DE102019209333A1 - Method for determining a local tissue type of body tissue and medical system for carrying out such a method - Google Patents

Abstract

The invention relates to a method for determining a local tissue type of body tissue and to a medical system which is set up to carry out such a method. Use in typing body tissue.

Description

The invention relates to a method for determining a local tissue type of body tissue and to a medical system for carrying out such a method.

Such a method and such a medical system are generally known in the field of medical technology.

The well-known method, which can also be referred to as electrical impedance spectroscopy (EIS), is intended to determine a local tissue type of a body tissue. In this case, an electrical alternating voltage with a frequency that changes over time is impressed on the body tissue by means of an external electrode arranged outside the body tissue. The frequency of the alternating voltage is varied over a frequency range of, for example, 1 kHz to 1 MHz. By means of a needle placed in the body tissue and provided with another electrode, the alternating current resistance of the body tissue is measured as a function of the impressed alternating voltage, and an impedance spectrum of the body tissue is recorded in this way. The detected impedance spectrum allows a conclusion to be drawn about a local tissue type of the body tissue in the area of the second electrode, so that a statement can be made about whether it is, for example, fat, muscle or tumor tissue. The area that is relevant in terms of measurement technology - assuming an idealized assumption of homogeneous body tissue in the area of the needle - has a spherical shape extending around the further electrode. Accordingly, the generally known method provides a statement averaged over this spherical tissue section and, in this respect, not strongly local, but rather global. In order to enable the tissue type to be determined more locally, the additional electrode arranged on the needle can in principle be made as small as possible in comparison to the dimensions of the needle. However, this approach is limited by the current density that is established at the further electrode, which increases as the dimensions of the further electrode decrease. Because with increasing current density, non-linearities come into play, which can ultimately be detrimental to a reliable determination of the tissue type. This fact can only be counteracted to a limited extent by reducing the applied alternating voltage. Because with decreasing AC voltage, the sensitivity of the method to external electrical influences increases.

The object of the invention is to provide a method and a medical system of the type mentioned at the outset, each of which has advantages over the prior art and, in particular, enables the local tissue type to be determined in a locally improved manner.

This object is achieved by providing a method according to the invention with the features of claim 1 and a medical system according to the invention with the features of claim 4.

The method according to the invention for determining a local tissue type of a body tissue has the following steps: a) coupling an electrical alternating variable into the body tissue; b) Detecting a signal of an electrical voltage resulting as a function of the coupled-in alternating quantity, the electrical voltage being measured between a first electrode and a second electrode, the first electrode and the second electrode being arranged on a medical invasive component and along a longitudinal axis of the invasive component are spaced from one another by a distance, and wherein the medical invasive component is arranged in the body tissue and the longitudinal axis extends in the region of a local tissue section of the body tissue; c) Determining the local tissue type in the region of the tissue section as a function of the detected signal. The solution according to the invention enables a locally improved determination of the tissue type. For this purpose, the solution according to the invention provides in particular that the signal is recorded as a function of the voltage measured between the first electrode and the second electrode, the first electrode and the second electrode being offset from one another along the longitudinal axis of the invasive component. The solution according to the invention is based on the consideration that the voltage between the first electrode and the second electrode is primarily influenced by a current flow occurring in the area of the second electrode. As a result, compared to the prior art - with an approximately spherical shape of the metrologically detected tissue section - figuratively speaking, there is a local displacement of the metrologically detected tissue section towards the second electrode. Instead of the idealized spherical shape of the metrologically relevant tissue section, a club-shaped shape can be expected due to the solution according to the invention. In other words, the solution according to the invention can be expected to have a type of directional characteristic in the direction of the second electrode, so that the tissue type can be determined in a localized manner in an improved manner.

Step a) includes coupling in the electrical alternating variable. The electrical alternating quantity can, for example, be an alternating voltage and / or as alternating current and / or in the form of a band-limited noise signal and / or a multi-frequency signal are coupled into the body tissue. The alternating electrical quantity is preferably coupled in as an alternating voltage. Coupling can take place here with a frequency that changes over time. A range from 1 kHz to 1 MHz, for example, can be selected as the frequency range within which the alternating variable is changed over time. The alternating electrical quantity can be coupled in by means of a third electrode. The third electrode can be arranged in the body tissue or can be arranged on the outside of the body tissue.

