System for magnetic tracking using reusable components

Abstract

The disclosed electronics unit comprises re-usable electronic components for magnetic tracking which are non-sterile, but can be encapsulated in a sterile, disposable hull. The hull can be a medical instrument or a separate entity which is mechanically connectable to a medical instrument. The electronics unit has a housing with an elongated shape along in a longitudinal direction.

Description

[0001] SYSTEM FOR MAGNETIC TRACKING USING REUSABLE COMPONENTS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a re-usable, non-sterile electronics unit (1 ) for use in a system for magnetic tracking in a medical environment and systems comprising the re-usable, non-sterile electronics unit.

[0004] TECHNICAL BACKGROUND

[0005] In the medical context, several approaches are known for tracking the position of a medical instrument. In this context, the term position means the location in up to three spatial dimensions and / or the orientation in up to three rotational dimensions.

[0006] One approach involves magnetic tracking in which sensors attached to the medical instrument detect a magnetic field generated by a field generator. The sensor output is typically transferred to a computing unit which calculates the position of the medical instrument, for example in a reference system of the field generator.

[0007] Some approaches use wireless transmission of the sensor data to the computing unit. However, medical instruments comprising wireless components are not suitable for steam sterilization since the wireless components might be damaged. On the other hand, the wireless components are too expensive for many disposable instruments. The present invention thus aims at re-using electronic components in magnetic tracking.

[0008] The present invention can for example be used for Cranial EM Navigation and ENT EM Navigation, both being products of Brainlab AG. 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 disclosed electronics unit comprises re-usable electronic components which are non-sterile, but can be encapsulated in a sterile, disposable hull, which is also referred to as receiving element. The hull can be a medical instrument or a separate entity which is mechanically connectable to a medical instrument.

[0012] GENERAL DESCRIPTION OF THE INVENTION

[0013] 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.

[0014] In general, the invention reaches the aforementioned object by providing a re-usable, non-sterile electronics unit. The electronics unit comprises a housing and at least one magnetometer sensor. A magnetometer sensor is a sensor that can detect the local strength of a magnetic field, which is generated by a field generator, at a sensor position. Any suitable kind of magnetometer sensor can be used. Each of the at least one magnetometer sensors is located at a predetermined position inside the electronics unit.

[0015] The electronics unit further comprises a sensor interface unit configured to process sensor data received from a magnetometer sensor. Depending on the implementation, the magnetometer sensor whose output data is processed can be an internal magnetometer sensor comprised in the electronics unit and / or an external magnetometer sensor external to the electronics unit. Processing for example involves digitizing an analog output from the magnetometer sensor. However, a magnetometer sensor could already provide a digital signal to the sensor interface unit. In this case, the sensor interface unit for example acts as micro controller that communicates with the magnetometer sensor and forwards the sensor data to the computing unit via a wireless communication module described below. Processing for example involves adding information identifying the magnetometer sensor which has measured the strength of the magnetic field in association with the measured strength. Alternatively, processing involves adding information on the position of the magnetometer sensor which has measured the strength of the magnetic field in association with the strength.

[0016] The electronics unit further comprises a wireless communication module configured to transmit the sensor data after processing by the sensor interface unit to a computing unit.

[0017] Still further, the electronics unit comprises a plurality of electric contacts reaching to the outside of the housing. Via the electric contacts, the electronics unit can be connected to other components. Reaching to the outside of the housing means that the electric contacts can be electrically contacted from the outside of the housing.

[0018] Yet further, the housing has an elongated shape along a longitudinal axis. This means that the extent of the housing in a longitudinal direction, which is a direction of the longitudinal axis or parallel thereto, is longer than any extent along another axis which is perpendicular to the longitudinal axis. However, the extent along the longitudinal axis is not necessarily the longest possible extent of the housing. The longitudinal axis of the housing for example connects opposite surfaces of the housing.

[0019] In one implementation, the housing has the shape of a cylinder. In this case, the longitudinal axis can be the central axis of the cylinder. The shape of the housing can deviate from the shape of an ideal cylinder, for example if one or both of the end surfaces are not flat, but bulged outwards, for example in the shape of a hemisphere. The cylinder can have an outer diameter of for example 2 cm, 1 ,5 cm, 1 cm or less than 1 cm. In this context, “elongated” for example means that the extent of the housing along the longitudinal axis is at least 2, 3, 4, 5, 6, 7, 8, 9 or 10 times the extent along any other axis perpendicular to the longitudinal axis.

[0020] In one example, the longitudinal axis of the housing is an axis which is parallel to an edge of the housing.

[0021] The advantage of such an electronics unit is that it can be inserted into a sterile receiving element, be removed from the receiving element after use and be re-used after sterilization of the receiving element or with a new receiving element. In addition, the electronics unit can be used in combination with multiple kinds of receiving element. The receiving element can for example be a sterile case or a sterile medical instrument as explained below. In this document, the terms “sterile receiving element” and “receiving element” are used synonymously.

[0022] In one embodiment, the housing is rotationally asymmetric along at least a part of its longitudinal extent. This allows the electronics unit to be accommodated in the sterile receiving element with a predetermined rotational alignment about the longitudinal axis (or an axis parallel thereto).

[0023] In one implementation, the housing has a cylindrical main body with a flat side along at least a part of its longitudinal extent. The housing is thus basically cylindrical as described above, but has a flat portion. In a cross-sectional plane perpendicular to the longitudinal axis, the lateral surface of the housing is no pure circle, but a circle which is cut along a chord. The part where the flat side and the round part of the housing meet can be the edge of the housing to which the longitudinal axis is parallel.

[0024] The flat portion might extend along less than the maximum extent of the lateral surface of the cylinder. The flat portion is preferably at the end of the lateral surface which is inserted into the receiving element first. In another implementation, the housing has a cylindrical main body with a protrusion in a direction perpendicular to the longitudinal axis of the housing. The protrusion, which can also be referred to as a nose, can have any shape as long as it prevents a rotation of the housing relative to the receiving element about the longitudinal axis (or an axis parallel thereto).

[0025] In yet another implementation, the housing has a polygonal cross-section. This allows an insertion of the electronics unit into the housing in certain rotational alignments only. The polygonal cross-section is for example non-regular, such that there is only a single rotational alignment about the longitudinal axis in which the electronics unit can be inserted into the receiving element.

[0026] It is understood that the receiving element has a shape that is inverse to the shape of the housing such that the electronics unit cannot rotate within the receiving element about the longitudinal axis, or an axis parallel thereto.

[0027] In one embodiment, a first longitudinal end of the housing is rounded. This rounded end can have a hemispherical shape as discussed above regarding a cylindrical housing. However, the first longitudinal end of the housing of any shape can be rounded, including a housing with a polygonal cross-section. The rounded end improves mating of the electronics unit with the receiving element and can aid when inserting the electronics unit into the receiving element.

