WO2022100925A1 - Method and system for ascertaining the rotational orientation of an electrode implanted in a patient - Google Patents

Abstract

A first aspect of the invention relates to a method for ascertaining the rotational orientation of at least one electrode (10) implanted in the body of a patient, said electrode (10) being designed to electrically stimulate a tissue area of the patient. The method has the steps of: generating at least one electric pulse by means of a stimulator, said electric pulse being emitted via the electrode (10) (S1); measuring at least one field distribution using a sensor system (S2); and determining the rotational orientation of the at least one electrode (10) relative to the body of the patient using the measured field distribution (S3). Another aspect of the invention relates to a system for determining the rotational orientation of at least one electrode (10) implanted in the body of a patient, said electrode (10) being designed to electrically stimulate a tissue area of the patient, comprising: a stimulator which is designed to generate an electric pulse on the at least one electrode (10); a sensor system for measuring a field distribution; and a processor (20) which is designed to generate a pulse program and to receive field distribution data from the sensor system, wherein the processor (20) models the rotational orientation of the at least one electrode (10) by means of a computer-implemented algorithm using the field distribution data.

Description

Method and system for determining the rotational orientation of an electrode implanted in a patient

The invention relates to a method for determining the rotational orientation of an electrode implanted in a patient's body according to the preamble of claim 1. The invention also relates to a system for determining the rotational orientation of an electrode implanted in a patient's body according to the preamble of claim 14. Finally, the Invention a use of the system to support diagnosis and / or therapy of movement disorders claim 16. Particular configurations are the subject of claims 2 to 13 and the subject of claim 15.

Deep brain stimulation (DBS or DBS) is a surgical procedure used to treat a variety of neurological movement disorders such as Parkinson's disease, tremor, or dystonia. Many new indications (including epilepsy, dementia, psychiatric disorders) are currently being researched. Currently, more than 200,000 patients worldwide are treated with DBS each year. The treatment technique involves the implantation of at least one electrode in a specific area of the patient's brain, where it emits electrical impulses in order to stimulate the relevant tissue. The stimulation is typically regulated via a likewise implanted stimulator, which is often inserted under the collarbone or the costal arch and in addition to the power supply, programming of the stimulation parameters is also possible.

Due to the size of the electrodes and deviations in their implantation, it can happen that the pulses emitted not only stimulate the desired target region, but also the surrounding tissue, which can lead to undesirable side effects. In order to solve this problem, systems have been developed in recent years that allow more precise stimulation of the target area. For example, so-called directional systems have been developed in which individual, individually controllable contacts are used, which only emit impulses in a defined direction. On the one hand, this makes it possible to improve the local precision of the stimulation and, on the other hand, to use a low impulse strength compared to non-directional stimulation systems, because the electrode no longer emits its impulses in all directions, but confines them to the desired area.

In order to be able to ensure that an electrode has been implanted correctly, or to check whether its position in the brain might have changed over time, it is important to know as much information as possible about the position of the electrode of the implanted electrodes, i.e both the localization and the rotational orientation in order to carry out corrective interventions in case of doubt. A rotational orientation is to be understood as meaning the spatial orientation of the electrode in the tissue, with the orientation describing in particular the spatial relationship of the direction of a directed stimulation to the surrounding tissue area. For example, the rotational orientation of an otherwise rotationally symmetrical electrode can be defined by the direction in which a directional impulse can be emitted. In the case of a rod or cable electrode, the rotational orientation can be described more generally by the direction of a vector extending outward perpendicular to the long axis of the electrode.

Various methods are known from the prior art, with the aid of which the position of an electrode implanted in the brain can be determined. For example, WO 2017/040573 A1 shows a method for determining a rotational orientation of a deep brain stimulation electrode. Accordingly, the rotational orientation of the electrode is determined using a comparison of image data of a marker connected to the electrode with image data of a template of the electrode. The image data of the marker, also referred to as “CT marker”, are usually obtained using X-ray-based methods or CT methods. EP 3 376 960 A1 shows a method for determining the rotational orientation of a deep brain stimulation electrode in a three-dimensional image. According to the method taught there, rotation image data describing two-dimensional medical images of an anatomical structure and the electrode, as well as tomographic image data describing a set of tomographic medical images of the anatomical structure, are read into a processor. Using the image data obtained in this way, the processor determines and describes the rotational orientation of the electrode to the reference system of the tomographic image data. Both the rotational image data and the tomographic image data are obtained using X-rays.

