Computer-implemented medical method for user guidance in patient registration

Abstract

The disclosed method encompasses determining guidance data using obtained intra-operation specific property of the patient and / or the situation. The guidance data is used to guide the user in obtaining the registration data. Consequently, improved user guidance in patient registration is provided.

Description

[0001] Brainlab AG

[0002] Attorney’s File: B18880WO

[0003] COMPUTER-IMPLEMENTED MEDICAL METHOD FOR USER GUIDANCE IN PATIENT REGISTRATION

[0004] FIELD OF THE INVENTION

[0005] The present invention relates to a computer-implemented method for user guidance in patient registration, a corresponding data processing apparatus, a patient registration system, a surgical navigation system, computer program and a computer-readable medium.

[0006] TECHNICAL BACKGROUND

[0007] Before performing surgery that uses image guided navigation, a patient has to be registered. Registering the patient comprises a surface matching registration where an intraoperatively acquired point cloud (in cranial use case on the head) is matched with the surface of a pre-operative image set e.g., CT or MRI.

[0008] During the collection of the intraoperatively acquired point cloud, the user guidance in current registration applications is usually limited to a generic guidance of where to acquire points.

[0009] Previous solutions only include a general guidance of where and how many points shall be acquired. There is no situation specific user guidance depending on e.g., the individual patient or the already acquired points. The user needs to consider on his own the additional information given in e.g., the user guide or training material.

[0010] Therefore, it is likely that a less optimal point cloud is acquired by the user and a less then optimal registration match is calculated by the ICP algorithm.

[0011] The present invention has the object of providing improved user guidance in patient registration. The present invention can be used for image-guided surgery such as Cranial Navigation.

[0012] 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.

[0013] EXEMPLARY SHORT DESCRIPTION OF THE INVENTION

[0014] 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.

[0015] The disclosed method encompasses determining guidance data using obtained intraoperation specific property of the patient and / or the situation. The guidance data is used to guide the user in obtaining the registration data. Consequently, improved user guidance in patient registration is provided.

[0016] GENERAL DESCRIPTION OF THE INVENTION

[0017] 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.

[0018] According to another aspect of the invention, a computer-implemented medical method for user guidance in patient registration comprises the following steps. Obtaining at least one intra-operation specific property. Determining at least one guidance data using the at least one obtained intra-operation specific property. Providing intra- operation specific guidance to the user using the at least one determined guidance data, guiding the user in obtaining registration data. Before performing surgery that uses image guided navigation, a patient has to be registered. Registering the patient comprises a surface matching registration where registration data of the patient is matched with pre-operative image data of the patient.

[0019] In the known approaches, only a generic guidance is provided for the user performing patient registration of where to acquire points of the surface patient, namely the registration data. Thus, less optimal registration data is acquired by the user, which leads to a less then optimal patient registration when performing a matching algorithm. Taking into account intra-operation specific properties, in particular of the patient or the situation in the operation room, a more operation-specific and as such an improved guidance can be provided to the user performing patient registration.

[0020] The term “intra-operation specific property”, as used herein, comprises information about the patient and / or the situation in the operation room.

[0021] The term “guidance data”, as used herein, comprises information of how and where registration data should be acquired from the patient. The guidance data forms the basis for an intra-operation specific guidance for the user, supporting the user in patient registration.

[0022] The term “intra-operation specific guidance”, as used herein, comprises a signal to the user, for example a visual signal, an audio signal and / or a vibration signal. The signal provides indication for the user that helps to improve the acquisition of registration data by the user. The user then uses the intra-operation specific guidance to know where and how to acquire registration data from the patient. The intra-operation specific guidance is for example also just referred to as guidance.

[0023] The term “registration data”, as used herein, comprises a plurality of registered points, also referred to as point cloud. The registration data comprises spatial information of each registered point of an actual object (i.e. a patient), in this case the surface of the object, within a space. The registration data is preferably determined by a registration device. The registration device preferably comprises a tracked pointer that is brought into contact with the object to perform contact-based registration. Alternatively, the registration device preferably comprises a non-contact based registration device that is configured to perform non-contact-based registration.

[0024] Consequently, the intra-operation specific properties are taken into account when providing guidance to the user performing patent registration.

