Two-dimensional tracking marker

Abstract

The invention relates to a medical tracking marker for being detected and tracked in position during a medical procedure, comprising a substantially planar sub-structure (1) having a front surface (2) and defining a plane (3), and a plurality of features (4, 5, 6) arranged at the front surface (2) and optically different from the front surface (2), wherein the features (5) aligned with the mesh pattern (7) define an optical appearance specific to the tracking marker; and wherein at least one feature (6) is aligned with the mesh pattern (7) and arranged offset from the plane (3). The invention also relates to a set of medical tracking markers comprising a plurality of tracking markers that differ from one another in their optical appearance, and to a computer-implemented medical method of identifying and locating tracking such medical tracking markers.

Description

Technical Field

[0001] The present invention relates to a medical tracking marker configured to be located, detected and tracked during a medical procedure, a corresponding medical tracking marker set comprising a plurality of such tracking markers that differ from one another in their optical appearance, and a computer-implemented method of identifying and locating and tracking such medical tracking markers. Background Art

[0002] Marker tracking systems are commonly used in medical technology to determine and track the positioning of treatment aids, instruments and / or patient body parts. Using the positioning data of the instruments, medical navigation can be performed to assist doctors in treating patients. This enables image-guided surgery, in which doctors can see and check the positioning of their instruments relative to the treatment target (e.g., patient body part) via screen output, even if part of the instrument is no longer visible. This also enables the planning of incisions and / or greatly simplifies the planning of incisions. Data on the patient's anatomical structure can be obtained from previous or intraoperative determination tests using imaging methods such as computed tomography, nuclear spin tomography, X-ray imaging, etc., and can be incorporated into the coordinate system of the operating room and / or instrument tracking system via a registration procedure.

[0003] While some tracking systems, such as many tracking systems that rely on a pair of stereo cameras, are configured to detect spherical tracking markers, where these markers define the marker location at the center of a two-dimensional depiction in the camera image, other tracking systems that may, for example, rely on a monocular camera are configured to determine the spatial location (i.e., spatial position and spatial orientation) of tracking markers and their connected objects by detecting complex geometric structures such as squares, rectangles, triangles, checkerboard patterns, etc. and analyzing how these structures appear in a two-dimensional image obtained via a monocular camera. However, tracking systems that focus on determining marker locations based on detected marker centers have their deficiencies when determining complex geometric structures, and tracking systems with a monocular camera are not suitable for detecting and tracking the spatial location of three-dimensional arrangements of (spherical) tracking markers.

[0004] It can be seen that known tracking systems can only operate in a satisfactory manner if suitable tracking marks are provided.

[0005] It is an object of the present invention to provide a medical tracking marker that can be suitably used in various optical tracking systems, regardless of how these systems process camera images or how many cameras these tracking systems may rely on.

[0006] The present invention can be used in connection with the use of, for example, or any procedures for medical tracking systems, such as those provided by Brainlab AG, which are products of Brainlab AG.

[0007] Various aspects, examples and exemplary steps of the present invention and its embodiments are disclosed below.Different exemplary features of the present invention can be combined according to the present invention when it is technically convenient and feasible. Summary of the invention

[0008] Brief description of invention examples

[0009]

[0013] A brief description of specific features of the invention is given below. This brief description should not be construed as limiting the invention to only the features or combinations of features described in this section.

[0010] The medical tracking marker disclosed herein exhibits a generally flat design with a plurality of optically detectable features disposed on its front surface. Some of these features are arranged relative to each other to define a square grid pattern, which may be the same for a plurality of tracking markers. To distinguish these tracking markers, each tracking marker exhibits a separate optical appearance defined by other optically detectable features, which may also include features defining a grid pattern and are aligned in a specific manner relative to the defined grid pattern. At least one optically detectable feature is disposed offset from a plane including all remaining features, which makes tracking of the tracking marker more robust.

[0011] Summary of the Invention

[0012] In this section, a description of general features of the present invention is given, for example, by referring to possible embodiments of the present invention.

[0013] Generally, the present invention achieves the above objects by providing, in a first aspect, a medical tracking marker configured to be positionally detected and tracked during a medical procedure, the medical tracking marker comprising a substantially planar substructure having a front surface and defining a plane, and a plurality of features disposed at the front surface and optically distinct from the front surface, wherein the plurality of features comprises:

[0014] - a first set of features defining dimensions and orientations of a square grid pattern with equidistant grid spacing in a plane;

[0015] - a second set of features aligned with the grid pattern and defining an optical appearance specific to the tracking mark; and

[0016] -At least one feature aligned to the grid pattern and set to be offset from the plane.