The first disadvantage of the current methods is that the imaging methods on which they are based deliver blurry and sometimes imprecise results, which makes it difficult to precisely determine the rotational orientation of the electrode. The procedures often have to be repeated several times in order to be able to make an exact statement about the rotational orientation. In addition, known methods use X-rays or CT or MRT methods, which leads to a high level of radiation exposure for the patient and can therefore result in some serious tissue damage in the patient. The number of possible measurements is already limited by the health risk associated with the measurement method. Long-term studies to analyze displacements or rotations of the electrodes, which can occur over time, cannot therefore be carried out using conventional measurement methods without considerable accompanying risks.

The invention is therefore based on the object of providing a method with which the rotational orientation of an electrode implanted in a patient can be determined with greater accuracy than in the prior art. The procedure should also be gentle on the patient and, in particular, minimize exposure to radiation. Furthermore, the method should also be simple and uncomplicated to carry out. A further object is to provide a system for implementing the method.

The object is achieved according to the invention with a method for determining a rotational orientation of at least one electrode implanted in the body of a patient according to patent claim 1 .

The method according to the invention for determining a rotational orientation of at least one electrode implanted in the body of a patient, the electrode being set up for electrical stimulation of a tissue area of the patient, comprises the steps:

- generating at least one electrical impulse by a stimulator, the electrical impulse being delivered via the electrode; measuring at least one field distribution by means of a sensor system; and

Determining the rotational orientation of the at least one electrode relative to the patient's body using the at least one measured field distribution.

For the purposes of this disclosure, the terms “orientation”, “rotational orientation” and “rotational orientation” are used interchangeably unless the context dictates otherwise. In addition, the terms "user" and "personnel" within the meaning of this disclosure are also to be understood as synonymous and describe - unless otherwise stated - one or more technically and/or medically trained persons who are able to use the present method or the appropriate system to use. Finally, the terms “set up” and “configured” are also used synonymously within the meaning of this application and describe the suitability of a feature or a feature combination to fulfill a specific purpose.

Specifically, the rotational orientation is to be understood as meaning the spatial orientation of the electrode in the patient's tissue, the orientation describing in particular the spatial relationship of the direction of a directed stimulation by the electrode to the surrounding tissue area. In addition to the rotational orientation, position information of the electrode can also include a specific localization of the electrode in the body in relation to the surrounding tissue in the patient (without considering the direction of stimulation). Finally, in addition to its rotational orientation and localization, it is also possible to determine the position of the electrode, i.e. its spatial extent in an x/y/z system. A position determination that is as exact as possible (i.e. position information that is as complete as possible) therefore includes knowledge of the rotational orientation, the localization and the position of the electrode.

The method according to the invention is particularly suitable for determining the rotational orientation of a directional electrode implanted in the patient's body. A directional electrode is an electrode that can be used to emit an electrical impulse in a specific direction instead of omnidirectionally. The directional electrodes, whose rotational orientation can be determined using the method according to the invention, are preferably rod electrodes or lead electrodes with at least one segmented contact.

In the step of generating the at least one electrical impulse by the stimulator, the electrode is neurosurgically implanted in the brain and is stimulated via a separate subcutaneously implanted impulse generator with control unit. The pulse generator is connected to the electrode via a cable laid under the skin. The control unit is controlled in turn, preferably wirelessly from outside, ie for example by a corresponding user, with settings being able to be made on the controller.

Measuring a field distribution by means of a sensor is to be understood as a step in which the field strengths or field densities of a respective field - for example a magnetic field or an electric field - are determined at different locations or points in a three-dimensional space (also referred to as spatial points). In concrete terms, a strength and a direction can be assigned to each point in space as a vector quantity.

Part of the position information of the electrode is already known through the step of determining the rotational orientation of the at least one implanted electrode relative to the patient's body. In addition, conclusions can be drawn about the localization and the spatial position of the electrode based on the rotational orientation. This complete determination of the position of the electrode finally makes it possible to determine which tissue areas of the patient are actually being stimulated by the electrode. These conclusions are not possible solely on the basis of a known location of the electrode, because this does not yet clearly indicate at which point on the electrode the stimulation takes place, i.e. where electrical impulses are emitted.

Such a method, which can be used in particular as a measurement method to accompany independent therapeutic methods, has the advantageous effect that it does not require any external radiation supply (cf. X-ray or CT methods) or magnetic resonance steps (cf. MRT). Instead, the method according to the invention only provides electrical stimulation of the implanted electrode before the measurement of the field distribution. The stimulation differs insignificantly from the usual stimulation patterns provided for treatment purposes in terms of duration, strength and other properties of the selected impulses and is therefore hardly noticeable to the patient, but above all it is not harmful. Thus, the risks of long-term damage can be drastically reduced using the proposed method.