[0028] In one embodiment, the housing has a light emitting surface at a second longitudinal end. The second longitudinal end is for example the opposite end to the first longitudinal end at which the housing is rounded. Via the light emitting surface, the electronics unit can provide information to the outside.

[0029] The light emitting surface can include at least a part of, or all of, the end surface of the housing at the second longitudinal end. But the light emitting surface can be located in a range between 1 % and 10 % of the longitudinal length of the housing away from the second longitudinal end. This range defines the position of the light emitting surface, but not the size of the light emitting surface along the longitudinal axis. The light emitting surface may be a circumferential ring of the housing, for example surrounding the longitudinal axis completely about 360 degrees. The light emitting surface can be a combination of the above.

[0030] In one implementation, the light emitting surface is made of a translucent material and the electronics unit comprises a light emitting element inside the housing. The light emitting surface thus guides the light emitted by the light emitting element to the outside of the housing. In another implementation, the light emitting element is embedded within the housing itself and the light emitting surface is part or all of the surface of the light emitting element.

[0031] In one embodiment, the electronics unit is configured to indicate its status via the light emitting surface. The electronics unit can indicate the status for example via the color of the emitted light, a blinking pattern of the emitted light, the brightness of the emitted light or a combination thereof.

[0032] The status can for example comprise a positive operating status indicating that the electronics unit is operable. That the electronics unit is operable can include one or more of that it is compatible with the receiving element into which it is inserted and that it is correctly positioned in the receiving element. The positive operating status can for example be indicated by green light emitted from the light emitting surface.

[0033] The status can further include a fault status of the electronics unit. The fault status may include one or more of the status of a battery of the electronics unit and feedback information from the computing unit to which the electronics unit shall transmit the sensor data. The feedback information may for example indicate whether or not the electronics unit was used more than a predetermined number of times. The fault status may be indicated by light of magenta color emitted from the light emitting surface. The status can further include a pairing mode status between the electronics unit and another device, for example the computing unit. The pairing mode status can for example be indicated by blue light emitted from the light emitting surface.

[0034] The status can further be a loading status of a battery of the electronics unit. The loading status for example indicates that the electronics unit is connected to a dock described later and that the battery is being charged or that the battery is charged to a predetermined level.

[0035] In one embodiment, the electronics unit further comprises a visual marking on the front face of a longitudinal end of the housing. Said front face preferably is the front face of the housing which is not inserted into the receiving element first. In the terminology used above, said front face with the marking is the one at the opposite end of the housing, in the longitudinal direction, to the first longitudinal end that is rounded. With the marking, correct insertion of the electronics unit into the receiving element can be verified by a visual check. The marking can be a colored marking in a color different from the color of the housing around the marking, a structural marking, like a protrusion or a recess, or a combination thereof.

[0036] In one embodiment, the housing can comprise an opening at one longitudinal end and a cap to close the opening. The longitudinal end with the opening is for example the longitudinal end opposite to the rounded end of the housing. The cap can for example be a screw cap and the housing can comprise a thread mating with the thread of the screw cap. In case of a cylindrical body, the thread of the housing can be on the inside or the outside of the cylindrical part of the housing. The marking mentioned above can be provided on the cap. The light emitting surface mentioned above can be part of the cap or provided next to the cap, wherein “next” for example means within 2 %, 5 %, 10 % or 20 % of the extent of the housing in the longitudinal direction.

[0037] In one embodiment, there is a seal between the cap and the housing. This seal protects the inside of the housing from stain and in particular liquids or fluids. Instead of a cap, any kind of lid or closure can be used to close the opening. Instead of a screw fitting, any other technique for securing the cap, lid or closure to the rest of the housing can be used. One alternative example comprises one or more flexible tongues on one of the cap and the housing, each tongue carrying a hook, and a corresponding number of recesses in the other one of the cap and the housing such that the hooks can engage with the recesses.

[0038] In one embodiment, the electronics unit further comprises a gripping surface on the circumferential, or outer, surface of the housing. Said gripping surface is preferably near one longitudinal end of the housing, in particular near the longitudinal end opposite to the longitudinal end which is inserted into the sterile receiving element first. In the terminology used above, the gripping surface is at the longitudinal end of the housing which is at the opposite end of the housing, in the longitudinal direction, to the first longitudinal end that is rounded. In this context, “near to a longitudinal end” for example means within 10 %, 15 %, 20 % or 25 % from said longitudinal end in the longitudinal direction.

[0039] The term “circumferential surface” means the surface of the housing except for the end surfaces, which are typically the surfaces through which the longitudinal axis extends. In case of a cylindrical housing or a polygonal housing, the circumferential surface is the lateral surface. The term “circumferential direction” means a direction which encircles the housing about the longitudinal axis.

[0040] The gripping surface can be any surface which facilitates the handling of the electronics unit when it is held by a person or a tool. In one implementation, the gripping surface comprises recesses, for example one or more recesses distributed along the circumferential direction of the housing. In another implementation, the gripping surface comprises one or more circumferential recesses or protrusions, wherein a recess or protrusion can comprise interruptions along the circumferential direction. An interruption means that there is no recess or protrusion in the section of the interruption. Two or more interruptions can divide the recess or protrusion into multiple segments in the circumferential direction. In one specific implementation, the gripping surface comprises two, three or more parallel rings of recesses or protrusions stacked in the longitudinal direction.

[0041] In one embodiment, the electric contacts are configured to mate with electric contacts of a loading dock. The loading dock is a device for storing and / or charging the electronics unit. Charging means charging a battery provided in the electronics unit. The electric contacts of the dock and the electronics unit establish an electrical connection between the dock and the electronics unit. This electrical contact cannot only be used for charging the electronics unit, but also for transmitting data, in particular from the dock to the electronics unit, for example in terms of a software update.

[0042] The invention further relates to a system comprising the re-usable, non-sterile electronics unit and a loading dock for accommodating the electronics unit and having electric contacts for mating with the electric contacts of the housing.

[0043] The invention further relates to a system comprising the re-usable, non-sterile electronics unit and a sterile receiving element for receiving the electronics unit in a sealed manner. The level of sealing depends on the intended use of the system and can range from a sealing against splash water and / or a sealing against dust up to a hermetical sealing.

[0044] Hermetically sealed does in this case mean that any contaminations the electronics unit might carry do not reach outside of the receiving element. The non-sterile electronics unit does thus not contaminate the sterile field and pose a risk to the patient. The sterile field is an area relative to the patient which is supposed to remain sterile during a treatment of the patient.

[0045] In this context, the term “sterile” means that the receiving element has undergone a sterilization process, for example gas sterilization with ethylene oxide gas, vapor sterilization or treatment with a sterilizing liquid. “Sterile” thus means a state which is generally accepted as being sterile in the medical field. In one embodiment, the sterile receiving element has electric contacts and the electric contacts of the housing are configured to mate with the electric contacts of the sterile receiving element. The electronics unit can be configured to determine that it is correctly positioned in the sterile receiving element if its electric contacts are in contact with the electric contacts of the sterile receiving element.

