Head clamp system

Abstract

The present invention relates to a trackable head clamp system comprising a head clamp (1) including a first leg portion (2) and a second leg portion (3) which adjustably connect to each other so as to receive a patient's head between them, wherein at least one of the first leg portion (2) and the second leg portion (3) features a plurality of identical tracking marker attachment sections (4) adapted to detachably connect to a respective medical tracking marker (5) in a spatially fixed manner. The present invention further relates to corresponding methods of tracking the spatial position of such head clamp (1).

Description

[0001] HEAD CLAMP SYSTEM

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a head clamp system which is adapted to be spatially determined and tracked over time via a medical tracking system. The invention further relates to a corresponding medical method of tracking the spatial position of such head clamp system, a corresponding computer-implemented method of tracking the spatial position of such head clamp system, a corresponding computer program, a computer- readable storage medium storing such a program and a computer executing the program, as well as a medical system comprising an electronic data storage device and the aforementioned computer.

[0004] TECHNICAL BACKGROUND

[0005] During medical interventions performed on the head and / or the neck of a patient, it is necessary to immobilize these anatomical body parts. For this purpose, head clamps are used which are typically designed as U-shaped structures that can be manually adjusted so as to receive a patient’s skull and apply thereon a holding force from opposite directions, which is sufficient to safely stabilize the patient’s head and / or neck during the medical intervention. For computer assisted neurosurgery, it is also important that the spatial position of the patient’s head and / or neck is consistently known to a medical navigation system in order for it to calculate and show the correct spatial relative position between the patient’s anatomy and medical instruments and devices. Thus, head clamps are often fitted with tracking markers to be spatially detected and tracked by a medical tracking system. On this basis a medical navigation system can calculate the spatial position of the patient’s anatomy. Such trackable head clamps however do have their drawbacks which need to be taken into account during the intervention. For example, a persisting line-of-sight between the one or more cameras of the medical tracking system and the head clamp’s tracking marker needs to be maintained for a continuous supervision of the head clamp’s position, which may impede or even prevent a smooth medical workflow. Further, a change of the tracking technology, which may be desirable in some cases, requires the tracking markers of one tracking technology to be replaced by tracking markers of another tracking technology, followed by a re-registration of the patient’s anatomy with respect to the head clamp.

[0006] The present invention has the object of providing a trackable head clamp system and corresponding methods, which facilitate tracking the spatial position of a head clamp along with the patient’s anatomy.

[0007] The present invention can be used for any computer assisted medical procedures performed on a patient’s head and / or neck in connection with a medical tracking system such as Kick® and Curve®, both products of Brainlab AG.

[0008] Aspects of the present invention, examples and exemplary steps and their embodiments are disclosed in the following. Different exemplary features of the invention can be combined in accordance with the invention wherever technically expedient and feasible.

[0009] EXEMPLARY SHORT DESCRIPTION OF THE INVENTION

[0010] In the following, a short description of the specific features of the present invention is given which shall not be understood to limit the invention only to the features or a combination of the features described in this section.

[0011] The present invention relates to a trackable head clamp system comprising a head clamp including a first leg portion and a second leg portion which adjustably connect to each other so as to receive a patient's head between them, wherein at least one of the first leg portion and the second leg portion features a plurality of identical tracking marker attachment sections adapted to detachably connect to a respective medical tracking marker in a spatially fixed manner.

[0012] The present invention further relates to corresponding methods of tracking the spatial position of such head clamp.

[0013] GENERAL DESCRIPTION OF THE INVENTION

[0014] In this section, a description of the general features of the present invention is given for example by referring to possible embodiments of the invention.

[0015] In general, the invention reaches the aforementioned object by providing, in a first aspect, a trackable head clamp system comprising a head clamp including a first leg portion and a second leg portion which adjustably connect to each other so as to receive a patient's head between them, wherein at least one of the first leg portion and the second leg portion features a plurality of identical tracking marker attachment sections adapted to detachably connect to a respective medical tracking marker in a spatially fixed manner.

[0016] In other words, the concept according to the present invention is to equip a head clamp with a plurality of identical tracking marker attachment sections, each of which allows for releasably attaching a medical tracking marker to the head clamp. Any or both of the head clamp’s legs may therefore be fitted with a plurality of such tracking marker attachment sections, so that any of these components may be fitted with one or more tracking markers at different sections thereof. Firstly, the concept described herein allows for attaching various tracking markers to the head clamp or even to one or both leg portions thereof, wherein the tracking markers may even pertain to different tracking technologies. Secondly, this concept allows for selecting, from a plurality of possible attachment sections, one or more attachment sections which are considered best for being fitted with a tracking marker during a specific procedure.

[0017] In an example, the trackable head clamp system further comprises a plurality of said medical tracking markers adapted to be spatially recognized by a medical tracking system, wherein each of said tracking markers is adapted to detachably connect to a respective one of said tracking marker attachment sections in a spatially fixed manner. The trackable head clamp system may include a plurality of medical tracking markers one or more of which can be attached to a desired one of the plurality of attachment sections. The plurality of tracking markers may not only distinguish from each other by at least one feature adapted to be recognized by a medical tracking system, for example in their optical appearance, but these tracking markers may also pertain to different tracking technologies, for example an optical, an electromagnetic or an ultrasound tracking technology. In this regard, it is important to note that each one of the plurality of tracking markers may be adapted to connect to any of the plurality of tracking marker attachment sections so as to maximize flexibility in fitting the head clamp with tracking markers.