[0017] In other words, the tracking mark comprises a major surface that is substantially flat and exhibits a number of optically detectable features, wherein each of the features serves one or more of the following purposes: A first subset of features is used to define a square grid pattern with equally spaced grid spacing, i.e. a first set of equally spaced grid lines, which extends perpendicularly to a second set of equally spaced grid lines comprising the same number of equally spaced grid lines. A second subset of features is aligned relative to the grid pattern and defines a separate optical appearance of a particular tracking mark, such that multiple tracking marks of the same type, i.e. having the same square grid pattern, can be distinguished. A third subset of optically detectable features, also aligned with the grid pattern, is spaced from a plane containing all other features, such that the spatial orientation of the tracking mark can be reliably determined by a camera even if its line of sight is oriented substantially perpendicular to said plane.

[0018] In a more specific example, the grid pattern of tracking marks includes (n+2) 2 Nodes may be selected, i.e., 4, 9, 16 nodes, etc. Since the effort to determine the location of features and thereby calculate the spatial location of tracking marks increases with the number of features to be detected, 9 nodes has proven to be a favorable number of nodes on which optically detectable features may be arranged.

[0019] In another example, a medical tracking marker may exhibit one or more of the following characteristics:

[0020] - the dimensions of the grid pattern are defined by four features, the four features defining respective corner nodes of the grid pattern;

[0021] - the direction of the grid pattern is defined by the presence or absence of features at corresponding edge nodes between two corner nodes;

[0022] - the grid spacing of the grid pattern is defined by the distance between features disposed at corner nodes and features disposed at edge nodes;

[0023] - At least one feature offset from the plane is arranged at a central node between at least two edge nodes.

[0024] In another example, the specific optical appearance is defined by the size of features arranged at relevant nodes of the grid pattern, the sizes of individual features being different, wherein the sizes are selected from a finite number of predefined sizes, in particular wherein all features of the tracking mark have any one of two predefined sizes.

[0025] As described above, the optical appearance of the tracking mark may be defined not only by the second set of features and their size, but may additionally be defined by the features of the first set of features that already define the square grid pattern.

[0026] In another example, the specific optical appearance is defined by the spatial positioning of individual features relative to associated nodes of the grid pattern, wherein the spatial positioning is selected from a limited number of predefined spatial positionings, in particular wherein all features of the tracking mark have the same size.

[0027] As can be seen from the above examples, the optical appearances that allow different tracking marks of the same type to be distinguished can be based on differences in the size of some features and / or based on differences in the positioning of some features relative to the nodes of the grid pattern. Although it is conceivable that only the second feature set exhibits such deviations in size and / or positioning to define the optical appearance of the tracking mark, it is also conceivable that at least some of the features of the first feature set exhibit deviating sizes to give the tracking mark a specific optical appearance.

[0028] In particular, predefined spatial locations may include:

[0029] - positioning on one of the grid lines adjacent to the node; and / or

[0030] - positioning in one of the grid domains adjacent to the node;

[0031] In particular, wherein the predefined spatial location comprises a predefined distance from the relevant node.

[0032] In other words, the second set of features may be spaced apart from its associated node of the grid pattern and may instead be placed at a distance therefrom and on one of the grid lines intersecting at the node. In an alternative, the features may instead be spaced apart from their associated nodes and instead be spaced within the grid domain, e.g., between grid lines intersecting at the respective nodes. In particular, it is conceivable that the features are spaced apart from their associated nodes by a predefined distance to establish a dedicated relative positioning between the features and their associated nodes. Furthermore, the distance separating the features from their associated nodes may be the same for each feature of the tracking mark.

[0033] In another example, the feature is disk-shaped and / or configured to reflect incident light, and in particular

[0034] - exhibit a high optical contrast towards the front surface of the substructure;

[0035] - Includes retro-reflective coating.

[0036] In other words, a sufficient optical difference needs to be established between the feature and its surroundings, i.e. the front surface of the substructure of the tracking mark. This can be achieved by establishing a high contrast, for example by setting a bright feature on a dark substructure. In addition, the features can have retro-reflective properties, i.e. be configured to reflect incident light back in the same spatial direction. Such features can be shaped as disks to make feature detection easier for the tracking system, which deduce the location of the feature from the center of the feature image received by the tracking camera.