[0046] In one embodiment, the sterile receiving element has a translucent or transparent area such that the light emitted by the light emitting surface of the electronics unit can be guided to the outside of the sterile receiving element. When the electronics unit is positioned in the sterile receiving element, the translucent or transparent area is preferably positioned opposite to, and in particular in contact with, the light emitting surface.

[0047] The receiving element can be disposable. In this context, the term “disposable” means that the receiving element is envisaged for one-time use only. The disposable receiving element is disposed after this single use. In this context, the system is cost effective since the electronics unit is not disposed together with the receiving element. This is particularly advantageous in that cheap medical instruments can be made to work with magnetic tracking.

[0048] The receiving element can also be a holder, such as a patient reference attached to a patient, for example to the head of the patient. The electronics unit attached to the patient via the receiving element can be used to track the position of the patient, or of a part of the patient. Depending on the use case, the holder need not necessarily be sterile, for example if it is located outside the sterile field. The holder can be simple attachment means for the electronics unit or may comprise one or more magnetometer sensors. The magnetometer sensor may be provided in a sensor housing separate from an electronics housing which accommodates the electronics unit. The sensor housing and the electronics housing can be connected by a cable.

[0049] In a state in which the system is ready to use, the electronics unit is located inside the receiving element. Since the electronics unit is sealed, in particular hermetically sealed, inside the sterile receiving element, the system of the electronics unit and the receiving element is sterile.

[0050] The system preferably further comprises a battery or any other energy storage. The battery stores electrical energy to power the sensor interface unit and the wireless communication module. The battery might be rechargeable.

[0051] In one implementation, the battery is located in the receiving element and the plurality of electric contacts of the electronics unit and the receiving element comprise battery contacts for electrically connecting the battery to the electronics unit. The energy stored in the battery can thus be transported to the components within the electronics unit to drive them. In this implementation, the battery is not located in the electronics unit. The advantage of this implementation is that reusability of the electronics unit is not limited by the storage capacity of the battery since the electronics unit is powered externally.

[0052] In an alternative implementation, the battery is located inside the electronics unit. In this case, the electronics unit is completely self-contained and comprises all components necessary for use in magnetic tracking. In this alternative, the battery can be rechargeable from outside of the electronics unit, for example via the electric contacts.

[0053] As mentioned above, there are many possible types of receiving element.

[0054] In one embodiment, the receiving element is a sterile case comprising a mechanical connector for connecting the sterile case to a medical instrument. The mechanical connector is capable of rigidly attaching the sterile case to the medical instrument. In this document, “rigidly attaching” means that a first component rigidly attached to a second component has a fixed relative position to the second component. The attachment is rigid if the forces typically occurring during use do not change the relative position between the elements.

[0055] In this embodiment, the electronics unit is rigidly attached or held inside of the sterile case. This means that, overall, the electronics unit is rigidly attached to the medical instrument via the sterile case and the mechanical connector. The relative position between the medical instrument and the electronics unit is thus constant during use.

[0056] An advantage of the present embodiment is that the non-sterile electronics unit inside the sterile case can be attached to a sterile medical instrument. In this case, the combination of the medical instrument and the electronics unit inside the sterile case is sterile.

[0057] As an option, the system further comprises a medical instrument having a mechanical connector connectable to the mechanical connector of the sterile case. In use, the sterile case is rigidly attached to the medical instrument via the mechanical connectors of the sterile case and of the medical instrument. The system thus comprises the medical instrument, the sterile case and the electronics unit.

[0058] The electronics unit can be rigidly held in the sterile case via the electric contacts of the electronics unit. In addition or as an alternative, the sterile case might have a cavity having a mating or inverse shape to the shape of the electronics unit, such that the electronics unit is held in the sterile case in a rigid manner.

[0059] In this embodiment, the relative position between the electronics unit and the medical instrument is constant during use. This means that the medical instrument can be tracked by tracking the electronics unit. In this case, tracking involves that the electronics unit sends the output data of the internal magnetometer sensor(s) inside the electronics unit to the computing unit. The computing unit determines the position of the electronics unit, and thus of the medical instrument, in a tracking reference system, like a reference system of the field generator, from the predetermined positions of the at least one magnetometer sensor in the electronics unit. The technology of magnetic tracking is known and thus not described here in detail.

[0060] In some use cases, it is desired to track a particular point of interest of the medical instrument. In this case, the electronics unit has to be calibrated with the point of interest of the medical instrument. This means that the location of the point of interest relative to the electronics unit is determined such that the computing unit can calculate the location of the point of interest of the medical instrument in the tracking reference system.

[0061] Calibration of the electronics unit with the point of interest of the medical instrument can be performed in many ways. In one approach, the point of interest is brought into a defined location in the tracking reference system, like a predetermined point on the surface of the field generator. The location of the point of interest of the medical instrument in the tracking reference system is thus known. The position of the electronics unit is measured using the magnetic tracking system. The computing unit calculates the calibration from those two information.

[0062] In another approach, a calibration tool is used. The calibration tool comprises a reference point against which the point of interest of the medical instrument is held. The position of the calibration tool in the tracking reference system is measured, for example using the magnetic tracking system. The geometry of the calibration tool is known to the computing unit. In this case, the geometry means the location of the reference point on the calibration tool. The computing unit calculates the calibration from the measured positions of the electronics unit and of the calibration tool in the tracking reference system and from the known geometry of the calibration tool.

[0063] The calibration tool can for example be a device having a portion with a shape inverse to the shape of the medical instrument around the point of interest or a notch for receiving the point of interest. The medical instrument can thus be mated with the calibration tool for calibration. As another example, the calibration tool can be a tracked pointer. The tip of the pointer is held against the point of interest of the medical instrument for calibration.

[0064] In one embodiment, the receiving element is a medical instrument. The subsequent embodiments are particularly useful if the receiving element is a medical instrument, but they are not limited to this. A medical instrument can for example be a pointer, a stylet or a suction device.

[0065] In this embodiment, the electronics unit is not located in a sterile case which in turn is attached to a medical instrument, but directly in the medical instrument. The electronics unit is rigidly attached to the medical instrument in analogy to the embodiment described above in which the receiving element is a sterile case.

[0066] The medical instrument being the receiving unit is sterile and accommodates the electronics unit inside such that contaminations of the electronics unit do not reach to the outside of the medical instrument.

[0067] The medical instrument may have electric contacts to mate with the electric contacts of the electronics unit such that the electronics unit can be connected to electronic components of the medical instrument.

