Patent Description:
Electromagnetic tracking is used, for example, in certain interventional procedures in order to track devices, e.g. their position and orientation, that are used during the procedures. As an example, a wire connection may be provided to connect an electromagnetic sensor to a computation unit of an electromagnetic tracking system. As a further example, <CIT> describes the synchronization of medical devices via a digital interface. For example, a cardiac catheterization system is described including two catheters. The catheters comprise a wireless digital interface, which communicates with a corresponding interface in a console. The respective counterpart, i.e. the interface in the console, communicates with a central processing unit that receives and processes the data signals conveyed from the two catheters. The catheters may be provided with a position sensor generating signals that are indicative of the position coordinates, for which the position sensors can sense magnetic fields generated by a field generator. As a further example, <CIT> describes a medical device position guidance system having a non-invasive medical device communicable with an invasive medical device. The system provides outputs useful to assess the position of an invasive medical device. A magnetic field is used to gather information about the position of the invasive device. Radio waves are used tocommunicate this information between the noninvasive device and the invasive device. <CIT> describes an apparatus for tracking an object that includes a plurality of field generators, which generate electromagnetic fields at different, respective frequencies in a vicinity of the object, and a radio frequency (RF) driver, which radiates a RF driving field toward the object. A wireless transponder is fixed to the object. The transponder includes at least one sensor coil, in which a signal current flows responsive to the electromagnetic fields, and a power coil, which receives the RF driving field and conveys electrical energy from the driving field to power the transponder. The power coil also transmits an output signal responsive to the signal current to a signal receiver, which processes the signal to determine coordinates of the object.

There may be a need to further improve the tracking of medical devices.

The object of the present invention is solved by the subject-matter of the independent claim <NUM>, wherein further embodiments are incorporated in the dependent claims.

According to the invention, a catheter according to claim <NUM> is provided.

Advantageously, the wireless readout unit enables to further improve the wireless data link due to the pre-processing of the raw signals. In other words, the stream of raw sensor signals is not continuously transferred via the data link to the control unit, but the raw signals are pre-processed and then transferred, and hence a reduction of the data stream, or a partition of the data stream, is enabled, which means an improvement in view of the wireless data link. Hence, also the overall situation in an operational theatre can be improved, since there may be a large number of devices that are connected to the tracking system or that communicate with each other via wireless data links. The pre-processing also makes the communication more reliable.

In an example, the control unit is a processing unit, or computation unit or console of an electromagnetic tracking system.

According to an example, for the pre-processing of the raw signals, the data processor is further configured to perform at least one of the following: filter of the raw signals, amplification of the raw signals, analogue processing and A/D (analogue-to-digital) conversion of the signals.

According to a second aspect, an electromagnetic tracking system of catheters according to claim <NUM> is provided. Advantageously, the electromagnetic tracking system is provided with reduced data communication, or with improved data via the wireless links due to the use of the wireless readout unit pre-processing the data to be transmitted via the wireless link.

In an example, for the identification of electromagnetic sources, it is provided that the identification and separation of the different signal components related to the various field generating elements is linked to how the field generator is controlled.

According to an example, upon activation, the control unit provides electromagnetic field data to the data processor of the wireless readout unit.

This advantageously allows a respective pre-processing also considering such field data.

According to an example, the wireless readout unit and the control unit (or processing unit) are configured to be synchronized so that the wireless unit can isolate the signal components from the different field generating elements.

<FIG> shows a wireless readout unit <NUM> for an electromagnetic tracking system of medical devices (for the system, see also <FIG>). The wireless readout unit <NUM> comprises a data input <NUM>, a data processor <NUM> and a data output <NUM>. The data input <NUM> is configured to receive raw signals <NUM>, indicated with a hashed arrow, from an electromagnetic sensor (not shown). The data processor <NUM> is configured to at least partly pre-process the raw signals <NUM> provided by the data input <NUM> for further transformation. The data output <NUM> is configured for data transmission of the at least partly pre-processed data to a control unit of an electromagnetic tracking system of medical devices.

The data output <NUM> provides a wireless data link <NUM>, indicated with a further hashed arrow, to a control unit (not further shown) of an electromagnetic tracking system of medical devices. The wireless link may also be provided to a processing unit or console.