[0018] In an example of the head clamp system, the tracking marker attachment sections are adapted to detachably connect to respective tracking markers independently from each other. In other words, any of the tracking marker attachment sections may connect to or may be disconnected from a tracking marker irrespective of whether or not other attachment sections connect to a tracking marker. Therefore, the attachment sections may be independently fitted with or released from a corresponding tracking marker. In still other words, at least one of the first and second leg position may comprise at least two discrete tracking marker attachment sections.

[0019] In a further example, at least one of said tracking marker attachment sections and at least one of said tracking markers are adapted to connect to each other with a surgical drape extending between the tracking marker attachment section and said tracking marker. In this example, the coupling between the attachment section and the tracking marker is configured to allow for rigidly attaching the tracking marker to the attachment section irrespective of whether or not a drape extends between the attachment section and the tracking marker. Such configuration is advantageous in medical interventions for which the head clamp is spatially tracked before and after it is covered with a surgical drape. Of course, the surgical drape then extends between the head clamp and the distant tracking system. While, before the head clamp is covered, a tracking marker may directly connect to the attachment section, this or another attachment section may connect to a tracking marker with the surgical drape extending between the attachment section and the tracking marker, when the patient’s head along with the head clamp is covered.

[0020] In a further example, at least one of said tracking marker attachment sections is adapted to connect to a respective tracking marker in at least two spatial positions of the tracking marker relative to the tracking marker attachment section. Such configuration increases flexibility in the use of the head clamp even more as there is no need in attaching a tracking marker to a corresponding attachment section in a specific relative position. Rather, the one or more tracking markers may be attached to one or more corresponding attachment sections in an unspecific position. For example, an attachment section of this type may be configured as a clamping rail which may receive, at any position along its extension, a correspondingly shaped tracking marker. Basically, such attachment section may comprise one or more movable chucks adapted to grasp and hold a tracking marker in place, irrespective of the specific relative position between the tracking marker and the attachment section. This may either be accomplished by establishing a friction-fit or a form-fit between the tracking marker and the attachment section.

[0021] In another embodiment, at least one of said tracking marker attachment sections comprises at least one spring-loaded, at least one elastically deformable and / or at least one tapering gripping section which is adapted to clamp in a respective tracking marker, for example via a friction-fit. In such case, at least the portion of a tracking marker to be clamped in by the attachment section may have a sheet-like and / or flat shape. As will be described further below, there is no need for connecting the tracking markers to the respective attachment sections at a unique position. Rather, any attachment may be considered sufficient as long as the tracking marker is held firmly, i.e. invariants in place by the attachment section.

[0022] In another example, one of the at least one tracking marker attachment section and the at least one tracking marker comprises a permanent magnet or an electromagnet, wherein the other of the at least one tracking marker attachment section and the at least one tracking marker comprises

[0023] - a permanent magnet or an electromagnet; or

[0024] - a ferromagnetic element.

[0025] As to the plurality of medical tracking markers, these tracking markers may pertain to different tracking technologies, particularly

[0026] - an optical tracking technology, specifically based on infrared light and / or involving the use of planar tracking markers, which are also referred to as 2D-tracking markers

[0027] - an electromagnetic tracking technology, specifically wherein said tracking markers include electromagnetic-sensors or electromagnetic-emitters; and / or

[0028] - an ultrasound tracking technology, specifically wherein said tracking markers include ultrasound-sensors or ultrasound-emitters.

[0029] A plurality of tracking markers may be attached to the head clamp so as to increase tracking accuracy and / or to implement redundancy in tracking the head clamp. Further, at least one of said medical tracking markers may be adapted to define six spatial degrees of freedom. In other words, one of such tracking marker would be sufficient to fully determine the spatial position (including three rotational orientations and three translational locations in three dimensional space) of the head clamp.

[0030] Additional advantages of the specific configurations of the head clamp explained above will become more apparent below when referring to the concept of how the inventive head clamp system is utilized.

[0031] In a second aspect, the invention is directed to a medical method, a computer- implemented medical method and a computer program comprising instructions which, when the program is executed by at least one computer, causes the at least one computer to carry out such method.

[0032] A computer-implemented method of tracking the spatial position of a head clamp according to the present invention may include the following steps: first tracking marker position data is acquired, describing a relative position between a patient’s head and a first tracking marker connecting to a first tracking marker attachment section of the head clamp; first tracking data is determined based on the first tracking marker position data, describing a spatial position of the patient’s head received between the first leg portion and the second leg portion of the head clamp; relative tracking marker position data is determined, describing the relative position between a second tracking marker and the first tracking marker; second tracking data is determined based on the relative tracking marker position data, describing the spatial position of the patient’s head.