[0037] Additionally or alternatively to the optical properties of the features described above, the features may include light emitting elements, in particular LEDs. In general, any feature may be passive, ie reflect light, or active, ie emit light, or both.

[0038] As for the at least one feature aligned with the grid pattern and further arranged to be offset from the plane including the remaining features, the at least one feature can be arranged in a depression or on a protrusion on the front surface of the substructure of the tracking mark. In this case, the at least one offset feature and all the remaining features can be arranged on the smooth front surface of the substructure.

[0039] The present invention also relates to a medical tracking marker set, comprising a plurality of tracking markers as described above. The tracking markers differ from each other in their optical appearance, which is defined by a second feature set, in particular also by a first feature set, and is specific to the respective tracking marker. Based on the optical appearance unique to each tracking marker, a medical tracking system is able to distinguish between a plurality of tracking markers used for a medical procedure.

[0040] In a second aspect, a computer-implemented medical method is provided for identifying and locating a medical tracking marker during a medical procedure according to one of the above examples. In one example, the method comprises the following steps:

[0041] a) acquiring first feature set data describing the positioning of the first feature set in a plane of an image obtained via an optical camera;

[0042] b) determining grid data based on the first feature set data, the grid data describing the positioning of the grid pattern within the plane of the image;

[0043] c) acquiring second feature set data, the second feature set data describing a positioning of the second feature set in the plane of the image, in particular relative to the first feature set;

[0044] d) determining identification data based on the second feature set data, in particular based on the first feature set data and the second feature set data, the identification data describing the identity of the tracking mark;

[0045] e) acquiring out-of-plane data describing the positioning of at least one feature offset from the plane, in particular relative to the first feature set and / or relative to the second feature set;

[0046] f) determining tracking data based on at least one of the first feature set data, the second feature set data and the out-of-plane data, the tracking data describing the spatial location of the identified tracking mark.

[0047] It is important to note here that the above method steps can be performed in any feasible order. For example, each of the obtaining steps can be performed simultaneously, thereby performing all the determining steps simultaneously.

[0048] In another example, the method may involve using a monocular camera, particularly a monochrome monocular camera, configured to optically detect a plurality of features disposed on a front surface of the substructure.

[0049] In a second aspect, the present invention relates to a computer-implemented medical method for identifying and locating and tracking a medical tracking marker of the above-mentioned type. The present invention may also relate to a computer program comprising instructions, which, when executed by at least one computer, cause the at least one computer to perform a method according to the second aspect. Alternatively or additionally, the present invention may relate to a signal wave (e.g., a physical signal wave generated by technical means, such as an electrical signal wave), such as a digital signal wave, such as an electromagnetic carrier wave carrying information representing a program (e.g., the above-mentioned program), the program for example including a code mechanism suitable for performing any or all steps of the method according to the second aspect. In a certain example, the signal wave is a data carrier signal carrying the above-mentioned computer program. The computer program stored on the disk is a data file, and when the file is read and transmitted, the file becomes a data stream in the form of, for example, a signal (e.g., a physical signal generated by technical means, such as an electrical signal). The signal may be implemented as a signal wave, such as an electromagnetic carrier wave described herein. For example, the signal (e.g., a signal wave) is constructed to be transmitted via a computer network (e.g., a local area network (LAN), a wireless network (WLAN), a wide area network (WAN), a mobile network, such as the Internet). For example, the signal (e.g., a signal wave) is constructed to be transmitted by optical or acoustic data transmission. The invention may alternatively or additionally relate to a data stream representing the above-mentioned program, ie comprising the program.

[0050] In another aspect, the present invention relates to a computer-readable storage medium on which the above-mentioned program is stored. The program storage medium is, for example, a non-transitory program storage medium.

[0051] In another aspect, the present invention relates to at least one computer (eg a computer) comprising at least one processor (eg a processor), wherein the program according to the second aspect is executed by the processor, or at least one computer comprises the above-mentioned computer-readable storage medium.

[0052] definition

[0053] In this section, definitions of specific terms used in the present invention are provided, which also constitute a part of the present invention.

