threshold, and a second value if the magnitude of the gradient of the first distribution is not smaller than the first magnitude threshold and / or the magnitude of the gradient of the second distribution is not smaller than the second magnitude threshold, with the first value being smaller than the second value. The sub-dissimilarity measure can also have both components, i.e. the first component yields a value that decreases as the similarity of the gradients increases, and the second component yields a smaller value if the magnitude of the gradient of the first distribution is smaller than the first magnitude threshold and the magnitude of the gradient of the second distribution is smaller than the second magnitude threshold, and a larger value otherwise. The first and second components can, for example, be combined linearly, which includes simple addition, or both components can be combined non-linearly.In one embodiment, both components are combined multiplicatively, the result of this combination being a single scalar value for the lower-level dissimilarity measure.

[0021] In a further embodiment, the value of the lower-level dissimilarity measure decreases as the magnitude of the gradients of the first and second distributions decreases, i.e. the value decreases when both magnitudes of both gradients decrease. The decrease can be monotonic and / or continuous. The value can also be linearly or non-linearly combined with the value of said first component. For example, the value can be multiplied with said first component or the values ​​can be added.

[0022] However, the position determination unit can also be adapted to apply the dissimilarity measure by: a) determining local maxima (local maxima) of the first distribution, b) determining local maxima (local maxima) of the second distribution, c) assigning one local maximum of the second distribution to each local maximum of the first distribution, whereby the sum of all spatial intervals between the assigned local maxima is minimal, whereby each local maximum of the second distribution is assigned to only one local maximum of the first distribution, and d) adding up the spatial intervals between the assigned local maxima in the first distribution and the assigned local maxima in the second distribution. The position determination unit may further be adapted to apply a dissimilarity measure by: a) for each location along the object, a respective value of the second distribution is compared with a respective value of the first distribution, with each candidate position defining which respective value of the second distribution is compared with which respective value of the first distribution at each location, with each candidate position defining which respective value of the second distribution is compared with which respective value of the first distribution, with each location and each candidate position using a sub-dissimilarity measure which is i) zero if the respective value of the first distribution is located above a predefined first threshold, or ii) if the respective value of the first distribution is located below its first threshold and the respective value of the second distribution is located below a predefined second threshold, and has a positive value otherwise, and b) the sub-dissimilarity values ​​determined for a candidate position are summed to determine a respective dissimilarity value for each candidate position. It has been found that the use of these dissimilarity measures allows a further improvement in the determination of the position of the object in the tubular structure. Of course, however, other dissimilarity measures can also be used.

[0023] The position determination unit may also be adapted to apply a dissimilarity measure by applying a cross-correlation, in particular a normalized cross-correlation, to the first distribution and to the second distribution for each candidate position. In particular, the position determination unit may determine a mean value E of the distortion or curvature value of the second distribution. D, the mean value of the curvature values ​​of the first distribution E T , the standard deviation σ of the skewness or curvature values ​​of the second distribution D , the standard deviation of the curvature values ​​of the first distribution σ T , and finally, is adapted to calculate the normalized cross-correlation according to the following formula:

[0024] TIFF0007660375000001.tif2094

[0025] where n is the number of curvature values ​​of the first distribution and the number of distortion or curvature values ​​of the second distribution, where index i indicates each of the curvature values ​​of the first distribution and each of the curvature values ​​of the second distribution, where D(i) indicates each of the distortion or curvature values ​​of the second distribution and T(i) indicates each of the curvature values ​​of the first distribution. The distortion or curvature value D(i) of the second distribution and the curvature value T(i) of the first distribution are each the i-th value, and these values ​​overlap at each candidate position. For different candidate locations, the first and second distributions are shifted differently with respect to each other, so that for different candidate locations, different first locations of the first distribution overlap with different second locations of the second distribution, which typically results in different distortion or curvature values ​​of the second distribution and also the curvature values ​​of the first distribution, and thus different normalized cross-correlations are obtained for different candidate locations. It has been found that by using this dissimilarity measure based on normalized cross-correlation, the determination of the location of an object in a tubular structure can be further improved.

[0026] The above object is further achieved by an imaging system, the imaging system comprising: - a position determination device for determining the position of an elongate object within the tubular structure according to claim 1; - an imaging unit for providing an image of the tubular structure; a visualization generating unit for generating a visualization of the tubular structure based on the provided images and on the determined positions; has.

[0027] The above object is further achieved by a method for determining a position, the method comprising: - providing, with a first providing unit, a first distribution of curvature values ​​at a plurality of first locations along a path within the tubular structure; - providing, by a second providing unit, a second distribution of strain or curvature values ​​at a plurality of second locations along the object; determining, by a position determining unit, a position of the object relative to the path based on the first distribution and the second distribution. Includes.