[0025] Thus, an improved guidance can be provided to the user performing patient registration.

[0026] In a preferred embodiment, the providing the intra-operation specific guidance comprises prioritizing the at least one guidance data among each other.

[0027] Different intra-operation specific properties might lead to different guidance data. Consequently, the determined guidance data might as well contradict among each other. In other words, the determined guidance might as well lead to contradicting intra- operation specific guidance. Consequently, before providing the intra-operation specific guidance to the user, it has to be decided, which guidance data is actually provided to the user and which guidance data is ignored.

[0028] In other words, providing the intra-operation specific guidance to the user comprises determining for each of the at least one determined guidance data the intra-operation specific guidance, checking the intra-operation specific guidance for contradiction, prioritizing the at least one guidance data so that no contradiction between intra- operation specific guidance remains.

[0029] For example, if first guidance data lead to not to register points on the ear of the patient and second guidance data lead to register points of the ear and the nose, it has to be decided if the specific guidance to the user should reflect registering points on the ear. For example, the first guidance data has a higher priority than the second guidance data, the guidance to the user reflects to register the nose but not the ear.

[0030] Thus, the part of the guidance based on guidance data that contradicts with guidance of other guidance data with a higher priority is ignored. The priority of the guidance data is preferably predetermined based on the impact of the intra-operation specific property, that the guidance data is based on, on the registration data. For example, patient specific properties might have a higher impact on the registration data than situation specific properties. Thus, the guidance, which follows the guidance data of the patient specific properties might have a higher priority than the guidance data of the situation specific properties.

[0031] Thus, an improved guidance can be provided to the user performing patient registration.

[0032] In a preferred embodiment, the at least one intra-operation specific property comprise patient specific properties. The patient specific properties reflect a difference between the patient and image data of the patient.

[0033] In other words, the obtaining the intra-operation specific property comprises determining a relative surface difference between the patient (being the real person in the operation room) and image data of the patient that preferably is used for patient registration.

[0034] The term “image data”, as used herein, comprises images of the patient, that have been acquired pre-operatively and / or intra-operatively. Preferably, the image data is stored in a data storage of a surgical navigation system for computer assisted surgery. Preferably, the image data is acquired from a medical database.

[0035] Consequently, the user is guided in obtaining registration data dependent on possible errors that might be induced to the matching algorithm due to a difference between the patient and image data of the patient.

[0036] Thus, an improved guidance can be provided to the user performing patient registration.

[0037] In a preferred embodiment, the patient specific properties comprise changes to a position and / or orientation of the patient. In other words, it is considered that the patient had another position and / or orientation when acquiring the image data to now in the operation room.

[0038] There are regions of the surface of the patient that are prone to skin shift due to gravity. If those regions are the same in the image data and the registration data, no reduces accuracy of the matching is induced. Due to the change of position and / or orientation of the patient in either the image data or the patient in the operation room setup, where the registration data is obtained, different locations of the image data compared to the registration data have been affected by skin shift, leading to an inherent error in the matching algorithm, reducing the accuracy of the matching.

[0039] Thus, the guidance data indicate regions of the surface of the patient, where no surface points should be acquired due to the described changes.

[0040] Thus, an improved guidance can be provided to the user performing patient registration.

[0041] In a preferred embodiment, the patient specific properties comprise changes to the patient in the image data of the patient.

[0042] In other words, the image data comprises changes to the patient that are not any longer present at the patient in the operation room. Consequently, the changes to the patient in the image data of the patent are not reflected by the registration data, as the reasons for those changes are not present when obtaining the registration data. This inherently leads to an error in the matching algorithm, reducing the accuracy of the matching.

[0043] For example, the changes are initiated by imprints of headphones or pillows and / or cut-offs in the image data.

[0044] Thus, the guidance data indicate regions of the surface of the patient, where no surface points should be acquired due to the described changes.

[0045] Thus, an improved guidance can be provided to the user performing patient registration. In a preferred embodiment, the patient specific properties comprise changes to the patient.

[0046] In other words, the changes to the registered patient are reflected by the registration data but not the image data, as the reasons for those changes are not present when obtaining the image data. This inherently leads to an error in the matching algorithm, reducing the accuracy of the matching.

[0047] For example, the changes are initiated by tapes, tubes, pins of head clamps.