[0033] For example, a computer of a medical navigation system may receive data as to the relative position between the patient’s head anatomy and a first tracking marker as described herein. This data may be acquired in the context of a registration process, which is to spatially align medical image data with the actual anatomy of the patient. Based on this data, the patient’s head, i.e. the patient's anatomy can be spatially tracked and positionally aligned with a corresponding image dataset of the patient. However, events may occur which impede tracking the patient's head via the first tracking marker. For example, a change in the medical setup results in an interruption of the line-of-sight between the first tracking marker and the medical tracking system. In such case, the concept described herein allows for attaching a second tracking marker to the head clamp whereupon the computer is able to receive or calculate data as to the relative position between the first tracking marker and the second tracking marker, both of which are spatially recognized by the medical tracking system.

[0034] Once the relative position between the first tracking marker and the second tracking marker is known, the patient’s head, i.e. the patient's anatomy can be spatially tracked based on the detected position of the second tracking marker even without the position of the first tracking marker being known or recognized by the medical tracking system afterwards.

[0035] In a medical method according to the present invention, the spatial position of a head clamp is tracked by:

[0036] - providing a trackable head clamp system described herein;

[0037] - connecting a first tracking marker to a first tracking marker attachment section in a spatially fixed manner;

[0038] - determining a relative position between the first tracking marker and the patient’s head;

[0039] - tracking the spatial position of a patient’s head received between the first leg portion and the second leg portion of the head clamp over time based on the determined relative position between the first tracking marker and the patient’s head;

[0040] - connecting a second tracking marker to a second tracking marker attachment section in a spatially fixed manner, particularly wherein the second tracking marker distinguishes from the first tracking marker by at least one feature adapted to be recognized by a medical tracking system;

[0041] - determining the relative position between the second tracking marker and the first tracking marker;

[0042] - tracking the spatial position of a patient’s head over time based on the determined relative position between the second tracking marker and the first tracking marker and the determined relative position between the first tracking marker and the patient’s head.

[0043] As was already described further above, the step of determining the relative position between the second tracking marker and the first tracking marker may directly precede a change of a medical setup involving the use of the trackable head clamp system and a medical tracking system, particularly wherein

[0044] - the arrangement of the medical tracking system relative to the head clamp system is changed; - the patient’s head along with the first leg portion and the second leg portion of the head clamp is covered with a surgical drape; and / or

[0045] - the change of the setup eliminates or impedes a line of sight between the medical tracking system and the first tracking marker.

[0046] The invention may alternatively or additionally relate to a (physical, for example electrical, for example technically generated) signal wave, for example a digital signal wave, such as an electromagnetic carrier wave carrying information which represents the program, for example the aforementioned program, which for example comprises code means which are adapted to perform any or all of the steps of the aforementioned method. The signal wave is in one example a data carrier signal carrying the aforementioned computer program. A computer program stored on a disc is a data file, and when the file is read out and transmitted it becomes a data stream for example in the form of a (physical, for example electrical, for example technically generated) signal. The signal can be implemented as the signal wave, for example as the electromagnetic carrier wave which is described herein. For example, the signal, for example the signal wave is constituted to be transmitted via a computer network, for example LAN, WLAN, WAN, mobile network, for example the internet. For example, the signal, for example the signal wave, is constituted to be transmitted by optic or acoustic data transmission. The invention according to the second aspect therefore may alternatively or additionally relate to a data stream representative of the aforementioned program, i.e. comprising the program.

[0047] In a third aspect, the invention is directed to a computer-readable storage medium on which the program according to the second aspect is stored. The program storage medium is for example non-transitory.

[0048] In a fourth aspect, the invention is directed to at least one computer (for example, a computer), comprising at least one processor (for example, a processor), wherein the program according to the second aspect is executed by the processor, or wherein the at least one computer comprises the computer-readable storage medium according to the third aspect. In a fifth aspect, the invention is directed to a for example non-transitory computer- readable program storage medium storing a program for causing the computer according to the fourth aspect to execute the data processing steps of the method according to the second aspect.

[0049] For example, the disclosed method is not a method for treatment of the human or animal body by surgery or therapy. For example, the invention does not involve or in particular comprise or encompass an invasive step which would represent a substantial physical interference with the body requiring professional medical expertise to be carried out and entailing a substantial health risk even when carried out with the required professional care and expertise.

[0050] DEFINITIONS

[0051] In this section, definitions for specific terminology used in this disclosure are offered which also form part of the present disclosure.

[0052] Computer-implemented method

[0053] The method in accordance with the invention is for example a computer-implemented method. For example, all the steps or merely some of the steps (i.e. less than the total number of steps) of the method in accordance with the invention can be executed by a computer (for example, at least one computer). An embodiment of the computer implemented method is a use of the computer for performing a data processing method. An embodiment of the computer implemented method is a method concerning the operation of the computer such that the computer is operated to perform one, more or all steps of the method.