Step b) comprises the acquisition of the signal resulting as a function of the coupled-in alternating quantity, the voltage relevant for this being measured with high resistance between the first electrode and the second electrode. Both the first electrode and the second electrode are arranged on the medical invasive component. It is provided here that the first electrode and the second electrode are spaced apart from one another in relation to the longitudinal axis of the invasive component. During the acquisition of the signal, the invasive component is arranged in the body tissue and can, in particular, be advanced along a direction of advance in the body tissue. The longitudinal axis of the invasive component is preferably oriented parallel, particularly preferably colinear, to the direction of advance. If the invasive component is to be advanced when the voltage spectrum is recorded, this preferably takes place in the distal direction. The second electrode is preferably arranged on a distal end section of the invasive component. The detected signal can in particular include a voltage spectrum and / or an impedance spectrum.

Step c) comprises determining the local tissue type as a function of the detected signal. The local tissue type can be determined either directly or indirectly on the basis of the detected signal. For example, the voltage signal can first be converted into an impedance spectrum based on fundamentally known physical laws and then the local tissue type can be determined as a function of the impedance spectrum that is now available. The determination can in particular comprise a comparison of the recorded signal with a reference signal determined for a specific tissue type. The comparison of the recorded signal with the reference signal can in particular take place on a data basis and / or with the aid of a computer. In addition, the local tissue type can be determined as a function of the coupled alternating quantity.

In an embodiment of the invention, the alternating variable is coupled in in the form of an alternating voltage and / or an alternating current and / or a band-limited noise signal and / or a multi-frequency signal. The alternating quantity is preferably coupled in in the form of the alternating voltage.

In a further embodiment of the invention, the alternating variable is coupled in with a frequency that changes over time.

The medical system according to the invention is intended to determine a local tissue type of a body tissue, to the extent that it is designed to carry out the method according to the invention and has: a coupling device that is designed to couple an electrical alternating variable into the body tissue, a medical invasive component intended to be inserted into the body tissue a first electrode and a second electrode, wherein the first electrode and the second electrode are arranged spaced apart from one another along a longitudinal axis of the invasive component, a detection device which is connected to the first electrode and the second electrode and for detecting an alternating quantity resulting as a function of the coupled-in alternating quantity Signal of an electrical voltage measured between the first electrode and the second electrode is set up, and a determination device that is used to determine the local tissue type as a function of the detected n signal is set up. The medical system according to the invention enables a locally improved determination of the tissue type.

The coupling device is set up for coupling in the electrical alternating variable. For this purpose, the coupling device can be assigned an alternating voltage and / or alternating current source and / or a noise signal source and / or a multi-frequency signal source, or the coupling device can have such a source. The coupling device can have a third electrode which can be arranged in the body tissue for coupling in the electrical alternating variable. Alternatively, the third electrode can be provided for external application to the body tissue and to that extent designed as an external electrode.

The medical invasive component is intended to be inserted into the body tissue and can in particular be designed as a catheter, cannula, needle or the like. The first electrode and the second electrode are each arranged on the invasive component and, for this purpose, can for example be glued or printed onto the invasive component in a manner known in principle. Method of applying appropriate Conductor tracks and any insulation layers, for example by means of a printing process, immersion process or in the form of vacuum coatings, are known as such in principle. The first electrode and the second electrode are arranged at a distance from one another along the longitudinal axis of the invasive component, the second electrode preferably being arranged in the region of a distal end section of the invasive component. In contrast, the first electrode is preferably arranged at a distance from the second electrode in the proximal direction. The medical invasive component is preferably provided for advancing within the body tissue along a advancing direction, the longitudinal axis preferably being oriented parallel, particularly preferably colinear, to the advancing direction. The second electrode is preferably upstream of the first electrode with respect to the direction of advance. The advance of the medical invasive component can be provided in the distal direction.