[0054] The method according to the invention is, for example, a computer-implemented method. For example, all or only some of the steps (i.e., less than the total number of steps) of the method according to the invention can be performed by a computer (e.g., at least one computer). An embodiment of a computer-implemented method is a use of a computer-implemented data processing method. An embodiment of a computer-implemented method is a method involving computer operation, such that the computer is operated to perform one, more or all of the steps of the method.

[0055] The computer comprises, for example, at least one processor and, for example, at least one memory, in order to (technically) process data, for example, to process data electronically and / or optically. The processor is, for example, made of a semiconductor substance or composition, for example, at least partially n-type and / or p-type doped semiconductor, for example, at least one of type II, type III, type IV, type V, type VI semiconductor materials, for example (doped) silicon and / or gallium arsenide. The calculation step or determination step is, for example, performed by a computer. The determination step or calculation step is, for example, a step of determining data within the framework of a technical method (for example, within the framework of a program). The computer is, for example, any type of data processing device, for example, an electronic data processing device. The computer can be a device that is generally regarded as a computer, such as a desktop personal computer, a laptop, a netbook, etc., but can also be any programmable device, such as a mobile phone or an embedded processor. The computer can, for example, include a "sub-computer" system (network), in which each sub-computer represents its own computer. The term "computer" includes cloud computers, such as cloud servers. The term "computer" includes server resources. The term "cloud computer" includes a cloud computer system, for example a system including at least one cloud computer, for example including a plurality of operably interconnected cloud computers, such as a server farm. Such a cloud computer is preferably connected to a wide area network such as the World Wide Web (WWW) and is located in a so-called cloud of computers that are all connected to the World Wide Web. Such infrastructure is used for "cloud computing", which describes those computing, software, data access and storage services that do not require the end user to know the physical location and / or configuration of the computer providing a particular service. For example, the term "cloud" is used metaphorically for the Internet (World Wide Web). For example, the cloud provides computing infrastructure as a service (IaaS). A cloud computer can act as a virtual host for an operating system and / or data processing application for performing the method of the present invention. A cloud computer is, for example, provided by Amazon Web Services TM) provided by Elastic Compute Cloud (EC2). The computer, for example, includes an interface to receive or output data and / or perform analog-to-digital conversion. The data, for example, is data representing physical properties and / or generated from technical signals. The technical signal is generated, for example, by a (technical) detection device (for example, a device for detecting a marker) and / or a (technical) analysis device (for example, a device for performing a (medical) imaging method), wherein the technical signal is, for example, an electrical signal or an optical signal. The technical signal, for example, represents data received or output by the computer. The computer is preferably operably coupled to a display device that allows information output by the computer to be displayed to, for example, a user. An example of a display device is a virtual reality device or an augmented reality device (also known as virtual reality glasses or augmented reality glasses), which can act as "goggles" for navigation. A specific example of such augmented reality glasses is Google Glass (Google Glass, a trademark brand of Google, Inc.). The augmented reality device or virtual reality device can be used both to input information into the computer through user interaction and to display information output by the computer. Another example of a display device is a standard computer monitor, for example including a liquid crystal display, which is operatively connected to a computer for receiving display control data from the computer for generating signals for displaying image information content on the display device. A specific embodiment of such a computer monitor is a digital light box. An example of such a digital light box is the product The monitor may also be a handheld portable device such as a smart phone or a personal digital assistant or a digital media player, for example.

[0056] The present invention also relates to a computer program comprising instructions, which, when executed by a computer, cause the computer to perform one or more methods described herein, such as steps of one or more methods; and / or a computer-readable storage medium (such as a non-transitory computer-readable storage medium) storing the above program; and / or a computer comprising the above program storage medium; and / or a signal wave (such as a physical, such as electrical, generated by technical means) carrying information representing a program (such as the above program), such as a digital signal wave, such as an electromagnetic carrier wave, the program for example including a code mechanism suitable for executing any or all of the method steps described herein. In a certain example, the signal wave is a data carrier signal carrying the above computer program. The present invention also relates to a computer, which comprises at least one processor and / or the above computer-readable storage medium and, for example, a memory, wherein the program is executed by a processor.