[0054] The computer for example comprises at least one processor and for example at least one memory in order to (technically) process the data, for example electronically and / or optically. The processor being for example made of a substance or composition which is a semiconductor, for example at least partly n- and / or p-doped semiconductor, for example at least one of II-, III-, IV-, V-, Vl-sem iconductor material, for example (doped) silicon and / or gallium arsenide. The calculating or determining steps described are for example performed by a computer. Determining steps or calculating steps are for example steps of determining data within the framework of the technical method, for example within the framework of a program. A computer is for example any kind of data processing device, for example electronic data processing device. A computer can be a device which is generally thought of as such, for example desktop PCs, notebooks, netbooks, etc., but can also be any programmable apparatus, such as for example a mobile phone or an embedded processor. A computer can for example comprise a system (network) of "sub-computers", wherein each sub-computer represents a computer in its own right. The term "computer" includes a cloud computer, for example a cloud server. The term computer includes a server resource. The term "cloud computer" includes a cloud computer system which for example comprises a system of at least one cloud computer and for example a plurality of operatively 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 located in a so-called cloud of computers which are all connected to the world wide web. Such an infrastructure is used for "cloud computing", which describes computation, software, data access and storage services which do not require the end user to know the physical location and / or configuration of the computer delivering a specific service. For example, the term "cloud" is used in this respect as a metaphor for the Internet (world wide web). For example, the cloud provides computing infrastructure as a service (laaS). The cloud computer can function as a virtual host for an operating system and / or data processing application which is used to execute the method of the invention. The cloud computer is for example an elastic compute cloud (EC2) as provided by Amazon Web Services™. A computer for example comprises interfaces in order to receive or output data and / or perform an analogue-to-digital conversion. The data are for example data which represent physical properties and / or which are generated from technical signals. The technical signals are for example generated by means of (technical) detection devices (such as for example devices for detecting marker devices) and / or (technical) analytical devices (such as for example devices for performing (medical) imaging methods), wherein the technical signals are for example electrical or optical signals. The technical signals for example represent the data received or outputted by the computer. The computer is preferably operatively coupled to a display device which allows information outputted by the computer to be displayed, for example to a user. One example of a display device is a virtual reality device or an augmented reality device (also referred to as virtual reality glasses or augmented reality glasses) which can be used as "goggles" for navigating. A specific example of such augmented reality glasses is Google Glass (a trademark of Google, Inc.). An augmented reality device or a virtual reality device can be used both to input information into the computer by user interaction and to display information outputted by the computer. Another example of a display device would be a standard computer monitor comprising for example a liquid crystal display operatively coupled to the computer for receiving display control data from the computer for generating signals used to display image information content on the display device. A specific embodiment of such a computer monitor is a digital lightbox. An example of such a digital lightbox is Buzz®, a product of Brainlab AG. The monitor may also be the monitor of a portable, for example handheld, device such as a smart phone or personal digital assistant or digital media player.

[0055] The invention also relates to a computer program comprising instructions which, when on the program is executed by a computer, cause the computer to carry out the method or methods, for example, the steps of the method or methods, described herein and / or to a computer-readable storage medium (for example, a non-transitory computer- readable storage medium) on which the program is stored and / or to a computer comprising said program storage medium and / or to a (physical, for example electrical, for example technically generated) signal wave, for example a digital signal wave, such as an electromagnetic carrier wave carrying information which represents the program, for example the aforementioned program, which for example comprises code means which are adapted to perform any or all of the method steps described herein. The signal wave is in one example a data carrier signal carrying the aforementioned computer program. The invention also relates to a computer comprising at least one processor and / or the aforementioned computer-readable storage medium and for example a memory, wherein the program is executed by the processor.

[0056] Within the framework of the invention, computer program elements can be embodied by hardware and / or software (this includes firmware, resident software, micro-code, etc.). Within the framework of the invention, computer program elements can take the form of a computer program product which can be embodied by a computer-usable, for example computer-readable data storage medium comprising computer-usable, for example computer-readable program instructions, "code" or a "computer program" embodied in said data storage medium for use on or in connection with the instructionexecuting system. Such a system can be a computer; a computer can be a data processing device comprising means for executing the computer program elements and / or the program in accordance with the invention, for example a data processing device comprising a digital processor (central processing unit or CPU) which executes the computer program elements, and optionally a volatile memory (for example a random access memory or RAM) for storing data used for and / or produced by executing the computer program elements. Within the framework of the present invention, a computer-usable, for example computer-readable data storage medium can be any data storage medium which can include, store, communicate, propagate or transport the program for use on or in connection with the instruction-executing system, apparatus or device. The computer-usable, for example computer-readable data storage medium can for example be, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, apparatus or device or a medium of propagation such as for example the Internet. The computer-usable or computer-readable data storage medium could even for example be paper or another suitable medium onto which the program is printed, since the program could be electronically captured, for example by optically scanning the paper or other suitable medium, and then compiled, interpreted or otherwise processed in a suitable manner. The data storage medium is preferably a non-volatile data storage medium. The computer program product and any software and / or hardware described here form the various means for performing the functions of the invention in the example embodiments. The computer and / or data processing device can for example include a guidance information device which includes means for outputting guidance information. The guidance information can be outputted, for example to a user, visually by a visual indicating means (for example, a monitor and / or a lamp) and / or acoustically by an acoustic indicating means (for example, a loudspeaker and / or a digital speech output device) and / or tactilely by a tactile indicating means (for example, a vibrating element or a vibration element incorporated into an instrument). For the purpose of this document, a computer is a technical computer which for example comprises technical, for example tangible components, for example mechanical and / or electronic components. Any device mentioned as such in this document is a technical and for example tangible device.