[0048] Thus, the guidance data indicate regions of the surface of the patient, where no surface points should be acquired due to the described changes.

[0049] Thus, an improved guidance can be provided to the user performing patient registration.

[0050] In a preferred embodiment, the patient specific properties are determined by user input and / or an analysis of live visual data of the patient.

[0051] In other words, the information of differences between the patient and the image data needs to be obtained somehow. For example, the user is aware of such differences and provides the difference, or preferably the regions of the surface of the patient. Alternatively, live visual data, in particular live video data, of the patient is used to determine the difference between the patient and the image data.

[0052] Thus, an improved guidance can be provided to the user performing patient registration.

[0053] In a preferred embodiment, the guidance data comprise information of which areas of the patient should not be registered. In other words, the patient specific properties indicate regions of the surface of the patient that inherently lead to errors in the matching algorithm due to the difference between the patient and the image data of the patient.

[0054] Thus, the guidance data indicate regions of the surface of the patient, where no surface points should be acquired by the user due to the described changes.

[0055] Thus, an improved guidance can be provided to the user performing patient registration.

[0056] In a preferred embodiment, the at least one intra-operation specific property comprise situation specific properties, relating to an intra-operation situation.

[0057] Preferably, the intra-operation situation comprises information about the setup in the operation room, the situation of already registered points of the patient and / or a situation of already determined matching solutions, which are based on the already registered points.

[0058] Consequently, the user is guided in which registration device, or in other words instrument, the user should use for which region of the surface of the patient, if further points should be acquired and if yes where.

[0059] Thus, an improved guidance can be provided to the user performing patient registration.

[0060] In a preferred embodiment, the situation specific properties comprise a spatial relation between the patient and a tracking device, which is configured for tracking the patient. The spatial relation comprises a position and / or orientation of the patient and / or the tracking device.

[0061] Preferably, the spatial relation between the patient and a tracking device is used to determine, which region of the surface of the patient can be reached by certain registration devices. There is a plurality of types of registration devices. For example, the registration device type can be a contact-based type or a contact-free type. Due to the nature of the patient not all points of the registration data of the patient might be obtained by a registration device of the same type. For example, if hair is blocking the view of some parts of the patient, instead of a contact-free registration device, a contact-based registration device has to be used.

[0062] Thus, the guidance data indicate regions of the surface of the patient and which type of registration device should be used for acquiring the registration data.

[0063] Thus, an improved guidance can be provided to the user performing patient registration.

[0064] In a preferred embodiment, the situation specific properties are determined by user input and / or an analysis of live visual data of the patient and / or patient location data of the patient and tracking device location data of the tracking device.

[0065] In a preferred embodiment, the guidance data comprise information of which type of registration device should be used for specific areas of the patient.

[0066] Thus, the guidance data indicate regions of the surface of the patient and which type of registration device should be used for acquiring the registration data.

[0067] Thus, an improved guidance can be provided to the user performing patient registration.

[0068] In a preferred embodiment, the situation specific properties comprise an evaluation of already acquired points of the registration data.

[0069] In other words, the previously performed acquiring of registration data is considered for further guidance.

[0070] Thus, an improved guidance can be provided to the user performing patient registration. In a preferred embodiment, the evaluation of the already acquired points comprises an evaluation of an amount of the acquired points.

[0071] In other words, it is considered for guidance if and / or how many points still need to be acquired for the registration data to be considered complete.

[0072] Thus, an improved guidance can be provided to the user performing patient registration.

[0073] In a preferred embodiment, the evaluation of the already acquired points comprises an evaluation of a type of the used registration device.

[0074] In other words, it is considered for guidance with which type of registration device the already acquired points have been acquired. For example, the regions of the surface of the patient are indicated that are especially good to be acquired by the used type of registration device.

[0075] Thus, an improved guidance can be provided to the user performing patient registration.

[0076] In a preferred embodiment, the evaluation of the already acquired points comprises an evaluation of a distribution of the acquired points.

[0077] The distribution preferably comprises a point cluster, an extend and / or a shape of the acquired points.