<FIG> shows an example of a medical device <NUM> for electromagnetic tracking. The device comprises at least a body portion <NUM> and an electromagnetic tracking sensor <NUM>. Further, at least one example of the wireless readout unit <NUM> according to one of the above-mentioned, and below-mentioned, examples is provided. The electromagnetic tracking sensor <NUM> is configured to measure an intensity of an electromagnetic field generated by a field generator (see also <FIG>) of an electromagnetic tracking system of medical devices. The electromagnetic tracking sensor <NUM> is fixedly attached to a determination part of the medical device <NUM>. The wireless readout unit <NUM> is at least temporarily attached to the body portion <NUM>.

Before further describing the wireless readout unit <NUM> and the provided pre-processing of the raw signals, it is briefly referred to the medical device <NUM>.

The medical device <NUM> is provided for interventional or diagnostic tasks, i.e. to perform a medical function. The electromagnetic tracking is an addition to the medical device and used to monitor the position and possibly orientation of the medical device or of a portion of the medical device.

In an example, for the state information of the device, it is provided that the electromagnetic tracking system is provided with an additional two-way communication with a device, which device can be used to implement for example buttons or status LEDs. The wireless link may be able to relay this information as well. This type of information may span only a few bits per device and may not require processing. It can thus be easily performed once a connection has been established.

In an example, for the integration with a device to be tracked, it is provided that the wireless readout unit is a reusable standalone device that plugs into the device to be tracked as a dongle (see also below). A connection to the sensor is provided and, if applicable, a connection to the energy source of the device to be tracked. This is particularly appealing for low cost or disposable devices and for devices that might not always require the use of tracking. For example, a catheter for cardio-vascular applications is provided. In an alternative example, the wireless readout unit is permanently integrated within the device to be tracked. This scenario is appealing for reusable medical devices that are expected to make use of the tracking functionality most of the time. For example, a tracked US (ultrasound) transducer is provided. Referring back to <FIG>, it is noted that the data input <NUM> and the data output <NUM> are not further illustrated in <FIG>, but are of course provided.

In <FIG>, an antenna symbol <NUM> indicates the provided wireless data link <NUM> to a control unit.

The wireless readout unit <NUM> is locally performing at least some of the functions of a control unit. In an example, the wireless readout unit sends the results to the control unit for the triangulation of the device location. In another example, the triangulation of the device location is provided at least partly by the wireless readout unit.

In an example, for the wireless link <NUM>, it is provided that the wireless link allows real time operation and supports tracking multiple devices simultaneously. In addition, to limit interference with/from other devices, in an example, dedicated wireless channels in an operational theatre (hospital) environment are used. The ability of locally identifying and separating the signal components related to the different field generating elements (coils) and extracting features from these components, can significantly reduce the bandwidth and synchronization requirements of the radio, i.e., wireless, link. It is also possible to provide the wireless link as a temporal link, which sends data only in predetermined timeslots. For example, feature extraction is locally performed and the radio (wireless link) transmits only the features that are calculated for each localization event (frame) that will then be used to determine the location of the sensor at the time of calculation. This may offer further improved reliability of the tracking system.

In an example, the whole processing and communication chain has a predictable and sufficiently low latency so that it would allow for proper hand-eye coordination required for the application of this example during medical interventions.

With reference to <FIG>, in the following, the data processor <NUM> is further described, referring to the illustration of <FIG> concerning the data processor <NUM>.

For the pre-processing of the raw signals <NUM>, the data processor <NUM> is configured to perform identification and/or separation of different signal components induced by different field emitting elements of the field generator, and extraction of signal components or signal parameters that can be used for triangulation and, optionally, at least one of the group of filtering of the raw signals, amplification of the raw signals, analogue processing and analogue-to-digital conversion of the signals.

According to an example, shown in <FIG> as separate options, that can be used individually or in combination of various kinds, the data processor <NUM> comprises an amplification and/or filtering segment <NUM>. Further, an analogue-digital conversion segment <NUM> may be provided. Still further, an identification segment <NUM> for identifying electromagnetic sources and their respective ID is provided. Further, a feature extraction segment <NUM> is provided. Still further, a radio, i.e. wireless data link segment <NUM> indicates the respective conversion of the data for the wireless link <NUM>.

The segments can be provided as sub-portions of a common processor, or as individual circuits. In an example, the wireless readout unit takes over from the control unit of an electromagnetic tracking system (shown in <FIG>) some of the functionality, for example some of its most basic functionality. As indicated above, the wireless control unit may be able to perform :.

In an example, for the amplification and filtering it is provided that the signal from the sensor is filtered to remove unwanted noise/interference and then amplified. For example, the signal is digitalized for a more generalized processing, but in another example, an analogue-to-digital conversion is provided.