[0028] The above problems are further solved by an imaging method, the imaging method comprising: - providing an image of the tubular structure by an image forming unit; - determining the position of an elongated object in a tubular structure by means of a position determination device according to claim 1; and - generating, by a visualization generating unit, a visualization of the tubular structure based on the provided images and the determined positions. Includes.

[0029] The above problem is further solved by a computer program for determining the position of an elongated object, the computer program comprising: 10 When the position determination method according to claim 1 is executed by the position determination device according to claim 1, 10 The position determining device according to claim 1 further comprises program code means adapted to instruct the position determining device according to claim 1 to carry out the position determining method according to claim 1.

[0030] The above problem is further solved by an imaging computer program, which comprises the steps of: 9 When implemented in the imaging system of claim 11 In order to carry out the imaging method according to claim 9 and program code means for instructing the imaging system of claim 1.

[0031] The position determination device according to claim 1, 9 The imaging system according to claim 10 The position determination method according to claim 11 The imaging method according to claim 12 The computer program according to claim 1 13 It is to be understood that the imaging computer program described in has similar or identical embodiments, which are particularly defined in the dependent claims.

[0032] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. [Brief description of the drawings]

[0033] [Figure 1] FIG. 1 is a diagram illustrating a schematic diagram of an embodiment of an imaging system. [Diagram 2] FIG. 1 shows a flow chart illustrating one embodiment of an imaging method. [Diagram 3] FIG. 2 illustrates an image of one tubular structure. [Figure 4] FIG. 4 illustrates one vessel graph representing a tubular structure and extracted from the image shown in FIG. 3. [Diagram 5] 1 illustrates different first distributions of curvature values ​​for different paths within a tubular structure. [Figure 6] FIG. 1 illustrates a distribution of dissimilarity values ​​for different candidate locations and a path. [Figure 7] FIG. 1 illustrates dissimilarity values ​​for different candidate locations and times for a path within a tubular structure, whereby a map is constructed. [Figure 8] FIG. 8 illustrates an optimal route through the map shown in FIG. 7. [Figure 9] FIG. 1 illustrates various cost curves. EXAMPLES

[0034] Fig. 1 illustrates diagrammatically an embodiment of an imaging system 1 including a positioning device 5 for determining a position of the instrument 4 in the tubular structure, an image-forming unit 10 for providing an image of the tubular structure and a visualization-generating unit 11 for generating a visualization of the tubular structure based on the provided image and the determined position. In this embodiment, the tubular structure is a vascular structure of a patient 3 positioned on a patient couch 2. The positioning device 5 includes a first providing unit 6 for providing curvature values ​​indicative of the curvature of the tubular structure at a plurality of first locations along the tubular structure, the first providing unit 6 in this embodiment being suitable for determining the curvature values ​​based on images provided by the image-forming unit 10. In particular, the image-forming unit 10 is suitable for providing a three-dimensional image of the tubular structure, for example a computed tomography image or a magnetic resonance image, which may have been recorded before the insertion of the instrument 4 in the patient 3, i.e. the provided image may be a pre-intervention three-dimensional image. The first providing unit 6 may be adapted to segment tubular structures in the provided image and to determine curvature values ​​based on the segmentation of the tubular structures in the image, these curvature values ​​being local curvature values ​​and constituting a first distribution (first distribution information).

[0035] In this embodiment, the instrument 4 (object of interest) is a catheter having optical strain sensors (stretch sensors) at a number of second locations along the catheter 4. The positioning device 5 includes a second providing unit 7 for providing strain values ​​(stretch values) based on the optical signals received from the strain sensors. The strain values ​​are scalar quantities and indicative of the strain at the respective second locations and are therefore local strain values.

[0036] The positioning device 5 further comprises a positioning unit 8 for determining the position of the instrument 4 within the tubular structure based on the first curvature value and the second distortion value. In this embodiment, these first and second values ​​are scalar quantities. In particular, at one given spatial location, two local curvatures of the tubular structure can be determined in two different directions and both local curvatures can be combined into one scalar curvature value, which is indicative of the local curvature at the respective spatial location. For example, the average curvature value of the one scalar quantity can be determined according to the following formula:

[0037] TIFF0007660375000002.tif2253

[0038] On this occasion, K m is the scalar mean curvature value, and k1 and k2 are the local curvatures in both different directions. Furthermore, the (Gaussian) curvature value K t can be calculated according to the following formula:

[0039] TIFF0007660375000003.tif1951

[0040] The variables k1 and k2 can be considered as the principal curvatures of, for example, the tubular structure, i.e. the eigenvalues ​​of the Formoperator of the tubular structure at each location.