[0057] In the framework of the present invention, a computer program element may be embodied as hardware and / or software (this includes firmware, resident software, microcode, etc.). In the framework of the present invention, a computer program element may take the form of a computer program product, which may be embodied as a computer-usable, e.g. computer-readable data storage medium, which includes computer-usable, e.g. computer-readable program instructions, the "code" or "computer program" embodied in the data storage medium being used on or in conjunction with an instruction execution system. Such a system may be a computer, which may be a data processing device comprising means for executing a computer program element and / or a program according to the present invention, such as a data processing device comprising a digital processor (central processing unit or CPU) for executing the computer program element, and optionally a data processing device comprising a volatile memory (e.g. random access memory or RAM) for storing data for executing the computer program element and / or generated by executing the computer program element. In the framework of the present invention, a computer-usable, e.g. computer-readable data storage medium may be any data storage medium that may contain, store, communicate, propagate or transmit programs for use on or in conjunction with those instruction execution systems, devices or apparatuses. Computer-usable, for example, computer-readable data storage media can be, for example, but not limited to, electronic, magnetic, optical, electromagnetic, infrared or semiconductor systems, devices or apparatuses, or communication media such as the Internet. Computer-usable or computer-readable data storage media can even be, for example, paper or other suitable media on which the program can be printed, because the program can be captured electronically, for example, by optically scanning the paper or other suitable media, and then compiled, decoded or otherwise processed in an appropriate manner. The data storage medium is preferably a non-volatile data storage medium. The computer program product described herein and any software and / or hardware form various mechanisms for performing the functions of the present invention in the exemplary embodiments. The computer and / or data processing device can, for example, include a guidance information device, which includes a mechanism for outputting guidance information. The guidance information can, for example, be output to the user visually by a visual indication mechanism (e.g., a monitor and / or a light) and / or audibly by an auditory indication mechanism (e.g., a speaker and / or a digital voice output device) and / or tactilely by a tactile indication mechanism (e.g., a vibration element or a vibration element incorporated into an apparatus). For the purposes of this document, a computer is a technical computer, for example comprising technical components such as tangible components, for example mechanical components and / or electronic components. Any device mentioned herein is a technical device and is for example a tangible device.

[0058] The expression "obtaining data" for example includes (within the framework of a computer-implemented method) a scenario in which data is determined by a computer-implemented method or program. Determining data for example includes measuring a physical quantity and transforming the measured value into data, such as digital data, and / or calculating (and for example outputting) the data with the aid of a computer and for example within the framework of the method according to the invention. The "determining" step as described herein for example includes or consists of issuing a command to perform the determination described herein. For example, the step includes or consists of issuing a command to cause a computer (e.g., a remote computer, such as a remote server, such as in the cloud) to perform the determination. Alternatively or additionally, the "determining" step as described herein for example includes or consists of the following steps: receiving result data generated by the determination described herein, for example, receiving result data from a remote computer (e.g., from a remote computer that causes it to perform the determination). The meaning of "obtaining data" also includes, for example, the following scenario: receiving or retrieving data by (e.g., inputting) a computer-implemented method or program, for example, from another program, a previous method step, or a data storage medium, for example, for further processing by a computer-implemented method or program. Generating the data to be acquired can, but need not, be part of the method according to the invention. Therefore, the expression "get data" can also, for example, mean waiting to receive data and / or receiving data. The received data can be input, for example, via an interface. The expression "get data" can also mean that a computer-implemented method or program performs some steps to (actively) receive or retrieve data from a data source such as a data storage medium (e.g., ROM, RAM, database, hard drive, etc.) or via an interface (e.g., from another computer or network). The data obtained by the method or device of the present invention, respectively, can be obtained from a database located in a data storage device, which is operably connected to a computer for data transmission between the database and the computer, such as data transmission from a database to a computer. The computer obtains data for use as input for the step of determining data. The determined data can be output to the same or other databases for storage for subsequent use. The database or the database for implementing the method of the present invention can be located in a network data storage device or a network server (e.g., a cloud data storage device or a cloud server) or a local data storage device (e.g., a mass storage device operably connected to at least one computer performing the method of the present invention). The data can be "ready" by performing an additional step before the acquisition step. According to this additional step, data is generated for acquisition. For example, the data are detected or captured (eg, by an analysis device). Alternatively or additionally, the data are input according to an additional step, such as via an interface. For example, the generated data may be input (eg, into a computer).According to an additional step (which is performed before the acquisition step), the data can also be provided by performing an additional step of storing the data on a data storage medium (such as a ROM, RAM, CD and / or hard drive), so that the data are ready within the framework of the method or program according to the invention. Therefore, the step of "acquiring data" can also involve commanding the device to acquire and / or provide the data to be acquired. In particular, the acquisition step does not involve an invasive step, which represents a substantial physical interference with the body, requiring professional medical measures, and even if the required professional care and measures are taken when performed, the body may be exposed to significant health risks. In particular, the step of acquiring data, such as determining data, does not involve a surgical step, in particular does not involve a step of treating the human or animal body using surgery or therapy. In order to distinguish between different data used by the method according to the invention, the data are represented (i.e. called) "XY data" and the like, and are defined according to the information they describe, and then preferably referred to as "XY information" and the like.