[0057] Acquiring data

[0058] The expression "acquiring data" for example encompasses (within the framework of a computer implemented method) the scenario in which the data are determined by the computer implemented method or program. Determining data for example encompasses measuring physical quantities and transforming the measured values into data, for example digital data, and / or computing (and e.g. outputting) the data by means of a computer and for example within the framework of the method in accordance with the invention. A step of “determining” as described herein for example comprises or consists of issuing a command to perform the determination described herein. For example, the step comprises or consists of issuing a command to cause a computer, for example a remote computer, for example a remote server, for example in the cloud, to perform the determination. Alternatively or additionally, a step of “determination” as described herein for example comprises or consists of receiving the data resulting from the determination described herein, for example receiving the resulting data from the remote computer, for example from that remote computer which has been caused to perform the determination. The meaning of "acquiring data" also for example encompasses the scenario in which the data are received or retrieved by (e.g. input to) the 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 the computer implemented method or program. Generation of the data to be acquired may but need not be part of the method in accordance with the invention. The expression "acquiring data" can therefore also for example mean waiting to receive data and / or receiving the data. The received data can for example be inputted via an interface. The expression "acquiring data" can also mean that the computer implemented method or program performs steps in order to (actively) receive or retrieve the data from a data source, for instance a data storage medium (such as for example a ROM, RAM, database, hard drive, etc.), or via the interface (for instance, from another computer or a network). The data acquired by the disclosed method or device, respectively, may be acquired from a database located in a data storage device which is operably to a computer for data transfer between the database and the computer, for example from the database to the computer. The computer acquires the data for use as an input for steps of determining data. The determined data can be output again to the same or another database to be stored for later use. The database or database used for implementing the disclosed method can be located on network data storage device or a network server (for example, a cloud data storage device or a cloud server) or a local data storage device (such as a mass storage device operably connected to at least one computer executing the disclosed method). The data can be made "ready for use" by performing an additional step before the acquiring step. In accordance with this additional step, the data are generated in order to be acquired. The data are for example detected or captured (for example by an analytical device). Alternatively or additionally, the data are inputted in accordance with the additional step, for instance via interfaces. The data generated can for example be inputted (for instance into the computer). In accordance with the additional step (which precedes the acquiring step), the data can also be provided by performing the additional step of storing the data in a data storage medium (such as for example a ROM, RAM, CD and / or hard drive), such that they are ready for use within the framework of the method or program in accordance with the invention. The step of "acquiring data" can therefore also involve commanding a device to obtain and / or provide the data to be acquired. In particular, the acquiring step does not involve an invasive step which would represent a substantial physical interference with the body, requiring professional medical expertise to be carried out and entailing a substantial health risk even when carried out with the required professional care and expertise. In particular, the step of acquiring data, for example determining data, does not involve a surgical step and in particular does not involve a step of treating a human or animal body using surgery or therapy. In order to distinguish the different data used by the present method, the data are denoted (i.e. referred to) as "XY data" and the like and are defined in terms of the information which they describe, which is then preferably referred to as "XY information" and the like.

[0059] Registering

[0060] The n-dimensional image of a body is registered when the spatial location of each point of an actual object within a space, for example a body part in an operating theatre, is assigned an image data point of an image (CT, MR, etc.) stored in a navigation system.

[0061] Image registration

[0062] Image registration is the process of transforming different sets of data into one coordinate system. The data can be multiple photographs and / or data from different sensors, different times or different viewpoints. It is used in computer vision, medical imaging and in compiling and analysing images and data from satellites. Registration is necessary in order to be able to compare or integrate the data obtained from these different measurements.

[0063] Marker

[0064] It is the function of a marker to be detected by a marker detection device (for example, a camera or an ultrasound receiver or analytical devices such as CT or MRI devices) in such a way that its spatial position (i.e. its spatial location and / or alignment) can be ascertained. The detection device is for example part of a navigation system. The markers can be active markers. An active marker can for example emit electromagnetic radiation and / or waves which can be in the infrared, visible and / or ultraviolet spectral range. A marker can also however be passive, i.e. can for example reflect electromagnetic radiation in the infrared, visible and / or ultraviolet spectral range or can block X-ray radiation. To this end, the marker can be provided with a surface which has corresponding reflective properties or can be made of metal in order to block the X-ray radiation. It is also possible for a marker to reflect and / or emit electromagnetic radiation and / or waves in the radio frequency range or at ultrasound wavelengths. A marker preferably has a spherical and / or spheroid shape and can therefore be referred to as a marker sphere; markers can however also exhibit a cornered, for example cubic, shape.

[0065] Marker device

[0066] A marker device can 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. A marker device comprises one, two, three or more markers, wherein two or more such markers are in a predetermined spatial relationship. This predetermined spatial relationship is for example known to a navigation system and is for example stored in a computer of the navigation system.

[0067] In another embodiment, a marker device comprises an optical pattern, for example on a two-dimensional surface. The optical pattern might comprise a plurality of geometric shapes like circles, rectangles and / or triangles. The optical pattern can be identified in an image captured by a camera, and the position of the marker device relative to the camera can be determined from 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 determining the relative position in up to three rotational dimensions and up to three translational dimensions from a single two-dimensional image.