[0068] In one embodiment, the sensor interface unit is configured to process user input data, for example in terms of a trigger signal input to the sensor interface unit by operation of a button of the medical instrument. The button of the medical instrument, or any other user input acquisition unit, is connected to the sensor interface unit via the electric contacts of the medical instrument and the electric contacts of the electronics unit. The sensor interface unit provides the information on the user input, for example the information that the button of the medical instrument was pushed, to the wireless communication module, which in turn transmits this information to the computing unit. The computing unit can then trigger a function, like sampling of a point, making a screenshot or any other function associated with the user input.

[0069] In one embodiment, the system further comprises at least one magnetometer sensor in the receiving element, wherein the plurality of electric contacts of the electronics unit comprise data contacts connectable to the at least one magnetometer sensor in the receiving element and connected to the sensor interface unit in the electronics unit.

[0070] The magnetometer sensor(s) in the receiving element are referred to as external magnetometer sensor(s) since they are external to the electronics unit. The external magnetometer sensors may be located at different positions of the receiving element. This means that the distance between the external magnetometer sensors can be larger than the distance between internal magnetometer sensors in the electronics unit, which means that it is possible to detect the strength of the magnetic field at positions distributed over a larger area, which can improve the tracking result. Therefore, in one embodiment, the sensor interface unit is configured to process the sensor data received from a magnetometer sensor in the receiving element. The electronics unit thus processes the output of the external magnetometer sensor and transmits it to the computing unit. This can be in addition to the output of one or more internal magnetometer sensors within the electronics unit. The computing unit can thus receive and process the output of one or more external magnetometer sensors and optionally the output of one or more internal magnetometer sensors.

[0071] In one embodiment, the system further comprises a calibration data memory in the receiving element, the calibration data memory storing calibration data of the receiving element. In one implementation, the calibration data represents the location of a point of interest of the receiving element relative to the at least one magnetometer sensor of the receiving element. Alternatively, the calibration data represents the positions of the at least one magnetometer sensor relative to the location of the point of interest of the receiving element. With the calibration data memory, it is not necessary to calibrate the electronics unit with the medical instrument since the information required to calculate the location of the point of interest of the medical instrument in the tracking reference system from the positions of the external magnetometer sensors(s) in the tracking reference system is comprised in the calibration data.

[0072] The calibration data memory, like any other memory that is mentioned in this document, can be of any suitable kind, such as a RAM, a ROM, a flash memory or any kind of chip or storage that can be read.

[0073] In one implementation, the receiving element comprises calibration data contacts connected to the calibration data memory and configured to mate with electric contacts of the electronics unit. The electronics unit can thus read the calibration data from the calibration data memory and transmit them to the computing unit via the wireless communication module. The computing unit can then use the calibration data to calculate the location of the point of interest of the receiving element.

[0074] The calibration data can represent the location of the point of interest of the receiving element relative to the cavity which accommodates the electronics unit or relative to the electric contacts of the receiving element which contact the electric contacts of the electronics unit. The combination of such calibration data and the predetermined position of an internal magnetometer sensor in the electronics unit defines the location of the point of interest of the receiving element relative to the position of the internal magnetometer sensor. The computing unit might use this information for calculating the location of the point of interest of the receiving element if the sensor data of the internal magnetometer sensor is transmitted to the computing unit.

[0075] In one embodiment, the calibration data represents a unique identifier of the receiving element. The electronics unit transmits the unique identifier to the computing unit. The computing unit may retrieve stored calibration data, for example from a database, corresponding to the unique identifier. The stored calibration data can represent the location of a point of interest of the receiving element relative to the at least one magnetometer sensor of the receiving element, the location of the point of interest of the receiving element relative to the cavity which accommodates the electronics unit or relative to electric contacts of the receiving element which contact the electric contacts of the electronics unit, a combination thereof or further data.

[0076] Receiving the unique identifier at the computing unit may indicate that a medical instrument associated with this unique identifier is actually used. The computing unit may store the unique identifier together with a counter representing the number of times the unique identifier has been received, and may thus store how often the medical instrument has been used. The computing unit may output a warning signal, like an optical or acoustical signal, if the maximum number of allowable uses of the medical instrument has been reached or exceeded. One example are single use instruments which may only be used once. The computing unit may also transmit a corresponding information to the electronics unit. The wireless communication module in the electronics unit receives this information and the electronics unit controls a light emitting element to signal this information by using light for example as described above.

[0077] The computing unit may increase the stored counter not every time the unique identifier is received since the unique identifier might be received multiple times during the same procedure. The counter may for example only be increased if a minimum time has elapsed since the previous increase of the counter when receiving the unique identifier.

[0078] The electronics unit can be configured to receive other data via its electric contacts. The other data can be provided by the sterile receiving element, in particular if it is a medical instrument. The sterile receiving element can comprise input means for receiving user input, wherein the input means can for example be one or more of a button, a touch sensitive surface or a joystick. The other data is then user input data.

[0079] The sterile receiving element may comprise a measurement sensor and the other data can be the output data of the measurement sensor. If the receiving element is a medical instrument, the other data can also be instrument data, which can comprise identification data identifying the type of instrument or instrument status data, which for example indicates a use counter which represents the number of times the medical instrument has been used.

[0080] The electronics unit can process the other data, transmit the other data to the computing unit via the wireless communication module or a combination thereof.

[0081] The electric contacts can comprise dedicated contacts for different purposes, like dedicated contacts for connection to a battery, for connection to input means, for transmission of the calibration data and so on. On the other hand, the same contacts can be used for different purposes, for example by time staggering the different purposes or by using different transmission techniques which do not interfere with each other.

[0082] In one embodiment, the electronics unit further comprises at least one inertia sensor. An inertia sensor can detect accelerations acting on the electronics unit, which may include gravity, in particular the direction of gravity. The sensor interface unit can process the output of the inertia sensor and transmit the processed result to the computing unit via the wireless communication unit. The computing unit can use the data delivered by the inertia sensor, in addition to the data delivered by the magnetometer sensor(s), to calculate the position of the electronics unit or of the receiving element in the tracking reference system. In addition or as an alternative, at least one inertia sensor is provided in the receiving element. Those inertia sensors are referred to as external inertia sensors since there are not located inside the electronics unit. In this case, the electronic contacts of the electronics unit comprise inertia sensor contacts connectable to the at least external inertia sensor, either directly or via one or more conductors. The data collected by the external inertia sensor(s) can be processed in the same manner as the data collected by the inertia sensor(s) inside the electronics unit.

[0083] In one embodiment, the sensor interface unit is configured to determine in which kind of receiving element the electronics unit is located. In particular, the sensor interface unit is configured to determine whether the receiving element is a sterile case, a medical instrument or a holder.

[0084] If the receiving unit is a sterile case or a holder, no external magnetometer sensor(s) and typically no calibration data memory are connected to the electric contacts of the electronics unit. The sensor interface unit recognizes that there is no input of such sensors and no calibration data can be read, and thus determines that the receiving element is a sterile case or a holder. If the sensor interface unit detects sensor data input to the electric contacts or a calibration data memory connected to the electronics unit, it determines that the receiving element is a medical instrument.