[0041] The positioning unit 8 is adapted to apply a dissimilarity measure to the first distribution and the second distribution for various possible candidate positions of the catheter 4 for a path (passageway), where the dissimilarity measure is adapted to result in a dissimilarity value for each candidate position of the catheter 4 for the path, which is indicative of the dissimilarity of both distributions at the respective candidate position. The positioning unit 8 is further adapted to determine a position of the catheter 4 for the path based on the determined dissimilarity values ​​for the different candidate positions. The positioning unit 8 may for example be adapted to determine the candidate position for which the smallest dissimilarity value is determined as the position of the catheter 4 for the path.

[0042] Furthermore, the positioning device is adapted to determine the position of the catheter 4 in the tubular structure also when the tubular structure has a plurality of paths. In particular, the first providing unit 6 is adapted to provide a plurality of first distributions of curvature values ​​for a plurality of paths in the tubular structure, the positioning unit 8 then being adapted to determine the position of the catheter 4 for one of these paths on the basis of the plurality of first distributions and on the basis of a second distribution. Preferably, the positioning unit 8 is adapted to determine for each path a distribution of dissimilarity values ​​for different candidate positions of the catheter 4 for the respective path and to determine the position of the catheter 4 for one of the paths on the basis of the dissimilarity values ​​determined for the different paths and the different candidate positions.

[0043] The second providing unit 7 is further adapted to provide a plurality of second distributions along the catheter 4 for different time points, where these second distributions correspond to a plurality of positions of the catheter 4 for one path of the tubular structure. The positioning unit 8 is adapted to determine for each path and for each time point, respectively, a distribution of dissimilarity values ​​for different candidate positions of the medical instrument for the respective path and to determine a position of the catheter 4 for one of the paths based on the determined dissimilarity values ​​for the different paths, the different time points and the different candidate positions. In particular, the determined dissimilarity values ​​for the different time points and the different candidate positions can be considered as a map, where in this map, for different locations fixed by the respective time points and the candidate positions, respectively dissimilarity values ​​are entered. The positioning unit 8 is then adapted to provide a route measure which, for a route through the respective map, results in a route value that is dependent on the dissimilarity values ​​along the respective route for a route that ends at a candidate position for the latest time point and starts at a candidate position for an earlier time point. The positioning unit 8 is further adapted to determine, for each path, a route for which a minimum route value is determined for a route through the respective map using the route measure, whereby optimal routes are detected for the different paths, respectively. The positioning unit 8 is further adapted to determine a position of the catheter 4 for one of the paths based on the optimal routes detected for the different paths, taking into account the route values ​​determined for those optimal routes.

[0044] In particular, the positioning unit 8 is adapted to provide a route metric that grows as the sum of the dissimilarity values ​​along the respective routes increases. Further, the positioning unit 8 is preferably adapted to determine as the position of the catheter 4 for one of the paths the position defined by the route having the lowest route value among all the optimal routes.

[0045] Furthermore, the positioning unit 8 is preferably adapted to detect optimal routes for different time points, whereby optimal routes with corresponding route values ​​are determined for different time points and for different routes, respectively, whereby for a route and a given time point, the detected dissimilarity values ​​for the given time point and for the previous time point and for the candidate positions are used to determine an optimal route with corresponding route values ​​for the given time point and for the previous time point, whereby these dissimilarity values ​​can be understood as a map for each route and for the given time point. Furthermore, the positioning unit 8 is preferably adapted to select, from the detected optimal routes, at each time point, the optimal route for which the smallest route value has been determined, whereby the route value is increased for the optimal route for which the smallest route value has not been determined at the previous time point compared to the route values ​​determined for the other optimal routes, before the optimal route with the smallest route value is selected. Furthermore, the positioning unit 8 is preferably adapted to determine the position defined by the selected optimal route as the position of the catheter 4 for one of the routes.

[0046] To determine the dissimilarity value, the positioning unit 8 can be adapted to calculate the gradient of the measured strain sensor profile and the gradient of the curvature profile of the tubular structure. The positioning unit 8 can thus be adapted to apply a dissimilarity measure, whereby a spatial first gradient distribution of the first distribution and a spatial second gradient distribution of the second distribution are determined. The positioning unit 8 is further adapted to compare, for each location along the catheter 4, the respective gradient of the second distribution with the respective curvature gradient of the first distribution, whereby each candidate location defines which respective gradient of the second distribution is compared with which respective curvature gradient of the first distribution at each location, whereby for each location and for each candidate location a sub-dissimilarity measure is used, which sub-dissimilarity measure decreases as the similarity of the mutual orientation of the gradients increases. This decrease with increasing similarity can be, for example, monotonic. Alternatively or additionally, the sub-dissimilarity measure may yield a smaller value if the gradient magnitude of the first distribution is smaller than a predefined first magnitude threshold and the gradient magnitude of the second distribution is smaller than a predefined second magnitude threshold, and a larger value otherwise. The sub-dissimilarity measure may thus have at least one or at least two components, with the first component yielding a value that decreases as the similarity of the gradient directions increases, and / or the second component yielding a smaller value if the gradient magnitude of the first distribution is smaller than a predefined first magnitude threshold and the gradient magnitude of the second distribution is smaller than a predefined second magnitude threshold, and a larger value otherwise. That is, for all matching gradient values ​​a penalty term is calculated, which is high if a) both gradients point in dissimilar directions and / or b) neither of both gradients is small, and a comparison with a corresponding magnitude threshold is used to determine whether each gradient value is small.