[0078] Preferably, the point cluster reflects if a point is part of a point cluster. Further preferably, the guidance indicates that from a point cluster no further points should be acquired. Point clusters usually have too many points that do not provide unique information about the surface of the patient and as such are considered to be of lower usefulness to be acquired. Preferably, the extend reflects if a point extends the point cloud. Further preferably, the guidance indicates that from an extend further points should be acquired. Points extending the point cloud are considered useful as they are more likely to provide unique information about the surface of the patient.

[0079] Preferably, the shape reflects the shape of the point cloud. Further preferably, the guidance indicates that from a shape, further points should be acquired as they add uniqueness to the point cloud. Points adding uniqueness to the point cloud are considered useful as they are more likely to provide unique information about the surface of the patient even as points just extending the point cloud.

[0080] Thus, an improved guidance can be provided to the user performing patient registration.

[0081] In a preferred embodiment, the guidance data comprise information of which type of registration device should be used for specific areas of the patient and / or guidance of which areas of the patient should not be registered by the user.

[0082] In a preferred embodiment, the situation specific properties comprise a validation of matching solutions, which are determined by performing a matching algorithm on already acquired points of the registration data and the image data.

[0083] The term “matching algorithm”, as used herein, comprises an algorithm that is configured to match the registration data with the image data set. In other words, the matching algorithm tries to match a location of the registration data and the image data set in the same space. This means that the matching solution provided by the matching algorithm relates to a spatial relation between the image data and the registration data. Preferably, the matching algorithm is a iterative closest point, ICP, algorithm. For the ICP algorithm a start position needs to be guessed and the algorithm reduces the distances of all points of the point cloud to the surface and calculates these matching distances. The matching algorithm tries to reduce the distance to a minimum for finding a good match. However, the matching algorithm also can end in a local minimum, which does not represent the best overall matching result. Even if the matching algorithm finds the global minimum of the lowest distances, it may not be the optimal solution as the image data and registration data are not the same, i.e. the surface has changed. Thus, the matching algorithm is started from changed starting positions to find the overall best matching result, represented by the lowest matching distance.

[0084] The term “matching distance”, as used herein, comprises a single value that reflects the distance of each of the registered points to the image data, in particular to a surface of the object in accordance with the image data. The single value might be an average distance of each of the registered points to the image data. The matching distance therefore relates to the distance between the registered points taken from the surface of the object to the surface of the object according to the image data. The matching distance preferably comprises an average distance of the distances of each of the registered points and the surface of the object according to the image data. Further preferably, the average distance comprises a root mean square.

[0085] The term “matching solution”, as used herein, relates to a correspondence between the image data and the registration data. In other words, the matching solution describes a spatial relation between the image data and the registration data. Preferably, the matching solution is reflected by a transformation matrix between a coordinate system of the image data and a transformation system of the registration data.

[0086] In other words, the matching algorithm is continuously performed. Thus, if additional registration data is acquired, the matching algorithm is performed on all available registration data. This leads to updated matching solutions that is then validated. Preferably, the matching algorithm is performed after a predetermined amount of registration data and / or additional registration data is acquired.

[0087] Preferably, after performing the matching algorithm, surface regions with large matching differences (in other words, above a predetermined threshold) between different similar matching solutions are determined. For those identified surface regions, the guidance date indicates that additional points should be acquired.

[0088] In the following the matching algorithm can be reperformed including the additional acquired points. Thus, an improved guidance can be provided to the user performing patient registration.

[0089] In a preferred embodiment, the guidance data comprise information of which areas of the patient should be registered by the user.

[0090] In a preferred embodiment, the method comprises the following steps: Obtaining registration data. Determining a matching solution using the registration data in a matching algorithm for patient registration. If a stopping criterion is matched, end providing the intra-operation specific guidance to the user and determining the matching solution as a final matching solution. If the stopping criterion is not matched, continue providing the intra-operation specific guidance to the user and jump to the step of obtaining at least one intra-operation specific property.

[0091] In other words, the user is continuously provided with intra-operation specific guidance and the user continuously acquires registration data from the patient using the intra- operation specific guidance.

[0092] Preferably, obtaining the final matching solution comprises determining that no matching solution is found or only bad matching solutions are found. Preferably, obtaining additional registration points comprises acquiring by the user additional registration points. Preferably, the additional registration points are acquired based on the intra-operation specific guidance. Preferably, the stopping criterion is checked in real time.