The detection device is set up to measure the signal of the electrical voltage between the first electrode and the second electrode and, for this purpose, is connected to the first electrode and the second electrode by means of signal lines suitable for this purpose. The detection device is preferably set up for high-resistance measurement of the voltage. In addition, the detection device is set up to detect the spectrum of the measured voltage resulting from the variable frequency of the coupled-in alternating quantity. In addition, the acquisition device can be set up to acquire the alternating variable coupled in by means of the coupling device. In particular, the alternating variable can be evaluated here together with the high-impedance detection of the voltage.

The determination device is used to determine the local tissue type as a function of the detected signal. For this purpose, the determination device can in particular have a memory unit in which reference signals for different tissue types can be stored in a data-based manner. The determination device can be set up for the data-based and / or computer-aided comparison of the detected signal with the said reference signals. For this purpose, the determination device can have a processor unit suitable for this purpose. The determination device can also be set up to determine the local tissue type as a function of the coupled-in alternating variable. Accordingly, in addition to the recorded signal, the coupled-in alternating quantity can also be taken into account to determine the local tissue type.

In a further embodiment of the invention, the coupling device is set up to couple the alternating variable in the form of an alternating voltage and / or an alternating current and / or a band-limited noise signal and / or a multi-frequency signal.

The coupling device is preferably set up for coupling in the alternating variable in the form of the alternating voltage.

In a further embodiment of the invention, the coupling device is set up for coupling in the alternating variable at a frequency that changes over time.

In a further embodiment of the invention, the coupling device has a third electrode which is provided for external application onto the body tissue. The third electrode can be electrically connected to an AC voltage or AC current source for generating the electrical alternating quantity. By designing the third electrode in the form of an external, external electrode, a particularly simple construction of the medical system can be achieved.

In a further embodiment of the invention, the coupling device is assigned an alternating current source and / or an alternating voltage source and / or a noise signal source and / or a multi-frequency signal source by means of which the electrical alternating quantity can be generated. The coupling device preferably has the corresponding source or sources.

In a further embodiment of the invention, the second electrode is arranged on a distal end section of the invasive component, the first electrode being arranged at a distance from the second electrode in the proximal direction. The distal end section of the invasive component forms a foremost region of the invasive component in the distal direction. The distal end section is preferably designed in the form of a point which is provided for insertion and / or piercing into the body tissue. By arranging the second electrode on the distal end section, the determination of the local tissue type is significantly influenced by the tissue section arranged in the area of the distal end section during operation of the medical system.

In a further embodiment of the invention, the second electrode has small dimensions compared to the first electrode. A particularly strongly localized determination of the tissue type can be achieved in this way.

In a further embodiment of the invention, the dimensions of the second electrode are by a factor of 2 to 5, preferably by a factor of 5 to 10, and particularly preferably by a factor of 10 to 50, smaller than the dimensions of the first electrode. Such a size configuration of the second electrode in relation to the first electrode has proven to be particularly advantageous.

In a further embodiment of the invention, the medical invasive component is designed as a catheter or cannula.

• 1 zeigt in stark vereinfachter schematischer Darstellung eine Ausführungsform eines erfindungsgemäßen medizinischen Systems, das zur Ausführung einer Ausführungsform des erfindungsgemäßen Verfahrens zur Ermittlung eines lokalen Gewebetyps eines Körpergewebes eingerichtet ist, und
• 2 in schematischer Flussdiagramm-Darstellung eine Ausführungsform des erfindungsgemäßen Verfahrens.

Further advantages and features of the invention emerge from the claims and from the following description of a preferred exemplary embodiment of the invention, which is illustrated with reference to the drawings.

• 1 shows in a greatly simplified schematic representation an embodiment of a medical system according to the invention, which is set up to carry out an embodiment of the method according to the invention for determining a local tissue type of a body tissue,
• 2 in a schematic flow diagram representation, an embodiment of the method according to the invention.

According to 1 is a medical system 1 to determine a local tissue type T of a body tissue K intended.