[0047] By applying the sub-dissimilarity measure, for each location a sub-dissimilarity value is determined. Furthermore, the position determination unit 8 is adapted to sum up the sub-dissimilarity values ​​determined for a candidate position to determine a respective dissimilarity value for each candidate position. That is, the sum of all penalty terms is a measure for the match of the curvature profile and the strain sensor profile.

[0048] The positioning unit 8 may also be adapted to apply other dissimilarity measures, whereby local maxima of the first distribution and local maxima of the second distribution are determined. That is to say, the positioning unit 8 may be adapted to find all local maxima in the strain sensor profile and the curvature profile. In this case, the positioning unit 8 may further be adapted to assign one local maximum of the second distribution to each local maximum of the first distribution, whereby the sum of all spatial intervals between the assigned local maxima is minimal, whereby each local maximum of the second distribution is assigned only to one local maximum of the first distribution. In addition, the positioning unit 8 may, for example, be adapted to apply a brute force approach for the assignment. In this case, the positioning unit 8 may further be adapted to add up the spatial intervals between the assigned local maxima in the first distribution and the assigned local maxima in the second distribution in order to determine the dissimilarity value.

[0049] However, the location determination unit 8 can also be adapted to apply a dissimilarity measure for each location along the catheter 4, whereby a respective value of the second distribution is compared with a respective value of the first distribution, with each candidate location defining which respective value of the second distribution is compared with which respective value of the first distribution at each location, whereby for each location and for each candidate location a sub-dissimilarity measure is used, which is zero if a) the respective value of the first distribution lies above a predefined first threshold, or b) the respective value of the first distribution lies below its first threshold and the respective value of the second distribution lies below a predefined second threshold, and otherwise results in a positive value. This is based on the observation that a zero point of the curvature in the first distribution results in a corresponding zero point in the distortion measurement. This dissimilarity measure can also be considered as an injective zero-point comparison, where a binary convolution between the small curvature and small distortion values ​​is calculated, and the sub-dissimilarity values ​​determined for one candidate position are summed again to determine a respective dissimilarity value for each candidate position.

[0050] The position determination unit 8 may also be adapted to apply a dissimilarity measure by applying a cross-correlation, in particular a normalized cross-correlation, to the first distribution and to the second distribution for each candidate position. In particular, the position determination unit 8 may be adapted to apply a dissimilarity measure by applying a mean value E D , the mean value of the curvature values ​​of the first distribution E T , the standard deviation of the distortion values ​​σ D , the standard deviation of the curvature values ​​σ T , and finally, it may be adapted to calculate the normalized cross-correlation according to the following formula:

[0051] TIFF0007660375000004.tif2391

[0052] In this case, n is the number of curvature values, and therefore in this example also the number of distortion values, with the index i indicating the individual curvature values ​​and the individual distortion values, with D(i) indicating the respective distortion value and T(i) indicating the respective curvature value. The distortion value D(i) and the curvature value T(i) are each the i-th value, which are overlapped at each candidate position. Since the first distribution and the second distribution are shifted differently with respect to each other for different candidate positions, different first locations of the first distribution and different second locations of the second distribution are overlapped for different candidate positions, whereby typically different distortion and curvature values ​​are also overlapped, and therefore different normalized cross-correlations are obtained for different candidate positions. In this example, the dissimilarity measure is or depends on the normalized cross-correlation.

[0053] The visualization generating unit 11 is suitable for generating a visualization of the tubular structure based on the provided image and the determined position of the instrument 4 in the tubular structure, such that the determined position of the instrument 4 is visualized in the provided image or in a further image obtained from the image provided by the imaging unit and showing the desired structure in the patient. The imaging system 1 further comprises an output unit 13, such as a display, for displaying the visualization to the user, and an input unit 12, such as a keyboard, a computer mouse, a touchpad, etc. Thereby, while the instrument 4 is in the tubular structure of the patient 3, the user can see exactly where the instrument 4 is in the tubular structure, which helps the user in using the instrument 4 inside the patient's body. For example, the instrument 4 can have sensing properties (functions) and / or treatment properties (functions), and the displayed visualization can assist the user in performing the sensing and / or treatment method, by displaying on the output unit 13 the exact position of e.g. the tip of the instrument 4 relative to the tubular structure.