[0085] On the other hand, each kind of receiving element could comprise a memory which stores the kind of receiving element, for example in terms of the unique identifier. The sensor interface unit reads the data from the memory and determines the kind of receiving element from this data.

[0086] The sensor interface unit may determine the kind of receiving element using mechanical properties. For example, the receiving element may comprise a mechanical pin which presses against a predetermined position on the surface of the electronics unit and the electronics unit detects that pressure is exerted thereon. The electronics unit may thus comprise one or more pressure detectors, each of them configured to detect pressure on a predetermined area of the electronics unit. One pressure detector may be sufficient if it is only used to distinguish between a sterile case and a holder, while a medical instrument is identified via data stored in a memory of the medical instrument. For example, the holder may comprise a pin to exert pressure on the electronics unit and the sterile case may not. However, the electronics unit may comprise multiple pressure sensors and the receiving element may comprise a combination of pins that identifies the kind of receiving element.

[0087] As an alternative, the receiving element may comprise an interruption element. The interruption element is configured to interrupt a circuit in the electronics unit, such as an electric circuit or a light circuit which guides light. The kind of receiving element can be identified from whether the circuit is interrupted or not. In analogy to the previous example, the receiving element can comprise one or more interruption elements and the electronics unit may comprise on or more circuits which can be interrupted.

[0088] The sensor interface unit may transmit the determined kind of receiving element, or the unique identifier if applicable, to the computing unit via the wireless communication module. The computing unit can then trigger an appropriate application, function or workflow.

[0089] If the electronics unit is located in a sterile case, the computing unit can for example trigger a calibration workflow in which the location of a point of interest of a medical instrument relative to the electronics unit is measured as described above.

[0090] If the electronics unit is located in a holder, the computing unit can use the electronics unit as a reference for the patient. This means that a reference system associated with the electronics unit in the holder is used for other spatial information, such as the position of a point of interest of a medical instrument. It is possible to calculate a transformation from the reference system of the field generator into the reference system of the electronics unit in the holder.

[0091] The computing unit to which the wireless communication module transmits the sensor data after processing by the sensor interface unit can be part of the system or not. The computing unit is configured to receive the sensor data from the electronics unit. The computing unit can be integrated into a tracking base station which comprises a magnetic field source for the electromagnetic tracking. The tracking base station can also be part of the system.

[0092] The tracking base station can further comprise a wireless communication module for receiving the sensor data from the electronics unit and forwarding them to the computing unit. The wireless communication module can also be used to transmit data to the wireless communication module of the electronics unit. The wireless communication module is not necessarily a part of the tracking base station and can, for example, be part of the computing unit or a separate component.

[0093] In one embodiment, the electronics unit is configured to automatically power up if it is inserted into the receiving element. The electronics unit is thus switched off or in a sleep mode when it is not inside the receiving element, thus saving energy. Powering up the electronics unit for example means activating the sensor interface unit and / or the wireless communication module.

[0094] In one implementation, the electronics unit powers up if its electric contacts are in contact with electronic contacts of the receiving element. The electronics unit for example powers up if it is supplied with energy from a battery in the receiving element or it is connected to a memory, like the calibration data memory, in the receiving element.

[0095] In another example, a power circuit which connects a battery in the electronics unit and the sensor interface unit and / or the wireless communication module is open when the electronics unit is not in the receiving element and closed if it is. The power circuit may comprise a switch operated by the receiving element or two electric contacts which are bridged by the receiving element.

[0096] DEFINITIONS

[0097] In this section, definitions for specific terminology used in this disclosure are offered which also form part of the present disclosure. Pointer

[0098] A pointer is a rod which comprises one or more - advantageously, two - magnetometer sensors 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 magnetometer sensors attached to the pointer) to the position corresponding to the coordinates, such that the position of the pointer can be determined by using a surgical navigation system to detect the positions of the magnetometer sensor on the pointer. The relative location between the magnetometer sensors 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.

[0099] Fixed (relative) position

[0100] 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). BRIEF DESCRIPTION OF THE DRAWINGS

[0101] 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

[0102] Fig. 1 schematically shows an electronics unit;

[0103] Fig. 2 shows the electronics unit of figure 1 in a sterile case attached to a medical instrument;

[0104] Fig. 3 shows another medical instrument in which the electronics unit of figure 1 is incorporated;

[0105] Fig. 4 shows a tracking environment using the medical instrument of figure 3;

[0106] Fig. 5 shows a holder for the electronics unit of figure 1 ;

[0107] Fig. 6 shows different views of a particular design of the electronics unit;

[0108] Fig. 7 shows a particular design of a marking; and

[0109] Fig. 8 shows another example of a holder.

[0110] DESCRIPTION OF EMBODIMENTS

[0111] Figure 1 schematically shows a re-usable, non-sterile electronics unit 1. The electronics unit 1 comprises a housing 2 in which two magnetometer sensors 3, a sensor interface unit 4 and a wireless communication module 5 are disposed. Instead of two magnetometer sensors 3, only one magnetometer sensor or more than two magnetometer sensors can be provided. As an option, the electronics unit 1 can comprise one or more inertia sensors (not shown).

[0112] The electronics unit 1 further comprises electric contacts 6 reaching to the outside of the housing 2 such that they can be connected to components external to the housing 2. In the present example, three electric contacts 6 are shown, but there can be more or fewer electric contacts as required. External components can include one or more of a battery to power the electronics unit 1 , a magnetometer sensor and a memory. The magnetometer sensors 3 are electrically connected to the sensor interface unit 4 such that the sensor interface unit 4 can receive data or signals generated by the magnetometer sensors 3. The magnetometer sensors 3 in particular output data or a signal corresponding to the strength of a magnetic field sensed by the magnetometer sensors 3. The magnetometer sensors 3 are provided at predetermined positions in the housing 2.

[0113] The sensor interface unit 4 receives the output of a magnetometer sensor, such as the magnetometer sensors 3, and processes it. If the magnetometer sensor outputs an analog signal, the sensor interface unit 4 performs analog-digital conversion of the analog signal and samples the converted signal. If the magnetometer sensor outputs a digital signal, the sensor interface unit receives and processes this digital signal. The sensor interface unit 4 transmits the processed data via the wireless communication module 5.

[0114] The electronics unit 1 can comprise a battery within the housing 2 to power the sensor interface unit 4 and the wireless communication module 5. It optionally powers the magnetometer sensors 3 if they require power to detect the strength of the magnetic field. In addition or as an alternative, the electronics unit 1 is connected to an external battery, which is external to the electronics unit 1 , via the electric contacts 6 to supply power to the electronics unit 1 .

[0115] Figure 2 shows a system comprising the electronics unit 1 and a sterile case 7 as a receiving element for the electronics unit 1. The sterile case 7 as an example of the sterile receiving element encapsulates the electronics unit 1 such that it is sealed therein, for example hermetically. This means that contaminations of the electronics unit 1 do not reach outside of the case 7.