[0068] The position of a marker device can be ascertained, for example by a medical navigation system. If the marker device is attached to an object, such as a bone or a medical instrument, the position of the object can be determined from the position of the marker device and the relative position between the marker device and the object. Determining this relative position is also referred to as registering the marker device and the object. The marker device or the object can be tracked, which means that the position of the marker device or the object is ascertained twice or more over time.

[0069] Marker holder

[0070] A marker holder is understood to mean an attaching device for an individual marker which serves to attach the marker to an instrument, a part of the body and / or a holding element of a reference star, wherein it can be attached such that it is stationary and advantageously such that it can be detached. A marker holder can for example be rodshaped and / or cylindrical. A fastening device (such as for instance a latching mechanism) for the marker device can be provided at the end of the marker holder facing the marker and assists in placing the marker device on the marker holder in a force fit and / or positive fit.

[0071] Pointer

[0072] A pointer is a rod which comprises one or more - advantageously, two - markers fastened to it and which can be used to measure off individual co-ordinates, for example spatial co-ordinates (i.e. three-dimensional co-ordinates), on a part of the body, wherein a user guides the pointer (for example, a part of the pointer which has a defined and advantageously fixed position with respect to the at least one marker attached to the pointer) to the position corresponding to the co-ordinates, such that the position of the pointer can be determined by using a surgical navigation system to detect the marker on the pointer. The relative location between the markers of the pointer and the part of the pointer used to measure off co-ordinates (for example, the tip of the pointer) is for example known. The surgical navigation system then enables the location (of the three-dimensional co-ordinates) to be assigned to a predetermined body structure, wherein the assignment can be made automatically or by user intervention. Reference star

[0073] A "reference star" refers to a device with a number of markers, advantageously three markers, attached to it, wherein the markers are (for example detachably) attached to the reference star such that they are stationary, thus providing a known (and advantageously fixed) position of the markers relative to each other. The position of the markers relative to each other can be individually different for each reference star used within the framework of a surgical navigation method, in order to enable a surgical navigation system to identify the corresponding reference star on the basis of the position of its markers relative to each other. It is therefore also then possible for the objects (for example, instruments and / or parts of a body) to which the reference star is attached to be identified and / or differentiated accordingly. In a surgical navigation method, the reference star serves to attach a plurality of markers to an object (for example, a bone or a medical instrument) in order to be able to detect the position of the object (i.e. its spatial location and / or alignment). Such a reference star for example features a way of being attached to the object (for example, a clamp and / or a thread) and / or a holding element which ensures a distance between the markers and the object (for example in order to assist the visibility of the markers to a marker detection device) and / or marker holders which are mechanically connected to the holding element and which the markers can be attached to.

[0074] Navigation system

[0075] The present invention is also directed to a navigation system for computer-assisted surgery. This navigation system preferably comprises the aforementioned computer for processing the data provided in accordance with the computer implemented method as described in any one of the embodiments described herein. The navigation system preferably comprises a detection device for detecting the position of detection points which represent the main points and auxiliary points, in order to generate detection signals and to supply the generated detection signals to the computer, such that the computer can determine the absolute main point data and absolute auxiliary point data on the basis of the detection signals received. A detection point is for example a point on the surface of the anatomical structure which is detected, for example by a pointer. In this way, the absolute point data can be provided to the computer. The navigation system also preferably comprises a user interface for receiving the calculation results from the computer (for example, the position of the main plane, the position of the auxiliary plane and / or the position of the standard plane). The user interface provides the received data to the user as information. Examples of a user interface include a display device such as a monitor, or a loudspeaker. The user interface can use any kind of indication signal (for example a visual signal, an audio signal and / or a vibration signal). One example of a display device is an augmented reality device (also referred to as augmented reality glasses) which can be used as so-called "goggles" for navigating. A specific example of such augmented reality glasses is Google Glass (a trademark of Google, Inc.). An augmented reality device can be used both to input information into the computer of the navigation system by user interaction and to display information outputted by the computer.

[0076] The invention also relates to a navigation system for computer-assisted surgery, comprising: a computer for processing the absolute point data and the relative point data; a detection device for detecting the position of the main and auxiliary points in order to generate the absolute point data and to supply the absolute point data to the computer; a data interface for receiving the relative point data and for supplying the relative point data to the computer; and a user interface for receiving data from the computer in order to provide information to the user, wherein the received data are generated by the computer on the basis of the results of the processing performed by the computer.

[0077] Surgical navigation system

[0078] A navigation system, such as a surgical navigation system, is understood to mean a system which can comprise: at least one marker device; a transmitter which emits electromagnetic waves and / or radiation and / or ultrasound waves; a receiver which receives electromagnetic waves and / or radiation and / or ultrasound waves; and an electronic data processing device which is connected to the receiver and / or the transmitter, wherein the data processing device (for example, a computer) for example comprises a processor (CPU) and a working memory and advantageously an indicating device for issuing an indication signal (for example, a visual indicating device such as a monitor and / or an audio indicating device such as a loudspeaker and / or a tactile indicating device such as a vibrator) and a permanent data memory, wherein the data processing device processes navigation data forwarded to it by the receiver and can advantageously output guidance information to a user via the indicating device. The navigation data can be stored in the permanent data memory and for example compared with data stored in said memory beforehand.