[0054] In the following, one embodiment of an imaging method will be described, by way of example, with reference to the flow chart shown in FIG.

[0055] In step 101, an image of the tubular structure is provided by the image forming unit 10, and in step 102, curvature values ​​indicative of the curvature of the tubular structure at a plurality of first locations along the tubular structure are provided by the first providing unit 6. The first providing unit 6 thus provides a first distribution (first distribution information). These curvature values ​​can be provided before, during or after the insertion of the instrument 4 into the tubular structure of the patient 3. After the instrument 4 has been inserted into the tubular structure of the patient 3, in step 103, strain values ​​indicative of the strain (elongation) of the instrument 4 at a plurality of second locations along the instrument 4 are provided by the second providing unit 7. The second providing unit 7 thus provides a second distribution (second distribution information). In step 104, a position of the instrument 4 within the tubular structure is determined by the position determination unit 8 based on the first distribution and the second distribution, and in step 105 a visualization of the tubular structure is generated by the visualization generation unit 11 based on the provided image and the determined position, wherein the generated visualization is displayed on the output unit 13 in step 106. Steps 102 to 104 can be considered as steps of a position determination method for determining a position of an instrument within a tubular structure.

[0056] The above-described positioning device enables internal tubular navigation based on strain profiles determined using multiple fiber optic strain sensors, which may be incorporated into medical instruments such as catheters, guidewires, bronchoscopes, or other medical instruments.

[0057] The described localization devices and also the localization methods are preferably adapted in such a way that they allow a possible correlation of the distortion measurements with a given tube-shaped structure in real time. The tube-shaped structure is preferably extracted from the pre-intervention image data, whereby a scalar curvature profile of the medical instrument is determined for each possible path through the tube-shaped structure based on the extracted tube-shaped structure. This can be done, for example, by extraction of the respective vessel centerline or by biophysical simulation of the expected position or orientation of the instrument in the vessel. These multiple curvature profiles for multiple paths can subsequently be used as a first distribution in the mapping step during the intervention.

[0058] During the intervention, a strain profile of the medical instrument is determined, i.e. the second distribution, and correlated with the pre-determined curvature profile, i.e. the first distribution, whereby a distance measure, i.e. a dissimilarity measure, between the strain profile and the respective curvature profile is preferably selected such that a non-linear relationship between curvature and strain is taken into account.

[0059] If a strain profile along the medical device is used as the second distribution, it is not necessary to determine a curvature profile based on at least two strain profiles in order to determine, for example, a three-dimensional shape of the medical device, which may be imaged on the tubular structure based on the curvature profile, whereby a single optical fiber or a single optical fiber core with multiple strain sensors (stretch sensors) is sufficient to determine the position of the medical device, which can be manufactured at relatively low cost and can also be relatively easily integrated into the medical device.

[0060] Figure 3 illustrates a three-dimensional image of a tubular structure, and Figure 4 illustrates a vascular graph 31 that is generated based on the image shown in Figure 3 and represents the tubular structure. The vascular graph 31, and therefore the tubular structure, is branched and not cyclic.

[0061] FIG. 5 illustrates, by way of example, four curvature value profiles 32-35 for four paths in a tubular structure, with the curvature K plotted along the vertical axis and the respective points x along the respective paths plotted along the horizontal axis. For each point along the corresponding path, a local curvature is calculated based on the tubular structure, with various paths being obtained due to branching in the tubular structure, which paths can also be called vascular tree paths (GBPs). The local curvature is preferably determined along all GBPs. FIG. 5 thus shows a number of first distributions.

[0062] Strain sensors (strain sensors) arranged along the medical device are used to determine point-by-point strain values ​​(strain values) that can be correlated with the curvature of the tubular structure. It should be noted that depending on the orientation of the optical fibers with respect to the respective paths, the individual local strain sensors may not be affected by the curvature of the paths. This is especially the case when the curvature is perpendicular to the position axis of the strain sensors in the medical device. Nevertheless, an accurate determination of the position of the medical device in the tubular structure is possible using the present positioning device and method.

[0063] Preferably, the position determination unit 8 determines in a first step the most likely position of the medical device for each possible GBP, whereby for each possible position of the medical device along a GBP, i.e. for each candidate position, the curvature values ​​along the respective first distribution of the respective GBP and the measured strain values ​​in the medical device are compared with respect to a distance measure, i.e. a dissimilarity measure. Various distance measures are conceivable, whereby for each possible distance measure or dissimilarity measure, a characteristic of the curvature and strain profile, i.e. a characteristic of the first distribution and the second distribution, is extracted and based on these characteristics, a distance, i.e. a dissimilarity value, of the first distribution and the second distribution is determined for a given candidate position. Thus, for each GBP passing through the tubular structure, a plausibility or dissimilarity value of each possible position of the medical device along the respective GBP, i.e. a plausibility or dissimilarity value of each candidate position is obtained. FIG. 6 illustrates, by way of example, the plausibility or dissimilarity values ​​for different candidate positions p as different grey values.