[0116] The case 7 has a cavity with a shape which exactly matches the shape of the housing 2 of the electronics unit 1 such that the electronics unit 1 has a fixed position relative to the case 7. The medical instrument 8 and the case 7 each have a mechanical connector (not shown) which form a mechanical interface and can mate with each other to rigidly attach the case 7 to the medical instrument 8. The two mechanical connectors can form a (releasable) geometry, such as a positive locking, or just form contact surfaces which are connected via means like a screw or a bolt.

[0117] In the example shown in figure 2, a battery to power the electronics unit 2 can be located within the electronics unit 2 or within the case 7. In the latter case, the battery is connected to the electronics unit 2 via the electric contacts 6.

[0118] With the electronics unit 1 firmly held by the case 7 and the case 7 being rigidly attached to the medical instrument 8, the position of the electronics unit 1 , and in particular of the magnetometer sensors 3 in the electronics unit 1 , relative to the medical instrument 8 is constant, such that the position of the medical instrument 8 is associated with the position of the electronics unit 1 . The position of the medical instrument 8 can thus be derived from the position of the electronics unit 1 , which in turn can be derived from the locations of the magnetometer sensors 3 of the electronics unit 1 and their positions therein.

[0119] The medical instrument 8 has a point of interest in terms of its tip 8a. In some use cases, the location of the tip 8a might be of interest. In this case, the location of the tip relative to the electronics unit 1 is measured, for example by measuring the position of the electronics unit 1 using the output of its magnetometer sensors 3 and measuring the location of the tip 8a using a calibration device such as a pointer. This is also referred to as calibration. By tracking the electronics unit 1 and applying the calibration, the location of the tip 8a can be tracked.

[0120] Figure 3 shows another instrument 9 having a sealable cavity 11 which accommodates the electronics unit 1 therein in a (hermetically) sealed manner as indicated by the arrow. The electric contacts 6 of the electronics unit are connected to electric contacts 12 of the medical instrument 9. The medical instrument 9 is an example of the sterile receiving element.

[0121] The medical instrument 9 comprises a magnetometer sensor 13 connected to the electronics unit 1 via the electric contacts 12 of the medical instrument 9 and the electric contacts 6 of the electronics unit 1 . The sensor interface unit 4 reads and processes the output of the magnetometer sensor 13 and transmits the result via the wireless communication module 5. The sensor interface unit 4 associates each data item representing the strength of the magnetic field as detected by a magnetometer sensor 13 with the identification of the magnetometer sensor 13 which has measured the corresponding strength or with a position of said magnetometer sensor 13 relative to the electronics unit 1 . The tracking system described later can thus identify at which location of the medical instrument 9 which strength of the magnetic field was measured.

[0122] The medical instrument 9 further comprises a calibration data memory 14 connected to the electronics unit 1 via the electric contacts 12 of the medical instrument and the electric contacts 6 of the electronics unit 1. The calibration data memory stores calibration data which is read by the sensor interface unit 4 and transmitted via the wireless communication module 5. The calibration data for example represents the position of the magnetometer sensor 13 in the medical instrument 9, in particular relative to a point of interest of the medical instrument 9, like the tip 10 of the medical instrument 9. Alternatively, the calibration data for example represents the location of the tip 10 relative to the position of the magnetometer sensor 13.

[0123] The medical instrument 9 may comprise two or more magnetometer sensors 13 and the calibration data memory 14 preferably stores calibration data for each of the magnetometer sensors 13 of the medical instrument 9.

[0124] When placed in the cavity 11 , the position of the electronics unit 1 relative to the medical instrument is optionally fixed, for example by the electric contacts 6 of the electronics unit 1 and the electric contacts 12 of the medical instrument 9 engaging with each other, by partial or full form fit of the electronics unit 1 in the cavity 11 or a combination thereof. The position of the electronics unit 1 relative to the medical instrument 9 is known, for example from the geometry of the medical instrument 9 or a calibration of the system. The sensor interface unit 4 then optionally also reads and processes the output of the magnetometer sensors 3 and transmits the result via the wireless communication module 5 in analogy to the output of the magnetometer sensors 13. This in particular means that the identification of the magnetometer sensor 3 which has measured the strength of the magnetic field or the position of the magnetometer sensor 3 is transmitted. The tracking system has thus additional information for tracking the medical instrument 9.

[0125] With the calibration data memory 14, the medical instrument 9 is pre-calibrated and there is no need to calibrate the medical instrument 9 in situ. In addition, the magnetometer sensors 13 can be distributed over the medical instrument 9 such that the strength of the magnetic field can be measured at locations which are spatially distinct.

[0126] Figure 4 shows a tracking environment in which a tracking system comprising a computing unit 15 and a field generator 16 is employed. The field generator generates a variable magnetic field to be detected by the magnetometer sensors. The computing unit 15 receives the data transmitted by the wireless communication module 5 and calculates the location of the magnetometer sensors in a tracking reference system, which is for example defined relative to the field generator 16. A receiver for receiving the data transmitted by the wireless communication module 5 of the electronics unit 1 may be provided in the field generator 16 or in the computing unit 15.

[0127] In the example shown in figure 4, the medical instrument 9 is used to sample points of a patient P. The computing unit 15 calculates the locations of the sampled points in the tracking reference system.

[0128] Figure 5 shows a holder 17 for an electronics unit 1. The holder 17 is attached to the patient P, for example to the forehead of the patient P. The holder 17 is for example attached using an adhesive or a tape. With the electronics unit 1 attached to the patient P, movement of the patient relative to the field generator 16 can be tracked. In addition, the patient P can be registered in the tracking reference system, for example by sampling multiple points on the surface of the patient using the medical instrument 9. If the patient P is registered in the tracking reference system, the tracking system can calculate the position of a tracked object, like the medical instrument 9, relative to the patient P.

[0129] The electronics unit 1 can optionally comprise one or more inertia sensors which detect accelerations of the electronics unit 1. The output of the inertia sensor(s) is processed by the sensor interface unit 4 and transmitted to the computing unit 15 via the wireless communication module 5. The computing unit 15 uses the output of the inertia sensor(s) when calculating the position of the electronics unit 1 . Instead of or in addition to the inertia sensor(s) in the electronics unit, one or more inertia sensors can be provided in the sterile case 7, in the medical instrument 9 or in the holder 17. Those inertia sensors are connected to the electronics unit 1 via the electric contacts 6.

[0130] Figure 6 shows a particular design of the electronics unit 1 from different viewing angles. In this particular design, the housing 2 has an elongated shape along a longitudinal axis A which passes through the housing 2. In the particular embodiment shown in figure 6, the housing 2 has a cylindrical main body 18 with the longitudinal axis A as its axis of rotation. However, the main body 18 is not exactly cylindrical, but has three flat sides 19 extending along a part of the longitudinal extent of the main body 18.