In order to determine at which location and in which directions the implanted (directional) electrode can stimulate, it is necessary to know not only its localization in the patient's tissue but also its spatial position and its rotational orientation. Current methods often use a physical marker of the electrode known as a CT marker or “radio-opaque marker”, which can be visualized using a CT. Based on the orientation of the marker, conclusions can be drawn about the orientation of the electrode. The method according to the invention eliminates the need for the CT marker because the rotational orientation of the electrode is based solely on its actual stimulation pattern can be determined. By doing without the CT marker, smaller electrodes, which are therefore more suitable for implantation in the brain, can be used in DBS.

In the method it can be provided that the field distribution is a distribution of a magnetic field generated by the at least one electrical pulse, the field distribution of the magnetic field being measured by means of a magnetic field sensor system. The magnetic field is measured in the SI unit Tesla (T), whereby the distribution of the magnetic field - which can also be described in the form of different magnetic field densities - of the magnetic field generated with the preferred method is usually in the pT to nT range.

Provision can also be made for the field distribution to be a distribution of an electrical voltage field generated by the at least one electrical pulse, with the field distribution of the voltage field being measured using a voltage sensor system. The field, known as the voltage field, is made up of various electrical signals (potential differences). The electric field strength (E) is used to determine the electric field. For the purpose of this disclosure, the terms “voltage field” and “electrical field” are used synonymously, as long as nothing to the contrary results from the specific context.

In particular, it is advantageously provided that a magnetic field distribution is measured, with the magnetic field measurements preferably being carried out outside the patient's head. This allows the rotational orientation of the electrode to be determined in a simple manner when the electrode generates a magnetic field as a result of stimulation. The field distribution of the magnetic field corresponds to the pulses emitted during the stimulation, so that the measured magnetic field distribution can be used to determine the direction in which the pulses were emitted by the electrode. From this, in turn, conclusions can be drawn about the position of the contacts and thus about the rotational orientation of the electrode.

Analogously to this, the field distribution of an electric field generated by the stimulation can also be measured instead of or in parallel to the field distribution of the magnetic field. The field distribution of the electrical field corresponds to the pulses emitted during the stimulation, so that the measured electrical field distribution can be used to determine the direction in which the pulses were emitted by the electrode. From this, conclusions can also be drawn about the position of the contacts and thus about the rotational orientation of the electrode.

It is also conceivable that the method also includes the step: - Creation of an impulse program in advance of generating the at least one electrical impulse, the impulse program comprising a large number of variable impulse parameters selected from the group comprising electrode configuration, specifically activatable electrode contacts, electrode position, impulse amplitude, impulse duration and impulse frequency.

A previously defined pulse program makes it possible to carry out the best possible stimulation for measuring the field distribution in a reliable and reproducible manner. In addition, the pulse program can be changed depending on various accompanying factors such as the patient's characteristics, the type of stimulation, the type of electrode, etc., which always ensures that the stimulation for generating the magnetic field or the electric field takes place under conditions which are optimal for the measurement or for the patient.

An electrode configuration is preferably to be understood as meaning the configuration of the electrode with regard to its possible pulse pattern. Thus, the electrode configuration can include a monopolar pulse and a bipolar pulse, wherein the at least one electrical pulse according to the preferred method is in particular a bipolar pulse. Tests have shown that bipolar stimulation results in a more focused spatial distribution of the generated magnetic or electric field compared to monopolar stimulation, which in turn leads to a better resolution of the field distribution and thus allows a more accurate determination of the rotational orientation of the lead. In contrast, monopolar stimulation has the advantage that stronger fields can be generated, which can be better detected. A combination of monopolar and bipolar stimulation can therefore lead to optimal measurement results, which in turn makes it considerably easier to evaluate the measurement results.

Advantageously, the method can further include the steps:

- changing at least one pulse parameter of the pulse program;

- Re-measure the field distribution.