In a further example, indicated in <FIG> as an option, the wireless readout unit <NUM> further comprises a local energy source <NUM>. The energy source is configured to supply electric energy to the wireless readout unit <NUM>.

In an example, the wireless readout unit <NUM> is supplied with electric energy by an energy source of a medical device that is to be tracked, i.e. the wireless readout unit <NUM> receives power from an existing power source of the medical device it is attached to, e.g. the same power source that powers an ultrasound probe or power from an RF (radio frequency) generator in an ablation catheter.

In an example, for the energy source, it is provided a battery that is part of the wireless readout unit.

In an alternative example, a connection to the medical device to be tracked is provided, for example, if this is an electrically powered medical device such as an ultrasound transducer, the wireless readout unit could be configured to be supplied of energy by the medical device itself. Another example provides a combination of a wireless readout unit containing a battery, but that is also using an external power source if connected to a powered device.

In another example, the data processor is further configured to determine a change of the raw signals in relation to a given threshold, and the data transmission is only activated in case the change is above the threshold.

<FIG> shows an electromagnetic system <NUM> of medical devices. The system comprises a field generator <NUM> for generating an electromagnetic field with a known spatial distribution in a region of interest. The electromagnetic field is indicated with lines <NUM>. Further, a control unit <NUM> is provided. Still further, at least one example of the medical device <NUM> for electromagnetic tracking according to one of the above-mentioned examples is provided. The control unit <NUM> is configured to control the generation of the electromagnetic field by the field generator <NUM>, and to receive signals from the wireless readout unit <NUM>.

The communication via the wireless data link <NUM> is indicated with two antenna symbols <NUM> and respective data wave lines <NUM>.

The field generator <NUM> may comprise a plurality of coils <NUM> that can generate different electromagnetic field segments to allow a tracking of the electromagnetic sensor <NUM> in a spatial manner.

An output arrow <NUM> of the control unit <NUM> indicates the result of the spatial tracking of the electromagnetic sensor <NUM> of the medical device <NUM>.

It must be noted that the field generator <NUM> is schematically shown with a square box enclosing the plurality of coils <NUM> for illustration purposes only. Of course, the coils <NUM> may be distributed within the space, in which the electromagnetic tracking takes place.

Hence, in an example, the field generator comprises a set of coils arranged in different positions and orientations, as indicated by the coils <NUM> in <FIG>. The field generator <NUM> thus generates an electromagnetic (EM) field with a known, and often calibrated, spatial distribution in the region of interest. According to the invention, the medical device is catheter equipped with the electromagnetic sensor <NUM>, e.g. a simple coil that can measure the intensity of the electromagnetic field generated by the field generator. This measure, i.e. this so-to-speak raw signal, or raw data, is then interpreted together with the knowledge of the spatial distribution of the generated field in order to estimate the coordinates and orientation of the electromagnetic sensor and therefore of the device, in which the sensor is embedded (or typically of a part of the device that is particularly relevant, such as the tip of a catheter).

In an example, the control unit <NUM> is able to interpret the information packets received by the wireless readout unit(s) <NUM> in order to perform location triangulation.

The control unit <NUM> is configured to perform (calculate) a triangulation for determining a location of the electromagnetic tracking sensor of the medical device.

In an example, more than one medical device are provided, for example two, three, four, five, six, seven, eight, nine or ten medical devices, or more than ten medical devices.

For the identification of electromagnetic sources within the wireless readout element, it is provided that the identification and separation of the different signal components related to the various field generating elements is linked to how the field generator is controlled.

In an example, for the feature extraction it is provided that, in order to limit the bandwidth requirement of the wireless link, as indicated above, the wireless readout unit does not send raw data from the sensor to the control unit, but extracts only the relevant features that should be used for the triangulation of the location. An example of these features is the signal power received from the various coils of the field generator.

In an example, the control unit calculates coordinates based on the sensor data. The control unit also regulates, i.e. controls, the generation of the electromagnetic field, which provides the basis for the electromagnetic tracking system <NUM> since the electromagnetic field causes the electromagnetic sensor <NUM> to provide the raw signals. The control unit <NUM> can also be referred to as a processing unit, or main processing unit.

In an example, feature extraction is performed after the identification of the signal components so that the wireless readout unit <NUM> can create a packet of information containing all the features correctly related to the various electromagnetic sources for a given localization frame. This packet could include a frame number (or a time-stamp). Following this approach, the control unit <NUM> can always calculate a proper device location for each information packet correctly received (all the information required is part of a single packet in an example) and it will be able to identify missing packets.