[0064] In one embodiment, the most likely candidate location of the medical instrument within one given GBP can be taken as the candidate location for which the smallest dissimilarity value is determined, i.e. the candidate location for which the smallest distance is determined. However, such a location determination may be erroneous, for example due to noise, so that preferably information about the past time point is simultaneously incorporated into the determination of the most likely candidate location. That is to say, preferably, for each GBP and for each time point, respectively, a distribution of dissimilarity values ​​is determined for different candidate locations of the medical instrument for each GBP, whereby a map illustrated in FIG. 7 is obtained, which may also be called an energy map (EKP).

[0065] Also in Fig. 7, different dissimilarity values ​​of the EKP38 are illustrated with different grey values, where the EKP38 is developed with different candidate positions p and different times t. That is, the EKP38 contains corresponding dissimilarity values, which are illustrated with grey levels in Fig. 7, for different candidate positions p and different times t. The most likely position of the medical instrument in one GBP is then preferably obtained by an optimal route (Weg) through the EKP38. Optimal here means that the accumulated dissimilarity value along the route through the EKP38 is preferably the smallest, optionally taking into account regularity conditions. The optional regularity conditions could take into account, for example, that the route through the EKP38 should be as short as possible. It could also be taken into account that the route through the EKP38 should be as straight as possible. Technically, each route through the EKP38 is associated with a certain cost, which is obtained from the accumulated dissimilarity value and the optional regularity. The route with the lowest cost is the optimal route defining the location of the medical instrument for one GBP and for different times.In FIG. 8, such an optimal route 39 is exemplarily illustrated.

[0066] Now, from the most plausible position for each GBP, the position of the medical instrument in the entire tubular structure is determined. For this purpose, the optimal EKP-cost-values ​​of the individual GBPs, i.e. the route values ​​of the optimal routes, are compared with each other. In an embodiment, the GBP with the lowest route value and the corresponding most plausible position are selected. However, this approach is also noisy, which may lead to erroneous decisions, especially since the finally determined position of the medical instrument jumps here and there between the GBPs. To prevent this, a time regularization is preferably used, which penalizes jumps between the GBPs. For this purpose, the time course of the optimal route values ​​for each GBP is stored, for example as an optimal cost curve (OKK). Such OKKs 40-42 are illustrated in FIG. 9. FIG. 9 illustrates OKKs 40-42 with different optimal route values ​​W for different times t.

[0067] The time regularization is based on adding a penalty term to all OKKs that were not the smallest at an earlier time point. In FIG. 9, this penalty term is symbolized, for example, by a double arrow 45. Curve 44 is based on OKKs 41 after the penalty term 45 has been added, and curve 43 is based on OKKs 42 after the penalty term has been applied. The penalty term is preferably simply an additive value that is predetermined and can be determined beforehand, for example within the scope of the calibration of the system. Also the above-mentioned threshold and magnitude threshold can be determined beforehand within the scope of the calibration. Thus, as described above, the position determination unit is preferably adapted to select, at each time point, from the detected optimal routes, the optimal route for which a minimum route value has been determined, the route value being increased for optimal routes for which a minimum route value has not been determined at an earlier time point, compared to the route values ​​for which other optimal routes have been determined, before the optimal route with the minimum route value is selected. The determined current position of the catheter in the tubular structure is marked with an X in FIG. 8.

[0068] Although in the above embodiments different dissimilarity measures are represented separately, combinations of these dissimilarity measures may also be used, for example two or more dissimilarity measures may be linearly combined, with the resulting linear combination being used for position determination.

[0069] In the above described embodiment, scalar strain values ​​along the medical device are measured to determine the second distribution, but in other embodiments, multiple strain values ​​can be determined at each location along the medical device. That is, the strain (elongation) can be determined in at least two directions at each location along the medical device. The position determination can then be based on these multi-component strain values ​​and on the first distribution of curvature values. In a further embodiment, the second distribution can also be a distribution of curvature values, whereby the position of the medical device within the tubular structure is determined based on the first and second distributions of curvature values. The second distribution of curvature values ​​can also be determined based on the bi-component or multi-component strain values ​​mentioned above. When the position determination of the medical device within the tubular structure is based on the first and second distributions of curvature values, the curvature values ​​of both distributions are preferably scalar.

[0070] Other variations of the disclosed embodiments can be understood and effected by those skilled in the art from a study of this drawing, this specification, and the appended claims, and from practicing the claimed invention.

[0071] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "eine" do not exclude a plurality.