According to a preferred embodiment, the two steps “changing at least one pulse parameter of the pulse program” and “re-measuring the field distribution” are carried out in the specified order after the step “measuring a field distribution using a sensor system”, but before the step “determining the rotational orientation of the at least an electrode relative to the patient's body based on the measured field distribution". The two steps can be repeated as often as you like. A change in the field distribution is measured as a function of the change in the at least one pulse parameter. As a result, the accuracy of the measurement method can be additionally increased. Electrodes implanted in patient tissue usually have contacts through which they deliver their electrical impulses for stimulation. Implanted rod or cable electrodes are characterized in that they have a cylindrical outer surface on which their contacts are arranged. In the case of rod electrodes or cable electrodes that are set up for directed stimulation, the contacts can be segmented in such a way that they only partially enclose or run around the lateral surface. For example, the electrodes can comprise at least three partially circumferential segmented contacts, each of which runs around less than 360°, preferably approximately 120°, of the circumference of the cylindrical outer surface of the electrode. However, under certain circumstances, the different segments of the electrode contacts can be resolved to different extents with a specific stimulation pattern. By changing the pulse parameters, the optimal stimulation program can be selected and used for each electrode contact, which increases the spatial resolution of the field distribution. According to a preferred embodiment of the method, it can be provided that the step of changing a pulse parameter of the pulse program is carried out on a processor.

According to a further embodiment, it can be provided that the method also includes the steps:

- Transmission of field distribution data, which correspond to the measured field distribution, to a processor, the processor being set up or suitable for executing a computer-implemented algorithm which models the rotational orientation of the at least one electrode on the basis of the field distribution data;

- executing the computer-implemented algorithm by the processor;

- Modeling of the rotational orientation based on the field distribution data. wherein the determination of the rotational orientation of the at least one electrode relative to the patient's body is based on the rotational orientation modeled by the computer-implemented algorithm. The data corresponding to the field distribution can be transmitted via a cable and/or wirelessly.

According to an advantageous embodiment, the steps "transferring field distribution data to a processor", "executing the computer-implemented algorithm by the processor" and "modeling the rotational orientation using the field distribution data" are carried out in the order given, but after the step "measuring a field distribution using a Sensors” and before the step “determination of the rotational orientation of the at least one electrode relative to the patient's body based on the measured field distribution”. The algorithm includes, among other things, a localization algorithm in which the origin of the magnetic or electric field, together with its localization and orientation within the patient's head, is calculated on the basis of the measured field distribution. Various localization algorithms can be used to localize the origin, such as the "dipole fitting approach" and MNE ("minimum norm estimates"). ), MUSIC (multiple signal classification), LORETA (low-resolution brain electromagnetic tomography), various as "Beamformer" English, loosely translated as "beam shaper") designated methods, or other solution methods. It is also conceivable that a deviation from the determined localization and orientation data is specified in order to determine the accuracy of the measurement. For this purpose, the processor can calculate a mean square deviation, for example.

Based on the algorithmically calculated data points, the processor models a rotational orientation of the electrode. A user of the method can then display this modeled rotational orientation via a display device such as a screen or a monitor.

In particular, it is provided that the method is a computer-implemented method. In addition, it is conceivable that not only partial steps of the method, but the entire method can be controlled via the processor. In this case, the processor is preferably a logic unit which is designed to automatically execute or advance the algorithm after appropriate programming. The processor can include a CPU and in particular be part of a computer or a comparable computing system.

According to an advantageous development, it is provided that the at least one electrode is implanted in the patient's brain, with the electrode being set up in particular for deep brain stimulation. Systems used in deep brain stimulation often include a battery powered control element that is placed in the chest muscles or upper abdomen. The stimulating electrode or electrodes are inserted through small holes in the skullcap into the target region of the left and/or right hemisphere basal ganglia and must be appropriately designed to remain in biological tissue for a long time. The at least one electrode is preferably a rod electrode or a cable electrode, with the electrode being set up or suitable in particular for directed stimulation. With the help of directed electrodes, desired tissue areas can be stimulated in a targeted and precise manner. A directed rod electrode or a directed cable electrode has a cylindrical outer surface. Such electrodes can, for example, comprise at least three partially circumferential segmented contacts, each of which surrounds less than 360°, preferably approximately 120°, of the circumference of the cylindrical outer surface of the electrode. Preferably, an electrode can be provided which has eight contacts, with two of the eight contacts encircling the electrode as unidirectional ring contacts and six of the eight contacts being designed as partially encircling segmented contacts.

aufweisen. Bevorzugt kommen bei dem offenbarten Verfahren jedoch Sensoren zum Einsatz, die ungekühlt, d.h. bei Raumtemperaturen, einsetzbar sind und die außerdem keinen magnetisch oder elektrisch abgeschirmten Raum benötigen. Generell sind fast alle Sensoren zur Verwendung bei dem offenbarten Verfahren geeignet, mit denen sich die Feldverteilung eines Magnetfelds messen lässt, wie z.B. Fluxgate- Magnetometer, OPM („Optically pumped magnetometers", engl., frei übersetzt als „optisch beladene Magnetometer“), „surface acoustic wave sensors" (engl., frei übersetzt als „Akustische Oberflächenwellensensoren“) etc. According to a preferred embodiment of the method, it is provided that the magnetic field sensor system comprises at least one magnetic field sensor, the magnetic field sensor system comprising cooled MEG sensors and/or uncooled MEG sensors, and the cooled MEG sensors preferably being cooled with liquid helium. The MEG sensors can be SQU ID sensors, for example. SQU ID sensors are suitable for measuring the magnetic field generated during deep brain stimulation because they have a noise spectral density of around 3