[0079] Landmarks

[0080] A landmark is a defined element of an anatomical body part which is always identical or recurs with a high degree of similarity in the same anatomical body part of multiple patients. Typical landmarks are for example the epicondyles of a femoral bone or the tips of the transverse processes and / or dorsal process of a vertebra. The points (main points or auxiliary points) can represent such landmarks. A landmark which lies on (for example on the surface of) a characteristic anatomical structure of the body part can also represent said structure. The landmark can represent the anatomical structure as a whole or only a point or part of it. A landmark can also for example lie on the anatomical structure, which is for example a prominent structure. An example of such an anatomical structure is the posterior aspect of the iliac crest. Another example of a landmark is one defined by the rim of the acetabulum, for instance by the centre of said rim. In another example, a landmark represents the bottom or deepest point of an acetabulum, which is derived from a multitude of detection points. Thus, one landmark can for example represent a multitude of detection points. As mentioned above, a landmark can represent an anatomical characteristic which is defined on the basis of a characteristic structure of the body part. Additionally, a landmark can also represent an anatomical characteristic defined by a relative movement of two body parts, such as the rotational centre of the femur when moved relative to the acetabulum. Fixed (relative) position

[0081] A fixed position, which is also referred to as fixed relative position, in this document means that two objects which are in a fixed position have a relative position which does not change unless this change is explicitly and intentionally initiated. A fixed position is in particular given if a force or torque above a predetermined threshold has to be applied in order to change the position. This threshold might be 10 N or 10 Nm. In particular, the position of a sensor device remains fixed relative to a target while the target is registered or two targets are moved relative to each other. A fixed position can for example be achieved by rigidly attaching one object to another. The spatial location, which is a part of the position, can in particular be described just by a distance (between two objects) or just by the direction of a vector (which links two objects). The alignment, which is another part of the position, can in particular be described by just the relative angle of orientation (between the two objects).

[0082] Medical Workflow

[0083] A medical workflow comprises a plurality of workflow steps performed during a medical treatment and / or a medical diagnosis. The workflow steps are typically, but not necessarily performed in a predetermined order. Each workflow step for example means a particular task, which might be a single action or a set of actions. Examples of workflow steps are capturing a medical image, positioning a patient, attaching a marker, performing a resection, moving a joint, placing an implant and the like.

[0084] BRIEF DESCRIPTION OF THE DRAWINGS

[0085] In the following, the invention is described with reference to the appended figures which give background explanations and represent specific embodiments of the invention. The scope of the invention is however not limited to the specific features disclosed in the context of the figures, wherein Fig. 1 shows a head clamp system according to the first aspect;

[0086] Fig. 2 illustrates the basic steps of the method according to the second aspect;

[0087] Fig. 3 illustrates the basic steps of the computer-implemented method according to the second aspect.

[0088] DESCRIPTION OF EMBODIMENTS

[0089] Fig. 1 shows a trackable head clamp system according to the first aspect that includes a head clamp 1 the structure of which is of a conventional design. The head clamp 1 includes a first leg portion 2 which connects to a second leg portion 3 via a translatory guide. The translatory guide allows for a relative translational motion between the first leg portion 2 and the second leg portion 3 so as to increasing the opening width of the head clamp 1. This allows for a patient’s head to be received between the first leg portion 2 and the second leg portion 3, wherein the distance between the first leg portion 2 and the second leg portion 3 is reduced again such that the patient’s head is engaged, from opposite directions, by pins disposed at the free ends of both of the leg portions 2, 3. Once the relative position of the first and second leg portions 2, 3 is fixed and a predefined clamping force is established via a force applicator (not indicated in Fig. 1 ), the patient’s head is ready for being registered with respect to a corresponding image dataset. Such registration process includes determining the relative position between the patient’s head and at least one of the tracking markers 5 which are rigidly attached to the head clamp 1 via respective attachment sections 4.

[0090] As shown in Fig. 1 , both of the first leg portion 2 and the second leg portion 3 feature identical attachment sections 4, each of which allows for attaching a respective tracking marker 5 to the head clamp. In this regard it should be noted that, for the sake of simplification, any parts or components of the head clamp 1 which directly connect to one of the first leg portion 2 and the second leg portion 3 is considered a part of the respective leg portion. In the example shown in Fig. 1 , each one of the plurality of medical tracking markers 5 is configured as planar, sheet-like shaped tracking marker which features a specific pattern of multiple circular features recognizable to an optical tracking system. The tracking markers shown in Fig. 1 distinguish from each other in the size and the specific arrangement of these recognizable features, such that a medical navigation system is abled to distinguish between these tracking markers. The attachment sections 4 are configured as jaw chucks adapted to releasably grip any of the sheet-like shaped tracking markers 5. In this context, it should be noted that the tracking markers 5 can be easily repositioned at the head clamp 1 or even be replaced by tracking markers pertaining to another tracking technology such as electromagnetic tracking or ultrasound tracking.