[0093] In a preferred embodiment, the guidance data comprise information of which areas of the patient should be registered by the user.

[0094] In a preferred embodiment, the matching algorithm comprises determining a matching distance between the image data and the registration data.

[0095] Preferably, the matching distance comprises an average distance of distances of each of the registered points to the surface of the patient according to the image data. average distance comprises a root mean square, RMS, of the distances of each of the registered points and the surface of the patient according to the image data.

[0096] In a preferred embodiment, the matching algorithm comprises an iterative closest point, ICP, algorithm.

[0097] In a preferred embodiment, the ICP algorithm determines a matching distance by iteratively reducing a distance between the registration data and the image data until a minimal matching distance is identified.

[0098] In a preferred embodiment, the image data comprises CT and / or MRT data.

[0099] In a preferred embodiment, the registration data is determined by a registration device.

[0100] In a preferred embodiment, the intra-operation specific guidance comprises visual, audio and / or haptic feedback for the user.

[0101] According to another aspect of the invention, a data processing apparatus comprising means for carrying out the method, as described herein.

[0102] In other words, the invention is directed to at least one computer (for example, a computer), comprising at least one processor (for example, a processor) and at least one memory (for example, a memory), wherein a computer program performing the method steps of the method as described herein is running on the processor or is loaded into the memory, or wherein the at least one computer comprises the computer- readable program storage medium that causes the computer to carry out the method, as described herein.

[0103] According to another aspect of the invention, a patient registration system comprises a registration device, configured to provide registration data of a patient, and the data processing apparatus, as described herein.

[0104] According to another aspect of the invention a surgical navigation system for computer assisted surgery comprises a patient registration system, as described herein. According to another aspect of the invention, a computer program is provided, which, when running on a computer or when loaded onto a computer, causes the computer to perform the method steps of the method, as described herein.

[0105] In other words, the invention is directed to a computer program which, when running on at least one processor (for example, a processor) of at least one computer (for example, a computer) or when loaded into at least one memory (for example, a memory) of at least one computer (for example, a computer), causes the at least one computer to perform the above-described method according to the first aspect. 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, 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 method according to the first aspect. 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 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, for example the internet. The invention according to the second aspect therefore may alternatively or additionally relate to a data stream representative of the aforementioned program.

[0106] According to another aspect of the invention, a computer-readable medium is provided, comprising instructions which, when executed by a computer, cause the computer to carry out the method, as described herein.

[0107] 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. For example, the invention does not comprise a step of positioning a medical implant in order to fasten it to an anatomical structure or a step of fastening the medical implant to the anatomical structure or a step of preparing the anatomical structure for having the medical implant fastened to it. More particularly, the invention does not involve or in particular comprise or encompass any surgical or therapeutic activity. The invention is instead directed as applicable to an image guided navigation system. For this reason alone, no surgical or therapeutic activity and in particular no surgical or therapeutic step is necessitated or implied by carrying out the invention.

[0108] The present invention also relates to the use of the surgical navigation system in computer assisted surgery.

[0109] DEFINITIONS

[0110] In this section, definitions for specific terminology used in this disclosure are offered which also form part of the present disclosure.

[0111] Computer implemented method

[0112] 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.

[0113] 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 "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.

[0114] The invention also relates to a program which, when running on a computer, causes the computer to perform one or more or all of the method steps described herein and / or to a program storage medium on which the program is stored (in particular in a non- transitory form) 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, 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.

[0115] 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.

[0116] Acquiring data

[0117] 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. 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 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.

[0118] Registering

[0119] 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 theater is assigned an image data point of an image (CT, MR, etc.) stored in a navigation system.

[0120] Image registration

[0121] 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.

[0122] Marker

[0123] 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.

[0124] Marker device

[0125] 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.

[0126] 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.

[0127] 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. Marker holder

[0128] 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.

[0129] Pointer

[0130] 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.

[0131] Reference star

[0132] 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.

[0133] Navigation system

[0134] 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.

[0135] 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.

[0136] Surgical navigation system

[0137] 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. Landmarks

[0138] 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.