[0072] A single installation or device may fulfill the functions of several objects recited in the claims. The mere fact that certain measures are recited in different mutually dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0073] The methods performed by one or more facilities or devices, such as determining the position of the instrument in the tubular structure, determining the dissimilarity measure, determining the root value, can be performed by any other number of facilities or devices. These methods and / or the control of the imaging system by the imaging methods and / or the control of the position determination device by the position determination methods can be implemented as program code means of a computer program and / or as dedicated hardware.

[0074] The computer program may be stored / provided together with or as part of other hardware on a suitable medium, such as an optical storage medium or a solid-state medium, but may also be provided in other forms, such as via the Internet or other wired or wireless communication systems.

[0075] Any reference signs in the claims should not be construed as limiting the scope. [Explanation of symbols]

[0076] 1 Imaging system 2 Patient chaise lounge 3 patients 4. Instruments (catheters) 5 Positioning device 6. First Offering Unit 7 Second Offering Unit 8 Positioning Unit 10 Image forming unit 11 Visualization Generation Unit 12 Input Unit 13 Output Unit 31 Blood Vessel Graph 32~35 Curvature profile 38 EKP (Energy Map) 39 Best Route 40~42 OKK (optimal cost curve) 43, 44 OKK with penalty terms 45 Penalty Term K curvature x locations p candidate position t time W root value X Catheter position 101-106 Imaging method steps

Claims

1. A position determination device (5) for determining a position within a tubular structure of an elongated object (4) deforming within the tubular structure, the position determination device (5) comprising: a first providing unit (6) for providing a first distribution of curvature values ​​of the tubular structure at a plurality of first locations along a path in the tubular structure, said first providing unit (6) being configured to provide a first distribution of curvature values ​​for each of a plurality of paths in the tubular structure; a second providing unit (7) for providing a second distribution of strain or curvature values ​​of the object (4) at a plurality of second locations along the object (4), said second providing unit (7) being configured to provide a plurality of second distributions along the object (4) for different points in time, said plurality of second distributions corresponding to a plurality of positions of the object (4) relative to a path of the tubular structure; - it comprises a position determination unit (8) which is configured as follows: - configured for each path and for each time point, respectively, to determine a distribution of dissimilarity values ​​for different candidate positions of the object (4) for the respective path, wherein a dissimilarity measure is applied for various possible candidate positions of the object (4) for the path to a corresponding first distribution and a corresponding second distribution, said dissimilarity measure being configured to result, for each candidate position of the object (4) for the respective path, in a dissimilarity value indicative of the dissimilarity of both distributions at the respective candidate position, wherein a map is provided which is expanded by the different time points and the different candidate positions and which comprises the corresponding dissimilarity values ​​for the different time points and the different candidate positions, - configured to provide a route metric, which for a route through each map ends at one candidate location for the latest time instant and starts at one candidate location for an earlier time instant, results in a route value that is dependent on the dissimilarity values ​​along each route; - for each path, it is configured to determine the route which, using the route measures, determines the route through each map for which the minimum route value is determined, so that optimal routes are found for different paths and thus for different maps, respectively; It is configured to determine the position of the object (4) relative to one of the paths from among those optimum routes detected, the optimum route for which the smallest route value has been determined.

2. the first providing unit (6) is configured to provide, as a first distribution, a distribution of a scalar quantity of curvature values ​​along a path within the tubular structure; 2. The position determining device according to claim 1,

3. the second providing unit (7) is configured to determine the second distribution based on optical signals of a plurality of optical strain sensors arranged along the object (4).

3. A position determining device according to claim 1 or 2, characterized in that

4. the location determination unit (8) is configured to provide a route metric having a component that increases as the sum of dissimilarity values ​​along the respective route increases; A position determining device according to any one of claims 1 to 3, characterized in that

5. The position determination unit (8) - configured to detect optimal routes for different time points, whereby optimal routes with corresponding route values ​​are determined for different time points and different routes, respectively, whereby for a route and a given time point, the detected dissimilarity values ​​for the given time point and for previous time points and for the candidate positions are used to determine the optimal route with corresponding route values, these dissimilarity values ​​being included in said map for each route and its given time point; - adapted to select, at each time point, from the plurality of optimal routes found, the optimal route for which a minimum route value has been determined, with the proviso that, at each time point for said selection, before the optimal route having the minimum route value is selected, the route value is increased for the optimal route for which, at an earlier time point, a minimum route value has not been determined compared with the route values ​​determined for the other optimal routes; - being configured to determine, as the position of the object (4) relative to one of the paths, the position defined by the selected optimal route; A position determining device according to any one of claims 1 to 4, characterized in that