[0131] The housing 2 has two opposite ends in the longitudinal direction, wherein the first longitudinal end 20 is rounded, in particular in the shape of a hemisphere, and the second longitudinal end is an open end closed by a cap 22. The two magnetometer sensors 3, the sensor interface unit 4 and the wireless communication module 5 are located within the housing, wherein at least the two magnetometer sensors 3 have a predetermined and fixed position relative to the housing 2.

[0132] The flat sides 19 extend from the first longitudinal end 20 towards the second longitudinal end, but only along a part of the longitudinal extent of the housing 2. In the present example, the flat sides extend towards the second longitudinal end up to a distance of about 20 % of the longitudinal extent of the housing away from the second longitudinal end. However, the flat sides 19 can be longer or shorter.

[0133] The flat sides 19 are non-uniformly distributed on the housing 2 along the circumferential direction, which is perpendicular to the longitudinal direction. In the present embodiment, the three flat sides 19 are arranged at an angle of 90 degrees between two neighboring flat sides 19 along the circumferential direction. In other words, the three flat sides 19 are arranged at 0 degrees, 90 degrees and 180 degrees in the circumferential direction. With this distribution, there is only one rotational alignment of the housing 2 relative to a mating receiving element in which the electronics unit 1 can be inserted into the receiving element. The electronics unit 1 is to be inserted into the receiving element with the first longitudinal end first.

[0134] In this example, the electric contacts 6 are positioned on the first longitudinal end side of one of the flat sides 19, for example the central flat sides which is in the middle between the two other flat sides 19, but could also be positioned on other surfaces, for example on two or more of the flat sides 19 or on the rounded first longitudinal end 20.

[0135] At the second longitudinal end, the housing 2 has an inner thread and the cap 22 has an outer thread to mate with said inner thread. The housing 2 can thus be opened, for example for inserting or changing the internal components of the electronics unit 1. The cap 22 has a marking 24 which can be used for identifying the rotational alignment of the housing 2 about the longitudinal axis A, for example when inserting the electronics unit 1 into a receiving element.

[0136] Near the cap 22, the housing has a light emitting surface 21 . The light emitting surface is ring-shaped and completely surrounds the longitudinal axis A in a circumferential direction. The light emitting surface 21 can be the surface of a light emitting element embedded into the housing 2 or a translucent or transparent section of the housing 2 which allows light emitted by a light emitting element within the housing 2 to be visible from the outside of the housing 2. The light emitting surface 21 is for example farther away from the second longitudinal end than the deep end of the inner thread of the housing 2.

[0137] The housing 2 further has an optional gripping surface 23 on the circumferential surface of the housing 2. In this embodiment, the gripping surface is formed by parallel segments of circumferential protrusions, wherein the lengths of the segments decrease with increasing distance of the protrusion from the second longitudinal end. On each circumferential line, there can be two or more circumferential segments of a circumferential protrusion, wherein the circumferential segments are for example equally distributed along the circumferential direction. In the present embodiment, the parallel segments are centered, in the circumferential direction, about the positions of two of the flat sides 19 in the circumferential direction. In other words, the gripping surface 23 consists of two parts, and each of the parts is located at the virtual extension of said two flat sides 29 in the longitudinal direction. Said two flat sides 29 are those which are 180 degrees apart in the circumferential direction.

[0138] The gripping surface is positioned close to the second longitudinal end of the housing 2, in particular in a range between 5 % and 30 % away from the second longitudinal end of the housing 2 in the longitudinal direction. The light emitting surface 21 is for example located between the cap 22 and the gripping surface 23.

[0139] Each of the rounded shape of the first longitudinal end 20, the light emitting surface 21 , the cap 22 and the gripping surface 23 is optional and the invention encompasses any combination of those features.

[0140] Figure 7 shows an exemplary design of the marking 24 in more detail. In this design, the marking 24 is a protrusion on the end face of the cap 22. The marking 24 is a protrusion having the shape of a triangle when viewed in the longitudinal direction, which is perpendicular to the end face of the cap 22. The specific design shown in figure 7 has an isosceles triangle which is mirror symmetric to a radius of the cap 22, wherein the first corner which lies on the radius to which the triangle is symmetric lies radially outwards compared to the second and third corners. The lengths of the three sides of the triangle can be identical, or only the lengths of the two sides which are not perpendicular to the radius are identical. The lengths of the three sides are between 40 % and 60% of the radius of the cap 22.

[0141] The cap 22 further comprises two optional protrusions 25 in the shape of concentric circular arcs on its end face. The openings of the two concentric circular arcs are mirror symmetric to the radius to which the triangle forming the marking 24 is mirror symmetric. The second and third corners of the triangle are located on a virtual circular arc which would supplement the inner circular arc to a full circle. The first corner of the triangle is located radially outwards of the outer circular arc. The distances between the respective ends of the circular arcs and the triangle are less than 20 % of the length of the shortest side of the triangle. The protruding heights of the marking 24 and the circular arcs over the end face of the cap 22 are identical.

[0142] When the cap 22 is attached to the rest of the housing 2, the radius on which the first corner of the triangle lies is at the same circumferential position as the central one of the three flat side 19.

[0143] In the example shown in figure 7, the color of the cap 22 is black and the color of the marking 24 is grey, but any other color scheme can be used.

[0144] The main body 18 of the housing 2 is not necessarily cylindrical, but can have a polygonal cross-section in a plane perpendicular to the longitudinal axis A. The polygonal cross-section is for example non-regular, such that the electronics unit 1 can be inserted into a correspondingly shaped receiving element in one rotational alignment about the longitudinal axis A only.

[0145] Figure 8 shows another example of a holder 26 as an embodiment of a receiving element. The holder 26 consists of an electronics housing 26a for accommodating the electronics unit 3 in a sterile manner, a sensor housing 26c comprising one or more magnetometer sensors and a cable 26b connecting the magnetometer sensor(s) in the sensor housing 26c and the electronics unit 3 in the electronics housing. The cable 26b may be directly connected to the magnetometer sensors in the sensor housing 26c. The other end of the cable 26b may be connected to electric contacts in the electronics housing 26a, which in turn are in contact with the electric contacts 6 of the electronics unit.

[0146] The sensor housing can be attached to a patient, such that the patient can be tracked using the output of the magnetometer sensors in the sensor housing 26c. The electronics housing 26a can be positioned as desired, for example next to the patient, but can also be attached to the patient. For attachment to the patient or another object, the electronics housing 26a can have a clip or any other attachment means. In this embodiment, the electronics housing 26a can have a translucent or transparent section such that light emitted by a light emitting surface 21 of the electronics unit 3 is visible from outside of the electronics housing 26a.