[0139] Shape representatives

[0140] Shape representatives represent a characteristic aspect of the shape of an anatomical structure. Examples of shape representatives include straight lines, planes and geometric figures. Geometric figures can be one-dimensional such as for example axes or circular arcs, two-dimensional such as for example polygons and circles, or three-dimensional such as for example cuboids, cylinders and spheres. The relative position between the shape representatives can be described in reference systems, for example by co-ordinates or vectors, or can be described by geometric variables such as for example length, angle, area, volume and proportions. The characteristic aspects which are represented by the shape representatives are for example symmetry properties which are represented for example by a plane of symmetry. Another example of a characteristic aspect is the direction of extension of the anatomical structure, which is for example represented by a longitudinal axis. Another example of a characteristic aspect is the cross-sectional shape of an anatomical structure, which is for example represented by an ellipse. Another example of a characteristic aspect is the surface shape of a part of the anatomical structure, which is for example represented by a plane or a hemisphere. For example, the characteristic aspect constitutes an abstraction of the actual shape or an abstraction of a property of the actual shape (such as for example its symmetry properties or longitudinal extension). The shape representative for example represents this abstraction.

[0141] Referencing

[0142] Determining the position is referred to as referencing if it implies informing a navigation system of said position in a reference system of the navigation system.

[0143] Imaging methods

[0144] In the field of medicine, imaging methods (also called imaging modalities and / or medical imaging modalities) are used to generate image data (for example, two- dimensional or three-dimensional image data) of anatomical structures (such as soft tissues, bones, organs, etc.) of the human body. The term "medical imaging methods" is understood to mean (advantageously apparatus-based) imaging methods (for example so-called medical imaging modalities and / or radiological imaging methods) such as for instance computed tomography (CT) and cone beam computed tomography (CBCT, such as volumetric CBCT), x-ray tomography, magnetic resonance tomography (MRT or MRI), conventional x-ray, sonography and / or ultrasound examinations, and positron emission tomography. For example, the medical imaging methods are performed by the analytical devices. Examples for medical imaging modalities applied by medical imaging methods are: X- ray radiography, magnetic resonance imaging, medical ultrasonography or ultrasound, endoscopy, elastography, tactile imaging, thermography, medical photography and nuclear medicine functional imaging techniques as positron emission tomography (PET) and Single-photon emission computed tomography (SPECT), as mentioned by Wikipedia.

[0145] The image data thus generated is also termed “medical imaging data”. Analytical devices for example are used to generate the image data in apparatus-based imaging methods. The imaging methods are for example used for medical diagnostics, to analyse the anatomical body in order to generate images which are described by the image data. The imaging methods are also for example used to detect pathological changes in the human body. However, some of the changes in the anatomical structure, such as the pathological changes in the structures (tissue), may not be detectable and for example may not be visible in the images generated by the imaging methods. A tumour represents an example of a change in an anatomical structure. If the tumour grows, it may then be said to represent an expanded anatomical structure. This expanded anatomical structure may not be detectable; for example, only a part of the expanded anatomical structure may be detectable. Primary / high-grade brain tumours are for example usually visible on MRI scans when contrast agents are used to infiltrate the tumour. MRI scans represent an example of an imaging method. In the case of MRI scans of such brain tumours, the signal enhancement in the MRI images (due to the contrast agents infiltrating the tumour) is considered to represent the solid tumour mass. Thus, the tumour is detectable and for example discernible in the image generated by the imaging method. In addition to these tumours, referred to as "enhancing" tumours, it is thought that approximately 10% of brain tumours are not discernible on a scan and are for example not visible to a user looking at the images generated by the imaging method.

[0146] Mapping

[0147] Mapping describes a transformation (for example, linear transformation) of an element (for example, a pixel or voxel), for example the position of an element, of a first data set in a first coordinate system to an element (for example, a pixel or voxel), for example the position of an element, of a second data set in a second coordinate system (which may have a basis which is different from the basis of the first coordinate system). In one embodiment, the mapping is determined by comparing (for example, matching) the color values (for example grey values) of the respective elements by means of an elastic or rigid fusion algorithm. The mapping is embodied for example by a transformation matrix (such as a matrix defining an affine transformation).

[0148] Medical Workflow

[0149] 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.