The medical system 1 has a coupling device 2 , 3 , a medical invasive component 4th with a first electrode 5 and a second electrode 6th , a detection device 7th and a determination device 8th on.

In the embodiment shown, the medical invasive component is a cannula 4th designed, but this is not mandatory. In an embodiment not shown, the medical component is invasive 4th for example designed as a catheter.

The cannula 4th has a distal end portion 9 on, which forms a cannula tip. Here is the second electrode 6th present in the area of the cannula tip 9 arranged and along a longitudinal axis L. by an unspecified distance from the first electrode 5 spaced. The first electrode 5 is offset to the rear in the proximal direction P relative to the second electrode and to that extent away from the cannula tip 9 arranged.

The cannula 4th is in the based 1 apparent configuration at least in sections, namely in the area of the first electrode 5 and the second electrode 6th , within the body tissue K arranged. The cannula 4th into the body tissue in a basically known way K be inserted or plugged in. In the based 1 apparent configuration is the cannula tip 9 with the second electrode arranged thereon 6th in the area of a local tissue section A. of the body tissue K arranged.

The body tissue K can in particular be human or animal tissue, which can be either living or dead body tissue.

The first electrode 5 and the second electrode 6th are each based on 1 dashed and unspecified signal lines with the detection device 7th connected, the further structure and function of the detection device 7th will be described in more detail.

The coupling device 2 , 3 is for coupling an electrical alternating quantity into the body tissue K intended. In the embodiment shown, the coupling device is 2 , 3 set up for coupling in the alternating quantity in the form of an electrical alternating voltage. For this purpose, the coupling device 2 , 3 an alternating voltage source 3 which is set up to generate the alternating voltage. The AC voltage source 3 is set up to generate the alternating voltage with a frequency that changes over time. In an embodiment not shown, the coupling device can have an alternating current source, a noise signal source and / or a multi-frequency signal source for generating a corresponding alternating quantity instead of the alternating voltage source. The coupling device 2 , 3 also has a third electrode 2 in the embodiment shown as an external electrode for application to the body tissue K is designed. The third electrode 2 is an external electrode, which is based on the 1 The configuration shown is electrically conductive in a fundamentally known manner to an external and unspecified surface of the body tissue K is upset. The third electrode 2 is electrically conductive to the AC voltage source by means of a signal line, which is not specified 3 connected.

To determine the tissue type T is by means of the coupling device 2 , 3 the electrical alternating quantity in the form of said and by means of the alternating voltage source 3 generated alternating voltage in the body tissue K coupled. The actual coupling takes place here by means of the third electrode 2 . As a result of the coupled alternating voltage, an electric field is created within the body tissue. The voltage potential between the first electrode that results within this electric field 5 and the second electrode 6th is by means of the detection device 7th measured. In the embodiment shown, this measurement takes place for different frequencies of the coupled-in AC voltage, so that a resulting voltage spectrum is recorded. In addition, the coupled alternating quantity can be recorded.

The voltage spectrum recorded is largely determined by the electrical properties of the tissue section A. in the area of the cannula tip 9 influenced. The one in the proximal direction P behind the first electrode 5 located, unspecified area of the body tissue K is comparatively less relevant, so that a type of directional characteristic oriented in the distal direction D is used when determining the tissue type T results. This is based on the in 1 Dotted oval area A. clarified.

Based on the in this way by means of the detection device 7th detected voltage spectrum is the local tissue type T in the area of the tissue section A. by means of the determination device 8th determined. The determination can also take place on the basis of the coupled alternating variables. In the embodiment shown, the determining device 8th a memory unit for this purpose 10 and a processor unit 11 on. The local tissue type is determined T in particular by means of a comparison of the recorded voltage spectrum with different reference spectra that are determined for different tissue types and based on data in the storage unit 10 are deposited. The comparison takes place data-based and / or computer-aided by means of the processor unit 11 .

The investigative facility 8th is in the embodiment shown by means of unspecified signal lines both with the coupling device 2 , 3 as well as with the detection device 7th connected. In this respect, an - at least indirect - signal connection between the detection device can also be used 7th and the coupling device 2 , 3 be trained.