[0059] The function of the marker is to detect the marker in such a way that its spatial location (i.e. its spatial position and / or alignment) can be determined by a marker detection device (e.g. a camera or an ultrasound receiver or an analysis device such as a CT or MRI device). The detection device is, for example, part of a navigation system. The marker can be an active marker. An active marker can, for example, emit electromagnetic radiation and / or waves that can be in the infrared, visible and / or ultraviolet spectral range. However, the marker can also be passive, for example, it can reflect electromagnetic radiation in the infrared, visible and / or ultraviolet spectral range, or it can block X-ray radiation. To this end, a surface with corresponding reflective properties can be provided on the marker or it can be made of metal to block X-ray radiation. The marker can also reflect and / or emit electromagnetic radiation and / or waves in the radio frequency range or in an ultrasonic wavelength. The marker preferably has a spherical and / or ellipsoidal shape and can therefore be referred to as a marker sphere; however, the marker can also exhibit an angular shape, such as a cubic shape.

[0060] The marking device may for example be a reference star or a pointer or a single marker or a plurality of (individual) markers, which are then preferably in a predetermined spatial relationship. The marking device comprises one, two, three or more markers, wherein two or more such markers are in a predetermined spatial relationship. For example, this predetermined spatial relationship is known to the navigation system and is for example stored in a computer of the navigation system.

[0061] In another embodiment, the marking device comprises an optical pattern, for example on a two-dimensional surface. The optical pattern may comprise a plurality of geometric shapes, such as circles, rectangles and / or triangles. The optical pattern may be identified in an image captured by a camera, and the positioning of the marking device relative to the camera may be determined by the size of the pattern in the image, the orientation of the pattern in the image, and the distortion of the pattern in the image. This allows relative positioning to be determined in up to three rotational dimensions and up to three translational dimensions from a single two-dimensional image.

[0062] The positioning of the marking device can be determined, for example, by a medical navigation system. If the marking device is attached to an object, such as a bone or a medical instrument, the positioning of the object can be determined from the positioning of the marking device and the relative positioning between the marking device and the object. Determining this relative positioning is also called registering the marking device and the object. The marking device or object can be tracked, which means that the positioning of the marking device or object is determined two or more times over time.

[0063] A marking holder is understood to mean an attachment device for a single marking, which is used to attach the marking to a holding element of an instrument, a part of a body and / or a reference star, wherein the marking can be attached so that it is stationary and so that it can be advantageously separated. The marking holder can be, for example, rod-shaped and / or cylindrical. A fastening device for the marking device (such as a locking mechanism) can be arranged at the end of the marking holder facing the marking and assist in placing the marking device on the marking holder in a press-fit and / or form-fit manner.

[0064] The present invention also relates to a navigation system for computer-assisted surgery. The navigation system preferably includes the above-mentioned computer for processing the provided data according to the computer-implemented method described in any one of the embodiments described herein. The navigation system preferably includes a detection device for detecting the positioning of detection points representing the main point and the auxiliary point to generate a detection signal and provide the generated detection signal to the computer so that the computer can determine the absolute main point data and the absolute auxiliary point data based on the received detection signal. The detection point is, for example, a point on the surface of the anatomical structure detected by a pointer. In this way, the absolute point data can be provided to the computer. The navigation system also preferably includes a user interface for receiving the calculation results (for example, the positioning of the main plane, the positioning of the auxiliary plane and / or the positioning of the standard plane) from the computer. The user interface provides the received data as information to the user. Examples of user interfaces include display devices such as displays or speakers. The user interface can use any type of indication signal (for example, visual signals, audio signals and / or vibration signals). An example of a display device is an augmented reality device (also called augmented reality glasses), which can be used as so-called "goggles" to navigate. A specific example of such augmented reality glasses is Google Glass (Google Glass, a trademark brand of Google, Inc.). The augmented reality device can both input information into the navigation system's computer through user interaction and display information output by the computer.