[0150] BRIEF DESCRIPTION OF THE DRAWINGS

[0151] 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

[0152] Fig. 1 illustrates the registration data and the image data;

[0153] Fig. 2 illustrates schematically an acquiring of the registration data;

[0154] Fig. 3 is a schematic illustration of the method for user guidance in patient registration; and

[0155] Fig. 4 is a schematic illustration of a surgical navigation system.

[0156] DESCRIPTION OF EMBODIMENTS

[0157] Fig. 1 is a schematical view of the image data Di and the registration data Dr. The registration data Dr relates to a surface of an object, in this case, a head of a patient. In contrast, the image data Di relate to the same object but does not only cover the surface of the object but the whole object. The image data Di preferably comprises magnetic resonance imaging, MRI, data and / or computer tomography, CT, data. The registration data Dr in this case is segmented into different sections. As such the registration data Dr does not only comprise spatial information of the surface of the object, but in particular also section information to which section of the object the respective registration data Dr refers.

[0158] The registration data Dr is provided in a registration data-coordinate system and the image data Di is provided in an image data-coordinate system. The surface matching registration of the invention has the goal to map the registration data Dr onto the surface of the object in accordance with the image data Di.

[0159] Fig. 2 is a schematical view of acquiring the registration data Dr. A user U, which usually is a medical expert, uses a registration device 20 to acquire the registration data Dr from the surface of the object 0. The registration device 20 in this is noncontact based and allows to scan the surface of the object O and provide registration data Dr in form of a point cloud. The registration data Dr comprises a plurality of registered points Dp, which comprise spatial information of each of the registered points Dp within a space. In other words, registration data Dr is acquired in a registration data coordinate system.

[0160] As can be seen from fig. 2, the plurality of registered points Dp form a point cloud in form of the surface of the object O. Thus, the plurality of registered points Dp form a three-dimensional point representation of the surface of the object.

[0161] Fig. 3 is a schematic illustration of the method for user guidance in patient registration.

[0162] In a first step S1 at least one intra-operation specific property P is obtained. In a second step S2, at least one guidance data Dg is determined using the at least one obtained intra-operation specific property P. In a third step, intra-operation specific guidance G is provided to the user U using the at least one determined guidance data, guiding the user U in obtaining registration data Dr. In a fourth step S4, registration data Dp, for example additional registration data, is obtained. In a fifth step S5 a matching solution is determined using the registration data Dp in a matching algorithm for patient registration. In a sixth step S6, if a stopping criterion is matched, the user guidance is ended to provide the intra-operation specific guidance G to the user U and in a seventh step S7 the matching solution is determined as a final matching solution. Alternatively, in the sixth step S6, if the stopping criterion is not matched, it is continued to provide S3 the intra-operation specific guidance G to the user U and it is jumped to the first step S1 of obtaining at least one intra-operation specific property P.

[0163] Fig. 4 is a schematic illustration of a surgical navigation system 1000 comprising a patient registration system 100. The patient registration system 100 comprises an obtaining unit 110, a processing unit 120 and a guidance unit 130.

[0164] The obtaining unit 110 is configured to obtaining at least one intra-operation specific property P. The at least one intra-operation specific property P is then provided to the processing unit 120.

[0165] The processing unit 120 is configured to determine at least one guidance data Dg using the at least one obtained intra-operation specific property P. The at least one guidance data Dg is then provided to the guidance unit 130.

[0166] The guidance unit 130 is configured to provide intra-operation specific guidance G to the user U using the at least one determined guidance data, guiding the user U in obtaining registration data Dr.

Claims

1. Brainlab AGAttorney’s File: B18880WOCLAIMS1. A computer-implemented medical method for user guidance in patient registration, comprising the steps: obtaining (S1 ) at least one intra-operation specific property (P); determining (S2) at least one guidance data (Dg) using the at least one obtained intra-operation specific property (P); providing (S3) intra-operation specific guidance (G) to the user (U) using the at least one determined guidance data, guiding the user (U) in obtaining registration data (Dr).

2. The method of claim 1 , wherein the providing the intra-operation specific guidance (G) comprises prioritizing the at least one guidance data (Dg) among each other.

3. The method of claim 1 or 2, wherein the at least one intra-operation specific property (P) comprise patient specific properties; wherein the patient specific properties reflect a difference between the patient (0) and image data (Di) of the patient (0).