According to an example, provided as an option, upon activation, the control unit <NUM> provides electromagnetic field data to the data processor <NUM> of the wireless readout unit <NUM> (not further shown in detail in <FIG>).

In a further option, the wireless link <NUM> is configured as a temporal link connecting the wireless readout unit <NUM> and the control unit <NUM> in predetermined timeslots.

In an example, the wireless readout unit is provided as a detachable dongle <NUM> to be temporarily attached to a medical device.

<FIG> shows an example of the medical device <NUM> in form of a catheter <NUM>. The catheter <NUM> has an elongate body <NUM> and a grip portion <NUM>. The electromagnetic tracking sensor <NUM> is arranged at a distal end portion <NUM> of the elongate body <NUM>. The wireless readout unit <NUM> is attached to the grip portion <NUM>.

For example, an interface <NUM> is provided to temporarily attach the wireless readout unit <NUM> to the body portion <NUM> of the medical device. For example, the grip portion <NUM> can be considered as a body portion.

<FIG> shows the state, in which the medical device <NUM> is about to be connected to the dongle <NUM>. <FIG> shows the state, in which the dongle <NUM> is connected to the medical device via the interface <NUM>. Radiation waves shown in hashed lines <NUM> indicate hence the functioning of the electromagnetic tracking, once the dongle is attached.

This allows the use of a small number of dongles, for example one or more dongles, to a large number of devices that can then be tracked by electromagnetic tracking. This may be of advantage for disposable devices. The dongle can be used for multiple interventions, while the devices may be disposed after every use.

<FIG> shows a further example of the medical device <NUM> in form of an ultrasound probe <NUM> in a schematic setup. The ultrasound probe <NUM> has a transducer head portion <NUM> and the electromagnetic tracking sensor <NUM> and the wireless readout unit <NUM> are arranged at the head portion <NUM>. The head portion <NUM> may also comprise a handle (sub-) portion, or sub-portion <NUM>, and the electromagnetic tracking sensor <NUM> is attached to the ultrasound probe <NUM>. For example, the wireless readout unit <NUM> and the electromagnetic tracking sensor <NUM> can be provided in the front head portion and the wireless readout unit <NUM> can be arranged within the handle or grip sub-portion. In an example, the wireless readout unit <NUM> and the electromagnetic tracking sensor <NUM> are attached to different locations, as long as the device is sufficiently rigid.

The ultrasound probe <NUM> can be operated by a separate or external energy supply, as indicated with cable <NUM>, but may also be provided with an energy storage within the ultrasound probe <NUM>, i.e. without the cable connection <NUM> and hence with an integrated energy supply. Hence, an energy or power supply <NUM> of the ultrasound probe can also be used for operating the wireless readout unit <NUM>.

<FIG> shows an example of a method <NUM> for tracking of medical devices. The following steps are provided: In a first step <NUM>, also referred to as step a), an electromagnetic field is generated. In a second step <NUM>, also referred to as step b), an intensity of the electromagnetic field is measured by a sensor attached to a predetermined point of a medical device, and raw signals are provided to a wireless readout unit that is at least temporarily attached to the medical device. In a third step <NUM>, also referred to as step c), the raw signals are pre-processed by the wireless readout unit. In a fourth step <NUM>, also referred to as step d), the pre-processed data is transmitted to a control unit of an electromagnetic tracking system by a wireless data link. In a fifth step <NUM>, also referred to as step e), a spatial position and/or spatial orientation of the predetermined point of the medical device is determined. Hence, the medical device can be tracked in an improved manner.

Claim 1:
A catheter (<NUM>) for an electromagnetic tracking system (<NUM>) comprising a control unit (<NUM>) configured to perform triangulation, the catheter comprising:
- an elongated body (<NUM>) and a grip portion (<NUM>) ;
- an electromagnetic tracking sensor (<NUM>) arranged at a distal end portion of the elongate body and configured to measure an intensity of an electromagnetic field generated by a field generator; and
- a wireless readout unit (<NUM>) at least temporarily attached to the grip portion and comprising a data input (<NUM>), a data processor (<NUM>), and a data output (<NUM>);
wherein the data input is configured to receive raw signals (<NUM>) from the electromagnetic tracking sensor;
wherein the data processor is configured to at least partly pre-process the raw signals provided by the data input by performing identification and/or separation of different signal components induced by different field emitting elements of a field generator and by performing extraction of different signal components that are needed by the control unit to perform triangulation;
- wherein the data output is configured to provide a wireless data link (<NUM>) to the control unit of the electromagnetic tracking system of the catheter and is configured for data transmission of the at least partly pre-processed data.