exhibit. In the disclosed method, however, preference is given to using sensors which can be used uncooled, ie at room temperatures, and which also do not require a magnetically or electrically shielded space. In general, almost all sensors are suitable for use in the disclosed method, with which the field distribution of a magnetic field can be measured, such as fluxgate magnetometers, OPM ("optically pumped magnetometers", loosely translated as "optically loaded magnetometers"), "surface acoustic wave sensors" (English, loosely translated as "surface acoustic wave sensors") etc.

It can be provided that the magnetic field generated by the at least one electrical pulse is measured outside of the patient's head. Provision is also made in particular for the measurement of the electrical field generated by the at least one electrical pulse to take place outside of the patient's head. This allows the field distribution to be determined in a simple manner. An operative step is not necessary.

The voltage sensor system for measuring the electric field can in particular include EEG sensors. According to a preferred embodiment of the method, the EEG sensors measure a field distribution in the form of brain waves.

In particular, it can be provided that the method is a computer-implemented medical method, the method preferably being a computer-implemented one is a medical procedure to support the diagnosis and/or therapy of movement disorders. It is conceivable, for example, that long-term studies can be carried out using the disclosed method in order to examine displacements or rotations of electrodes implanted in the brain that occur over time without having to expose the patient to radiation. In addition, with the method there is the possibility, if necessary, to check in an inpatient setting whether the implanted electrodes are correctly implanted and aligned in a DBS patient. This can increase the efficiency of DBS -based treatment.

According to a further aspect of the invention, a system for determining a rotational orientation of at least one electrode implanted in the body of a patient is provided, the electrode being set up for electrical stimulation of a tissue area of the patient, comprising:

- a stimulator which is set up to generate an electrical pulse at the at least one electrode;

- A sensor for measuring a field distribution; and

- A processor, the processor is set up or suitable for creating a pulse program and which is set up or suitable for receiving field distribution data from the sensor system, the processor using a computer-implemented algorithm based on the field distribution data to model the rotational orientation of the at least one electrode.

It can also be provided that the sensor system of the system includes a magnetic field sensor system and/or a voltage sensor system. It is provided in particular that the magnetic field sensor system comprises at least one magnetic field sensor or that the voltage sensor system comprises at least one voltage sensor for measuring an electric field. According to an advantageous development of the system, the magnetic field sensors and/or the voltage sensors can be arranged on a sensor cap, which is designed such that the electrode can be placed at least partially on a patient's head during the method for determining the rotational orientation. According to a further embodiment, it can instead be provided that the magnetic field sensors and/or the voltage sensors are arranged on an annular sensor band. The sensor band can be attached to the patient's head (similar to a headband) for use in the method for determining the rotational orientation of the electrode.

According to a further aspect of the invention, the system can be used to support the diagnosis and/or therapy of movement disorders and others diseases treatable by deep brain stimulation. The disclosed method can be used, for example, to carry out long-term studies in order to examine displacements or rotations of electrodes implanted in the brain that occur over time. This is mainly possible because the procedure measures a field generated by stimulation - preferably magnetic or electric - and the patient therefore does not have to be exposed to radiation. In addition, with the method there is the possibility, if necessary, to check on an inpatient basis whether the implanted electrodes are correctly implanted and aligned in a DBS patient. This can increase the efficiency of the DBS-based treatment.

Further features, details and advantages of the invention result from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings.

Show it:

1 shows a flow chart of the steps of a preferred method for determining a rotational orientation of at least one electrode implanted in the body of a patient, the electrode being set up for electrical stimulation of a tissue area of the patient; a flowchart of method steps according to a second

embodiment; a flowchart of method steps according to a third

embodiment;

4 shows a flowchart of method steps according to a fourth

embodiment;

5 shows a flowchart of method steps according to a fifth

embodiment;

Figure 6a is a perspective view of an electrode suitable for implantation in a patient; and

6b shows a cross-section through an electrode suitable for implantation in a patient. 1 shows a flow chart of steps S1-S3 of the method according to the invention for determining a rotational orientation of at least one electrode 10 implanted in the body of a patient, the electrode 10 being set up for electrical stimulation of a tissue area of the patient.