6. The position determination unit (8) is adapted to apply a dissimilarity measure according to the following arrangement: a spatial first gradient distribution of the first distribution is determined, a spatial second gradient distribution of the second distribution is determined, for each location along the object (4), a respective gradient of the second distribution is compared with a respective curvature gradient of the first distribution, whereby each candidate position defines which respective gradient of the second distribution is compared with which respective curvature gradient of the first distribution at each location, whereby for each location and for each candidate position a sub-dissimilarity measure is applied, which sub-dissimilarity measure depends a) on the direction of the gradients relative to each other and / or b) on the magnitude of the gradient of the first distribution and the magnitude of the gradient of the second distribution, whereby a sub-dissimilarity value is determined by applying the sub-dissimilarity measure for each location, The lower dissimilarity values ​​that have been determined for a candidate position are summed to determine a respective dissimilarity value for each candidate position. A position determining device according to any one of claims 1 to 5, characterized in that

7. The position determination unit (8) is adapted to apply a dissimilarity measure according to the following arrangement: a local maximum of the first distribution is determined, a local maximum of the second distribution is determined, the local maxima of the first distribution are assigned to the local maxima of the second distribution in such a way that an assignment is obtained in which the sum of all spatial intervals between the mutually assigned local maxima is minimal, with the proviso that one local maximum of the second distribution is assigned to one local maximum of the first distribution only, and all spatial intervals between the assigned local maxima in the first distribution and the assigned local maxima in the second distribution are added together to obtain a sum; A position determining device according to any one of claims 1 to 6, characterized in that

8. The position determination unit (8) is adapted to apply a dissimilarity measure according to the following arrangement: for each location along the object (4), a respective value of the second distribution is compared with a respective value of the first distribution, with each candidate position defining which respective value of the second distribution is compared with which respective value of the first distribution at each location, with each candidate position applying a sub-dissimilarity measure which results in a sub-dissimilarity value that is zero if a) the respective value of the first distribution is located above a predetermined first threshold, or b) the respective value of the first distribution is located below its first threshold and the respective value of the second distribution is located below a predetermined second threshold, and otherwise has a positive value; The lower dissimilarity values ​​that have been determined for one candidate position are summed to determine a respective dissimilarity value for each candidate position. A position determining device according to any one of claims 1 to 7, characterized in that

9. 1. An imaging system, comprising: - a position determination device (5) for determining the position of an elongate object (4) in a tubular structure according to claim 1; an imaging unit (10) for providing an image of the tubular structure; a visualization generation unit (11) for generating a visualization of the tubular structure based on the provided images and on the determined positions; Having.

10. A method for determining the position within a tubular structure of an elongate object (4) deforming within the tubular structure, the method comprising the steps of: a first providing unit (6) providing a first distribution of curvature values ​​of the tubular structure at a plurality of first locations along a path in the tubular structure, whereby for a plurality of paths in the tubular structure, a respective first distribution of curvature values ​​is provided; a second providing unit (7) providing a second distribution of strain or curvature values ​​of the object (4) at a plurality of second locations along the object (4), wherein a plurality of second distributions are provided along the object (4) for different points in time, said plurality of second distributions corresponding to a plurality of positions of the object (4) relative to a path of the tubular structure; the position determination unit (8) determining, for each path and for each time point, respectively, a distribution of dissimilarity values ​​for different candidate positions of the object (4) for the respective path, wherein a dissimilarity measure is applied for various possible candidate positions of the object (4) for the path to a corresponding first distribution and a corresponding second distribution, said dissimilarity measure being configured to result, for each candidate position of the object (4) for the respective path, in a dissimilarity value indicative of the dissimilarity of both distributions at the respective candidate position, wherein a map is provided which is developed with different time points and different candidate positions and which comprises the corresponding dissimilarity values ​​for the different time points and different candidate positions, a position determination unit (8) providing a route metric, which for a route through each map ends at one candidate location for the latest time instant and starts at one candidate location for an earlier time instant, results in a route value that depends on the dissimilarity values ​​along each route; the position determination unit (8) determines for each path the route for which the minimum route value is determined for the route through the respective map using the route measure, whereby optimal routes are found for different paths and thus for different maps, respectively; a position determination unit (8) determining the position of the object (4) relative to one of the paths from among those optimum routes detected, the optimum route for which the smallest route value has been determined; Contains.

11. 1. An imaging method, the imaging method comprising the steps of: - an imaging unit (10) providing an image of the tubular structure; - determining the position of an elongated object (4) in a tubular structure by means of a position determination device according to claim 1; and - a visualization generation unit generating a visualization of the tubular structure based on the provided images and on the determined positions, Contains.

12. A computer program for determining the position of an elongate medical element, the computer program having program code means adapted to provide instructions to a position determining device (1) according to claim 1 for carrying out the position determining method according to claim 10, when the position determining method according to claim 10 is carried out with the position determining device (1) according to claim 1.

13. An imaging computer program comprising program code means for instructing the imaging system of claim 9 to perform the imaging method of claim 11 when the imaging computer program is run on the imaging system of claim 9.

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