[0091] Figures 2 and 3 show flow-diagrams including the basic steps of the computer- implemented method and the medical method according to the second aspect, respectively, for tracking the spatial position of the head clamp according to the first aspect.

Claims

CLAIMS1. Trackable head clamp system comprising a head clamp (1 ) including a first leg portion (2) and a second leg portion (3) which adjustably connect to each other so as to receive a patient's head between them, wherein at least one of the first leg portion (2) and the second leg portion (3) features a plurality of identical tracking marker attachment sections (4) adapted to detachably connect to a respective medical tracking marker (5) in a spatially fixed manner.

2. Trackable head clamp system according to claim 1 , further comprising a plurality of said medical tracking markers (5) adapted to be spatially recognized by a medical tracking system, wherein each of said tracking markers (5) is adapted to detachably connect to a respective one of said tracking marker attachment sections (4) in a spatially fixed manner.

3. Trackable head clamp system according to any one of claims 1 and 2, wherein said tracking marker attachment sections (4) are adapted to detachably connect to respective tracking markers (5) independently from each other.

4. Trackable head clamp system according to any one of claims 1 to 3, wherein at least one of said tracking marker attachment sections (4) and at least one of said tracking markers (5) are adapted to connect to each other with a surgical drape extending between the tracking marker attachment section (4) and said tracking marker (5).

5. Trackable head clamp system according to any one of claims 1 to 4, wherein at least one of said tracking marker attachment sections (4) is adapted to connect to a respective tracking marker (5) in at least two spatial positions of the tracking marker (5) relative to the tracking marker attachment section (4).

6. Trackable head clamp system according to claim 5, wherein at least one of said tracking marker attachment sections (4) comprises jaw chucks adapted to clamp one of said medical tracking markers (5).

7. Trackable head clamp system according to any one of claims 1 to 5, wherein at least one of said tracking marker attachment sections (4) comprises at least one springloaded, elastically deformable and / or tapering gripping section adapted to clamp in a respective tracking marker (5), particularly via a friction fit.

8. Trackable head clamp system according to any one of claims 1 to 5, wherein one of the at least one tracking marker attachment section (4) and the at least one tracking marker (5) comprises a permanent magnet or an electromagnet, and wherein the other of the at least one tracking marker attachment section (4) and the at least one tracking marker (5) comprises a permanent magnet or an electromagnet; or a ferromagnetic element.

9. Trackable head clamp system according to any one of claims 1 to 8, wherein the plurality of said medical tracking markers (5) includes tracking markers underlying different tracking technologies, particularly an optical tracking technology, specifically based on infrared (IR) light and / or involving the use of planar (2D) tracking markers; an electromagnetic (EM) tracking technology, specifically wherein said tracking markers include EM-sensors or EM-emitters; and / or an ultrasound (US) tracking technology, specifically wherein said tracking markers include US-sensors or US-emitters.

10. Trackable head clamp system according to any one of claims 1 to 9, wherein at least one of said medical tracking markers (5) is adapted to define 6 spatial degrees of freedom.11 . A computer-implemented method of tracking the spatial position of a head clamp (1 ), the method comprising the following steps: first tracking marker position data is acquired (S11 ), describing a relative position between a patient’s head and a first tracking marker (5) connecting to a first tracking marker attachment section (4) of the head clamp (1 ); first tracking data is determined (S12) based on the first tracking marker position data, describing a spatial position of the patient’s head received between the first leg portion (2) and the second leg portion (3) of the head clamp (1 ); relative tracking marker position data is determined (S13), describing the relative position between a second tracking marker (5) and the first tracking marker (5); second tracking data is determined (S14) based on the relative tracking marker position data, describing the spatial position of the patient’s head.

12. A medical method of tracking the spatial position of a head clamp, the method comprising the following steps: providing a trackable head clamp system according to any one of claims 1 to 10; connecting a first tracking marker (5) to a first tracking marker attachment section (4) in a spatially fixed manner; determining a relative position between the first tracking marker (5) and the patient’s head; tracking the spatial position of a patient’s head received between the first leg portion (2) and the second leg portion (3) of the head clamp (1 ) over time based on the determined relative position between the first tracking marker (5) and the patient’s head; connecting a second tracking marker (5) to a second tracking marker attachment section (4) in a spatially fixed manner, particularly wherein the second tracking marker (5) distinguishes from the first tracking marker (5) by at least one feature adapted to be recognized by a medical tracking system; determining the relative position between the second tracking marker (5) and the first tracking marker (5);tracking the spatial position of a patient’s head over time based on the determined relative position between the second tracking marker (5) and the first tracking marker (5) and the determined relative position between the first tracking marker (5) and the patient’s head.

13. The method of claim 11 or of claim 12, wherein the step of determining the relative position between the second tracking marker (5) and the first tracking marker (5) directly precedes a change of a medical setup involving the use of the trackable head clamp system and a medical tracking system, particularly wherein the arrangement of the medical tracking system relative to the head clamp (1 ) system is changed; the patient’s head along with the first leg portion (2) and the second leg portion (3) of the head clamp (1 ) is covered with a surgical drape; and / or the change of the setup eliminates or impedes a line of sight between the medical tracking system and the first tracking marker (5).

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