In a preferred embodiment, the method includes a first step S1: generating at least one electrical impulse using a stimulator, with the electrical impulse being emitted via the electrode 10. In this step, the electrode 10 is caused, via a separate control unit, to deliver an electrical pulse at the site in the patient's body where it is implanted. The control unit is usually also implanted and can be connected to the electrode 10 via a cable connection or wirelessly. The control unit is in turn controlled from outside, for example by appropriate specialist personnel, with settings on the control unit preferably being able to be made wirelessly.

As the next step S2 it is provided that a field distribution is measured by means of a sensor system. This is to be understood as a step in which the field strength or field density is determined at different points in space. For example, a strength and a direction are assigned to each measured point in space as a vector quantity. When measuring a magnetic field, cooled MEG sensors and/or uncooled MEG sensors can be provided as sensors, the MEG sensors being in particular SQU ID sensors. In the case of measuring an electric field, this can include EEG sensors in particular, which measure the field distribution in the form of brain currents.

Finally, step S3 takes place, after which a rotational orientation of the at least one electrode 10 is determined relative to the patient's body and based on the measured field distribution. Once this step has taken place, the spatial rotational orientation of the electrode 10 in the patient's body is known. In this way, conclusions can be drawn as to which tissue areas of the patient are actually stimulated by the electrode 10 . These conclusions are not possible solely on the basis of a known localization of the electrode 10, because this does not clearly indicate at which point on the electrode 10 the stimulation takes place, i.e. electrical impulses are emitted.

Using a method as shown in FIG. 1, the rotational orientation of an electrode 10 implanted in a patient can be determined without exposing the patient to radiation exposure, which would be associated with X-ray or CT-based methods. The risks associated with MRI procedures can also be reduced by the avoid methods according to the invention. Instead, the method according to the invention provides electrical stimulation of the implanted electrode 10 prior to the measurement of the field distribution. The stimulation differs at most insignificantly from the usual stimulation patterns provided for treatment purposes with regard to duration, strength and other properties of the selected impulses and is therefore hardly noticeable for the patient. Above all, the risks of long-term damage can be drastically reduced using the proposed method.

FIG. 2 shows a flow chart of the method steps according to a second embodiment of the method. The method according to FIG. 2 differs from the method shown in FIG includes pulse parameters selected from the group comprising electrode configuration, specifically activatable electrode contacts, electrode position, pulse amplitude, pulse duration and pulse frequency.

The stimulation required for the measurement can be carried out reliably through step S1.1. Finally, a definable impulse program enables repeated stimulation with known and constant impulse and thus stimulation properties. In addition, the pulse program can be changed depending on various accompanying factors such as the patient's characteristics, the type of stimulation, the type of electrode (10), etc., which always ensures that the stimulation is used to generate the magnetic field or the electric field under optimal conditions for the patient.

The electrode configuration can include a monopolar pulse and a bipolar pulse, with the at least one electrical pulse being a bipolar pulse in particular according to the preferred method. Tests have shown that bipolar stimulation results in a focused spatial distribution of the generated magnetic or electric field compared to monopolar stimulation, which in turn leads to better resolution of the field distribution and thus enables a more precise determination of the rotational orientation of the lead. In contrast, monopolar stimulation has the advantage that stronger fields are generated with it, which can be better detected. Accordingly, a combination of monopolar and bipolar stimulation leads to optimal measurement results, which in turn makes it considerably easier to evaluate the measurement results.

In order to determine at which location and in which direction the implanted directional electrode 10 can stimulate, it is necessary to know not only its localization in the patient's tissue but also its exact position and its rotational orientation. Common Methods use a physical marker of the electrode 10 referred to as a CT marker or as a "radio-opaque marker", which can be visualized via a CT. Based on the orientation of the marker, conclusions can be drawn about the orientation of the electrode 10. The inventive This method eliminates the need for the CT marker because the orientation of the electrode 10 can be determined solely from its actual stimulation pattern.The elimination of the CT marker allows smaller electrodes 10, which are therefore more suitable for implantation in the brain, to be used in DBS.

According to the method shown in FIG. 3, a step S1.2 can also be provided, after which at least one pulse parameter of the pulse program is changed after a first measurement of the field distribution S2. The field distribution is then measured at least once more S2.1. A change in the field distribution is measured as a function of the change in the at least one pulse parameter. Steps S1, S1.2 and S2.1 can be repeated as often as desired. According to the example from FIG. 3 , it can be provided that step 1.2 is executed on a processor 20 .