4. The method of claim 3, wherein the patient specific properties comprise changes to a position and / or orientation of the patient (0).

5. The method of any one of the claims 3 or 4, wherein the patient specific properties comprise changes to the patient (0) in the image data (Di) of the patient (0).

6. The method of any one of the claims 3 to 5,wherein the patient specific properties comprise changes to the patient(0).

7. The method of any one of the claims 3 to 6, wherein the patient specific properties are determined by user input and / or an analysis of live visual data of the patient (0).

8. Method of any one of the claims 3 to 7, wherein the guidance data (Dg) comprise information of which areas of the patient (0) should not be registered.

9. The method of any one of the preceding claims, wherein the at least one intra-operation specific property (P) comprise situation specific properties, relating to an intra-operation situation.

10. Method of claim 9, wherein the situation specific properties comprise a spatial relation between the patient (0) and a tracking device, which is configured for tracking the patient (0); wherein the spatial relation comprises a position and / or orientation of the patient (0) and / or the tracking device.

11. The method of claim 10, wherein the situation specific properties are determined by user input and / or an analysis of live visual data of the patient (0) and / or patient location data of the patient (0) and tracking device location data of the tracking device.

12. Method of any one of the claims 10 or 11 , wherein the guidance data (Dg) comprise information of which type of registration device (10) should be used for specific areas of the patient (0).

13. Method of claim 9, wherein the situation specific properties comprise an evaluation of already acquired points (Dp) of the registration data (Dr).

14. Method of claim 13, wherein the evaluation of the already acquired points (Dp) comprises an evaluation of an amount of the acquired points (Dp).

15. Method of any one of the claims 13 or 14, wherein the evaluation of the already acquired points (Dp) comprises an evaluation of a type of the used registration device (10).

16. Method of any one of the claims 13 to 15, wherein the evaluation of the already acquired points (Dp) comprises an evaluation of a distribution of the acquired points (Dp).

17. Method of any one of the claims 13 to 16, wherein the guidance data (Dg) comprise information of which type of registration device (10) should be used for specific areas of the patient (0) and / or guidance of which areas of the patient (0) should not be registered by the user (U).

18. Method of claim 9, wherein the situation specific properties comprise a validation of matching solutions, which are determined by performing a matching algorithm on already acquired points (Dp) of the registration data (Dr) and the image data (Di).

19. Method of claim 18, wherein the guidance data (Dg) comprise information of which areas of the patient (0) should be registered by the user (U).

20. Method of any one of the preceding claims, comprising: obtaining (S4) registration data (Dp); determining (S5) a matching solution using the registration data (Dp) in a matching algorithm for patient registration;if (S6) a stopping criterion is matched, end providing the intra-operation specific guidance (G) to the user (U) and determining (S7) the matching solution as a final matching solution; if (S6) the stopping criterion is not matched, continue providing (S3) the intra-operation specific guidance (G) to the user (U) and jump to the step of obtaining (S1 ) at least one intra-operation specific property (P).21 . The method of any one of the claims 18 to 20, the matching algorithm comprises determining a matching distance between the image data (Di) and the registration data (Dr).

22. The method of claim 21 , wherein the matching algorithm comprises an iterative closest point, ICP, algorithm.

23. The method of claim 22, wherein the ICP algorithm determines a matching distance by iteratively reducing a distance between the registration data (Dr) and the image data (Di) until a minimal matching distance is identified.

24. Method of any one of the preceding claims, wherein the image data (Di) comprises CT and / or MRT data.

25. Method of any one of the preceding claims, wherein the registration data (Dr) is determined by a registration device (10).

26. Method of any one of the preceding claims, wherein the intra-operation specific guidance (G) comprises visual, audio and / or haptic feedback for the user.

27. A data processing apparatus comprising means for carrying out the method of any of the claims 1 -26.

28. A patient registration system comprising a registration device (11), configured to provide registration data (Dr) of a patient (0), and the data processing apparatus of claim 27.

29. A surgical navigation system for computer assisted surgery, the system comprising a patient registration system according to claim 28.

30. A computer program which, when running on a computer or when loaded onto a computer, causes the computer to perform the method steps of the method according to any of the claims 1 -26.

31. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method of any one of the claims 1-26.

Images