[0065] A navigation system, such as a surgical navigation system, is understood to be a system that may include: at least one marking device; a transmitter that emits electromagnetic waves and / or radiation and / or ultrasound; a receiver that receives electromagnetic waves and / or radiation and / or ultrasound; and an electronic data processing device connected to the receiver and / or transmitter, wherein the data processing device (e.g. a computer) for example comprises a processor (CPU) and a working memory, and advantageously comprises an indication device for emitting indication signals (e.g. a visual indication device, such as a monitor, and / or an audio indication device, such as a loudspeaker, and / or a tactile indication device, such as a vibrator) and a permanent data memory, wherein the data processing device processes the navigation data forwarded to it by the receiver and advantageously outputs guidance information to the user via the indication device. The navigation data may be stored in the permanent data memory and, for example, compared with data previously stored in said memory. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The present invention is described below in conjunction with the accompanying drawings, which illustrate the background of the present invention and show specific embodiments of the present invention. However, the scope of the present invention is not limited to the specific features disclosed in the context of the accompanying drawings, in which:

[0067] Figure 1a A first embodiment of a medical tracking marker is shown;

[0068] Figure 1b Shows Figure 1a A stereogram of the tracking markers;

[0069] Figure 2a A second embodiment of a medical tracking marker is shown;

[0070] Figure 2b Shows Figure 2a A stereogram of the tracking markers;

[0071] Figure 3 The basic steps of the method according to the second aspect are shown. DETAILED DESCRIPTION

[0072] Figure 1a A first embodiment of a medical tracking marker according to the first aspect is shown. The top view on the left shows an arrangement of features 4, 5, 6 arranged on a front surface 2 of a substantially planar substructure 1 of the tracking marker. Except for the central feature 6, all features 4, 5 are arranged in the same plane 3 defined by the front surface 2 (i.e. the surface of the substructure 1).

[0073] like Figure 1a As shown in the side and cross-sectional views to the right, the central feature 6 is disposed in a recess 10 formed in the center of the substructure 1 and is therefore offset from the plane 3 that includes all the remaining features 4 , 5 .

[0074] The square grid pattern 7 is defined by four features 4 located at each corner of the substructure 1, with another feature 4 disposed at the top center of the substructure 1 defining not only the distance or grid spacing d, but also the "top" direction of the tracking marks.

[0075] The grid pattern has a total of nine nodes 8 , at which the grid lines of the grid pattern 7 intersect and also mark four square grid domains 9 .

[0076] In order to establish an individual optical appearance of a specific tracking mark, additional features 5 are arranged at the edge nodes 8 between the corner nodes 8. For each of the features 5, there are three possibilities for arrangement, namely on one of the three grid lines intersecting the corresponding edge node 8. In the example shown, the feature 5 and its associated edge node 8 are separated by a predefined distance s, which is equal for each feature 5. With a total of three features 5 that can be arranged at three different locations, the example shown allows providing 27 individual tracking marks that the tracking system is able to distinguish from each other.

[0077] Figure 2a Shown with Figure 1aAnother example of a medical tracking marker is shown, which differs in that the specific optical appearance is not established by spacing some features 5 from their associated nodes 8 in a specific direction, but by arranging the features 5 with different sizes compared to the remaining features 4, 6. Although all features 4, 5, 6 are located in the center of their corresponding nodes 8, the features 5 located at the lower left and upper right corners of the substructure 1 exhibit larger sizes than the remaining features 4, 6. In this regard, it should be mentioned that the features 5, among other features 4, define the dimensions and directions of the grid pattern 7 (see Figure 1a ), but also provides an optical appearance specific to one of multiple tracking marks.

[0078] In addition, unlike combining Figure 1a As explained in the example of FIG. 4 , one of the features 4 is set to be centered at its associated node 8 to define a “top” direction, and a “bottom” direction is defined by Figure 2a The missing feature definition at the bottom center of the substructure 1 of the example shown.

[0079] Figure 1b and Figure 2b They are shown respectively Figure 1a and Figure 2a A stereogram of the example shown in .

Claims

1. A medical tracking marker for location detection and tracking during a medical procedure, comprising a substantially planar substructure (1) having a front surface (2) and defining a plane (3), and a plurality of features (4, 5, 6) disposed at the front surface (2) and optically distinct from the front surface (2), wherein the plurality of features (4, 5, 6) comprises: - a first set of features (4) defining dimensions and orientations of a square grid pattern (7) with equidistant grid spacing within said plane (3); - a second set of features (5) aligned with said grid pattern (7) and defining an optical appearance specific to said tracking mark; as well as - at least one feature (6) aligned with the grid pattern (7) and arranged offset from the plane (3).