Some areas or contacts of the lead may not resolve well with a particular stimulation pattern. By changing the pulse parameters, the optimum stimulation program can be selected and used for the various electrode contacts, which increases the spatial resolution of the field distribution. As a result, the accuracy of the measurement method can be additionally increased.

4 shows a flowchart of method steps according to a fourth embodiment. Accordingly, the following steps can also be provided for the method: Transmission of field distribution data, which correspond to the measured field distribution, to a processor 20, wherein the processor 20 is set up to execute a computer-implemented algorithm that uses the field distribution data to determine the rotational orientation of the at least one electrode modeled (S3.1); executing the computer-implemented algorithm by the processor 20 (S3.2); Modeling of the rotational orientation using the field distribution data (S3.3). Subsequent to the modeling step S3.3, the rotational orientation of the one electrode 10 relative to the patient's body can be determined using the rotational orientation modeled by means of the computer-implemented algorithm.

The data corresponding to the field distribution can be transmitted to the processor 20 according to step S3.1 via cable and/or wirelessly. The processor 20 is preferably a logic unit which is designed to automatically execute or advance the algorithm after appropriate programming. But he can Processor 20 include a CPU and in particular be a computer or a comparable computing system. In addition to the variant shown in FIG. 4, according to which only steps S3.2 and S3.3 are executed by the processor 20, methods are also conceivable in which further or all method steps are executed by the processor 20. As a result, parts of the method or the entire method can be automated and thus accelerated.

The algorithm of step S3.2 includes, among other things, a localization algorithm in which the origin of the magnetic or electric field, together with the localization and orientation within the patient's head, is calculated using the measured field distribution. It is also conceivable that a deviation from the determined localization and orientation data is specified in order to determine the accuracy of the measurement. This step can include various localization algorithms for the localization of the origin, such as "dipole fitting approach" (English, loosely translated as "approach to dipole approximation"), MNE ("minimum norm estimates", English, loosely translated as "estimates of the minimum norm ’), MUSIC (‘multiple signal classification’), LORETA (Jow-resolution brain electromagnetic tomography), various as Methods referred to as "Beamformer" (freely translated as "ray shaper"), or other solution methods.

For this purpose, the processor 20 can calculate a mean square deviation, for example. The processor 20 uses the algorithmically calculated data points to model a rotational orientation, as shown in step 3.3 of FIG. This modeled rotational orientation can then be displayed via a display device such as a screen.

FIG. 5 shows a flow chart of method steps according to a fifth embodiment. The method shown in FIG. 5 can be understood as a combination of the methods from FIGS. 3 and 4 and essentially includes all disclosed steps of the claimed method. The method according to the embodiment shown in FIG. 5, together with steps S1 to S3 and with all the preliminary, subsequent and intermediate steps, has proven to be particularly efficient because it links the steps described in detail with one another in such a way that the rotational orientation of the electrode implanted in the patient can be determined with particularly high accuracy. Even if all steps are used, the method is free of any radiation exposure for the patient. FIG. 6a shows a perspective view of an exemplary electrode 10 suitable for implantation in tissue (preferably the brain) of a patient. 6b shows the same electrode 10 in cross section. The electrode 10 shown is a directional electrode 10 and as such is capable of delivering electrical impulses in a specific direction rather than omnidirectionally. According to the example shown in FIGS. 6a, b, the electrode 10 is also a cable electrode 10 with a cylindrical and elongated body 12, on which eight contacts 10a, 10b and 11af are arranged in the present case. The contacts include two non-directional annular contacts 10a, 10b and six directional contacts 11af. The directional contacts 11 af are two groups (11a-c and 11df) each consisting of three partially circumferential segmented contacts, each segment of which extends approximately 120° of the circumference of the electrode 10 . Non-contact areas or portions of the electrode 10 may be made of an electrically non-conductive material. Such an electrode usually also includes an orientation marker (often a CT marker) in order to be able to understand the rotational orientation of the electrode in the respective tissue of a patient using conventional methods. According to the example shown in FIGS. 6a, b, no marker is shown, with such a structure or a structure comparable thereto no longer being required anyway for the method according to the invention.

In the case of the cable electrode 10 shown by way of example, the rotational orientation will generally be described by the direction of a vector V pointing outward perpendicular to a longitudinal axis A of the electrode 10 . The right angle at which the vector V runs to the longitudinal direction A of the electrode 10 is denoted as angle a in FIG.

The invention is not limited to one of the embodiments described above, but can be modified in many ways.