[0147] The electronics housing 26a is designed to mate with the electronics unit 3. This for example means that it has an interior shape which is inverse to the shape of the housing 2 of the electronics unit 3.

[0148] The complete holder 26 can be provided in a sterile packaging.

[0149] The subsequent embodiments describe examples of another system which can use the re-usable, non-sterile electronics unit described herein and method of preparing a sterile receiving element using said re-usable, non-sterile electronics unit.

[0150] Embodiment 1 : A system for magnetic tracking in a medical environment, the system comprising a re-usable, non-sterile electronics unit (1 ) comprising

[0151] - a housing (2),

[0152] - at least one magnetometer sensor (3),

[0153] - a sensor interface unit (4) configured to process sensor data received from a magnetometer sensor,

[0154] - a wireless communication module (5) configured to transmit the sensor data after processing by the sensor interface unit (4) to a computing unit (15), and

[0155] - a plurality of electric contacts (6) reaching to the outside of the housing (2), wherein the system further comprises a sterile receiving element (7, 9) configured to receive the electronics unit (1 ) in a hermetically sealed manner.

[0156] Embodiment 2: The system of embodiment 1 , wherein the electronics unit (1 ) is located inside the receiving element (7, 9). Embodiment 3: The system of embodiment 2, wherein the sensor interface unit (4) is configured to determine in which kind of receiving element (7, 9) the electronics unit (1 ) is located.

[0157] Embodiment 4: The system of any one of embodiments 1 to 3, further comprising a battery.

[0158] Embodiment 5: The system of embodiment 4, wherein the battery is located in the receiving element (7, 9) and the plurality of electric contacts (6) comprise battery contacts for electrically connecting the battery to the electronics unit (1 ).

[0159] Embodiment 6: The system of any one of embodiments 1 to 5, wherein the sensor interface unit (4) is configured to process the sensor data received from a magnetometer sensor (3) in the electronics unit (1 ).

[0160] Embodiment 7: The system of any one of embodiments 1 to 6, wherein the receiving element is a sterile case (7) comprising a mechanical connector for connecting the sterile case (7) to a medical instrument (8).

[0161] Embodiment 8: The system of embodiment 7, further comprising a medical instrument (8) having a mechanical connector connectable to the mechanical connector of the sterile case (7).

[0162] Embodiment 9: The system of any one of embodiments 1 to 6, further comprising at least one magnetometer sensor (13) in the receiving element (7, 9), wherein the plurality of electric contacts (6) of the electronics unit (1 ) comprise data contacts connectable to the at least one magnetometer sensor (13) in the receiving element (7, 9) and connected to the sensor interface unit (4) in the electronics unit (1 ). Embodiment 10: The system of embodiment 9, wherein the sensor interface unit (4) is configured to process the sensor data received from a magnetometer sensor (13) in the receiving element (7, 9).

[0163] Embodiment 11 : The system of any one of claims 7 to 10, further comprising a calibration data memory (14) in the receiving element (9), the calibration data memory (14) storing calibration data of the receiving element (9).

[0164] Embodiment 12: The system of embodiment 11 , wherein the calibration data represents the location of a point of interest (10) of the receiving element (9) relative to the at least one magnetometer sensor (13) of the receiving element (9).

[0165] Embodiment 13: The system of embodiment 11 , wherein the calibration data represents a unique identifier of the receiving element (9).

[0166] Embodiment 14: The system of any one of embodiments 7 to 13, wherein the receiving element is a medical instrument (9).

[0167] Embodiment 15: The system of any one of embodiments 1 to 14, wherein the electronics unit (1 ) further comprises at least one inertia sensor.

[0168] Embodiment 16: A method of preparing a sterile receiving element (7, 9) for magnetic tracking in a medical environment, comprising the step of disposing a reusable, non-sterile electronics unit (1 ) as defined in embodiment 1 in the sterile receiving element (7, 9) in a hermetically sealed manner.

Claims

CLAIMS1. A re-usable, non-sterile electronics unit (1 ) for use in a system for magnetic tracking in a medical environment, the re-usable, non-sterile electronics unit (1 ) comprising- a housing (2),- at least one magnetometer sensor (3),- a sensor interface unit (4) configured to process sensor data received from a magnetometer sensor,- a wireless communication module (5) configured to transmit the sensor data after processing by the sensor interface unit (4) to a computing unit (15), and- a plurality of electric contacts (6) reaching to the outside of the housing (2), wherein the housing (2) has an elongated shape along a longitudinal axis.

2. The re-usable, non-sterile electronics unit (1 ) of claim 1 , wherein the housing (2) is rotationally asymmetric along at least a part of its longitudinal extent.

3. The re-usable, non-sterile electronics unit (1 ) of claim 1 or 2, wherein the housing (2) has a cylindrical main body (18) with a flat side (19) along at least a part of its longitudinal extent.

4. The re-usable, non-sterile electronics unit (1 ) of claim 1 or 2, wherein the housing (2) has a polygonal cross-section.

5. The re-usable, non-sterile electronics unit (1 ) of any one of claims 1 to 4, wherein a first longitudinal end (20) of the housing is rounded.

6. The re-usable, non-sterile electronics unit (1 ) of any one of claims 1 to 5, wherein the housing (2) has a light emitting surface (21 ) at a second longitudinal end.

7. The re-usable, non-sterile electronics unit (1 ) of claim 6, wherein the light emitting surface (21 ) is located in a range between 1 % and 10 % of the longitudinal length of the housing (2) away from the second longitudinal end.

8. The re-usable, non-sterile electronics unit (1 ) of claim 6 or 7, wherein the light emitting surface (21 ) is made of a translucent material and the electronics unit (1 ) comprises a light emitting element inside the housing (2).

9. The re-usable, non-sterile electronics unit (1 ) of any one of claims 6 to 8, wherein the electronics unit (1 ) is configured to indicate its status via the light emitting surface (21 ).

10. The re-usable, non-sterile electronics unit (1 ) of any one of claims 1 to 9, further comprising a visual marking (24) on the front face of a longitudinal end of the housing (2).11 . The re-usable, non-sterile electronics unit (1 ) of any one of claims 1 to 10, further comprising a gripping surface (23) on the circumferential surface of the housing (2).

12. The re-usable, non-sterile electronics unit (1 ) of any one of claims 1 to 11 , wherein the electric contacts (6) are configured to mate with electric contacts of a loading dock.

13. A system comprising the re-usable, non-sterile electronics unit (1 ) of claim 12 and a loading dock for accommodating the electronics unit (1 ) and having electric contacts for mating with the electric contacts (6) of the housing (2).

14. A system comprising the re-usable, non-sterile electronics unit (1 ) of any one of claims 1 to 12 and a sterile receiving element (7, 9) for receiving the electronics unit (1 ) in a sealed manner.

15. The system of claim 14, wherein the electric contacts (6) of the housing (2) are configured to mate with electric contacts of the sterile receiving element (7, 9).

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