2. The medical tracking marker of claim 1, wherein the grid pattern (7) comprises (n+2) 2 nodes (8), in particular nine nodes (8).

3. The medical tracking marker according to any one of claims 1 and 2, wherein - the dimensions of the grid pattern (7) are defined by four features (4), the four features (4) defining respective corner nodes (8) of the grid pattern (7); - said direction of said grid pattern (7) is defined by the presence or absence of a feature (4) at a corresponding edge node (8) between two corner nodes (8); - the grid spacing of the grid pattern (7) is defined by the distance (d) between the features (4) arranged at the corner nodes (8) and the features (4) arranged at the edge nodes (8); The at least one feature (6) offset from the plane (3) is arranged at a central node (8) between at least two edge nodes (8).

4. The medical tracking marker according to any one of claims 1 to 3, wherein the specific optical appearance is defined by the size of the features (4, 5, 6) arranged at the relevant nodes (8) of the grid pattern (7), the size being different for individual features (4, 5, 6), wherein the size is selected from a limited number of predefined sizes, in particular wherein all features (4, 5, 6) of the tracking marker have either of two predefined sizes.

5. The medical tracking marker of claim 4, wherein the optical appearance is defined by the sizes of features of the first feature set (4) and the sizes of features of the second feature set (5).

6. A medical tracking marker according to any one of claims 1 to 3, wherein the specific optical appearance is defined by the spatial positioning of individual features (5) relative to associated nodes (8) of the grid pattern (7), wherein the spatial positioning is selected from a limited number of predefined spatial positionings, in particular wherein all features (4, 5, 6) of the tracking marker have the same size.

7. The medical tracking marker of claim 6, wherein the predefined spatial location comprises: - positioning on one of said grid lines (7) adjacent to said node (8); and / or - positioning in one of the grid domains (9) adjacent to said node (8); In particular, said predefined spatial location comprises a predefined distance (s) from said relevant node (8).

8. A medical tracking marker according to any one of claims 1 to 7, wherein the feature (4, 5, 6) is disc-shaped and configured to reflect incident light, and in particular - exhibits a high optical contrast towards the front surface (2) of the substructure (1); - Includes retro-reflective coating.

9. The medical tracking marker according to any one of claims 1 to 8, wherein each of the plurality of features (4, 5, 6) comprises a light emitting element, in particular an LED.

10. The medical tracking marker according to any one of claims 1 to 9, wherein the at least one feature (6) offset from the plane (3) is provided in a recess (10) or on a protrusion of the front surface (2) of the substructure (1).

11. A medical tracking mark set comprising a plurality of tracking marks according to any one of claims 1 to 10, wherein the tracking marks differ from each other in an optical appearance, the optical appearance being defined by the second feature set (5), in particular by the first feature set (4) and by the second feature set (5), and being specific to the respective tracking mark.

12. A computer-implemented medical method for identifying and locating a medical tracking marker according to any one of claims 1 to 10 during a medical procedure, the method comprising the steps of: a) acquiring first feature set data (S11), the first feature set data describing the positioning of the first feature set (4) in a plane of an image obtained via an optical camera; b) determining grid data (S12) based on the first feature set data, the grid data describing the positioning of the grid pattern (7) within the plane of the image; c) acquiring second feature set data (S13), the second feature set data describing the positioning of the second feature set (5) within the plane of the image, in particular relative to the first feature set (4); d) determining identification data (S14) based on the second feature set data, in particular based on the first feature set data and the second feature set data, the identification data describing the identity of the tracking mark; e) acquiring out-of-plane data (S15), the out-of-plane data describing the positioning of the at least one feature (6) offset from the plane (3), in particular relative to the first feature set (4) and / or relative to the second feature set (5); f) determining tracking data based on at least one of the first feature set data, the second feature set data and the out-of-plane data (S16), the tracking data describing the spatial location of the identified tracking mark.

13. The method according to claim 12 involves the use of a single camera, in particular a monochrome single camera, which is configured to optically detect and distinguish the multiple features (4, 5, 6) of the front surface (2) of the substructure (1).

Images