All of the features and advantages resulting from the claims, the description and the drawing, including structural details and method steps, can be essential to the invention both on their own and in a wide variety of combinations. In particular, the possible combinations of the individual method steps are not limited to the method steps shown as examples. reference list

S step

10 electrode

10a first annular contact

10b second annular contact

11 a-f segmented contacts

12 bodies

13 electrode tip

20 processor

A longitudinal axis

V vector a angle

Claims

Claims Method for determining a rotational orientation of at least one electrode (10) implanted in the body of a patient, the electrode (10) being set up for electrical stimulation of a tissue area of the patient, comprising the steps: - Generating at least one electrical impulse by a stimulator, the electrical impulse being emitted via the electrode (10) (S1); - Measuring at least one field distribution by means of a sensor system (S2); - Determining the rotational orientation of the at least one electrode (10) relative to the patient's body using the at least one measured field distribution (S3). Method according to Claim 1, characterized in that the field distribution is a distribution of a magnetic field generated by the at least one electrical pulse, the field distribution of the magnetic field being measured by means of a magnetic field sensor system, and/or that the field distribution is a distribution of a field generated by the at least one electrical pulse generated field of electrical voltages, the distribution of the electrical voltages being measured by means of a voltage sensor. Method according to one of Claims 1 or 2, characterized in that the method also comprises the step: - Creation of an impulse program in advance of generating the at least one electrical impulse, the impulse program comprising a large number of variable impulse parameters selected from the group comprising electrode configuration, specifically activatable electrode contacts, electrode position, impulse amplitude, impulse duration and impulse frequency (S1.1). A method according to claim 3, characterized in that the electrode configuration comprises a monopolar pulse and a bipolar pulse. Method according to one of claims 3 or 4, characterized in that the method further comprises the steps: - changing at least one pulse parameter of the pulse program (S1.2); - renewed measurement of the field distribution (S2.1). Method according to any one of the preceding claims, characterized in that the method also comprises the steps of: - Transmission of field distribution data, which correspond to the measured field distribution, to a processor, the processor being set up to execute a computer-implemented algorithm which models the rotational orientation of the at least one electrode (10) using the field distribution data (S3.1); - executing the computer-implemented algorithm by the processor (S3.2); - modeling of the rotational orientation based on the field distribution data (S3.3); wherein the rotational orientation of the at least one electrode (10) relative to the patient's body is determined using the rotational orientation modeled by the computer-implemented algorithm. Method according to one of the preceding claims, characterized in that the at least one electrode (10) is implanted in the patient's brain, the electrode (10) being set up in particular for deep brain stimulation. Method according to one of the preceding claims, characterized in that the at least one electrode (10) is in particular a rod electrode or a cable electrode, the electrode (10) being set up for directed stimulation and the directed electrode (10) having at least three segmented contacts ( 11 a-f). Method according to one of the preceding claims 2 to 8, characterized in that the magnetic field sensor system comprises at least one magnetic field sensor, the magnetic field sensor system comprising cooled MEG sensors and/or uncooled MEG sensors, the cooled MEG sensors being cooled in particular with liquid helium. Method according to one of Claims 2 to 9, characterized in that the voltage sensor system comprises EEG sensors. Method according to Claim 10, characterized in that the EEG sensors measure a field distribution in the form of brain waves. Method according to one of the preceding claims, characterized in that the method is a computer-implemented medical method, the method in particular a computer-implemented medical method for Supporting the diagnosis and/or therapy of movement disorders and other diseases that can be treated with deep brain stimulation. 13. System for using a method according to any one of the preceding claims, comprising: - a stimulator which is set up to generate an electrical pulse at the at least one electrode (10); - A sensor for measuring a field distribution; and - a processor (20) which is set up to create a pulse program and which is set up to receive field distribution data from the sensor system, the processor (20) using a computer-implemented algorithm based on the field distribution data to determine the rotational orientation of the at least one electrode (10 ) modeled. 14. System according to claim 13, characterized in that the sensor system comprises a magnetic field sensor system and/or a voltage sensor system. 15. System according to claim 14, characterized in that the magnetic field sensor system comprises at least one magnetic field sensor and that the voltage sensor system comprises at least one sensor for measuring an electric field. 16. System according to claim 15, characterized in that the magnetic field sensors and/or the voltage sensors are arranged on a sensor cap, the sensor cap being suitable for being placed on the patient's head. 17. System according to claim 15, characterized in that the magnetic field sensors and/or the tension sensors are arranged on a ring-shaped sensor strip, the sensor strip being suitable for being attached to the patient's head. 18. Use of the system according to any one of the preceding claims to support the diagnosis and/or therapy of movement disorders and other diseases that can be treated with deep brain stimulation.