How further based on 1 can be seen, has the second electrode 6th small in size compared to the first electrode. In the embodiment shown, the second electrode is smaller than the first electrode by a significant factor 5 . Such a sizing of the first electrode 5 and the second electrode 6th has been found to be beneficial because of the tissue type T as a result, in particularly localized areas and on the cannula tip 9 can be determined in a focused manner. Here the second electrode is by a factor 5 smaller, which is to be understood as purely exemplary.

Based 2 is that in terms of the medical system 1 Method V already described for determining the local tissue type T again illustrated schematically. In a first step a) the electrical alternating quantity is present in the form of an alternating voltage in the body tissue K coupled in, the AC voltage being coupled in at a frequency that changes over time. In the present case, a range between 1 kHz and 1 MHz is selected as the frequency range, which, however, is to be understood as purely exemplary. Alternatively or additionally, an alternating current, a band-limited noise signal and / or a multi-frequency signal can be coupled in. In a further step b), the voltage spectrum of the electrical voltage between the first electrode that results as a function of the coupled-in alternating quantity is used 5 and the second electrode 6th detected. The voltage spectrum is recorded on the basis of the 1 described manner and based on the specific arrangement and wiring of the first electrode 5 and the second electrode 6th . In a further step c) the local tissue type T in the area of the tissue section A. determined as a function of the recorded voltage spectrum. In addition, the determination can be made on the basis of the coupled alternating variable. The alternating variable is preferably regulated, so that there is no need to record it. In the present case, this takes place by means of the determination device already described 8th with recourse to the reference spectra stored in the memory unit C and using the processor unit 11 .

Claims (12)

Method (V) for determining a local tissue type (T) of a body tissue (K), comprising the steps: a) coupling an electrical alternating quantity into the body tissue (K); b) Acquisition of a signal of an electrical voltage resulting as a function of the coupled-in alternating quantity, the electrical voltage being measured between a first electrode (5) and a second electrode (6), the first electrode (5) and the second electrode (6 ) are arranged on a medical invasive component (4) and are spaced apart from one another by a distance along a longitudinal axis (L) of the invasive component (4), and wherein the medical invasive component (4) is arranged in the body tissue (K) and the longitudinal axis (L) extends in the region of a local tissue section (A) of the body tissue (K); c) Determining the local tissue type (T) in the region of the tissue section (A) as a function of the detected signal. Procedure (V) according to Claim 1 , characterized in that the changing size in the form of a AC voltage and / or an AC current and / or a band-limited noise signal and / or a multi-frequency signal is coupled. Procedure (V) according to Claim 1 or 2 , characterized in that the alternating variable is coupled in with a frequency that changes over time. Medical system (1) for determining a local tissue type (T) of a body tissue (K), having - a coupling device (2, 3) which is set up to couple an electrical alternating variable into the body tissue, - A medical invasive component (4) provided for introduction into the body tissue (K) and having a first electrode (5) and a second electrode (6), the first electrode (5) and the second electrode (6) along a longitudinal axis (L ) the invasive component (4) are arranged at a distance from one another, - A detection device (7), which is connected to the first electrode (5) and the second electrode (6) and for detecting a signal resulting from the coupled alternating quantity between the first electrode (5) and the second electrode (6) measured electrical voltage is set up, and a determination device (8) which is set up to determine the local tissue type (T) as a function of the detected signal. Medical system (1) according to Claim 4 , characterized in that the coupling device (2, 3) is set up to couple the alternating quantity in the form of an alternating voltage and / or an alternating current and / or a band-limited noise signal and / or a multi-frequency signal. Medical system (1) according to Claim 4 or 5 , characterized in that the coupling device (2, 3) is set up for coupling in the alternating variable with a frequency that changes over time. Medical system (1) according to one of the Claims 4 to 6th , characterized in that the coupling device (2, 3) has a third electrode (2) which is provided for external application to the body tissue (K). Medical system (1) according to one of the Claims 4 to 7th , characterized in that the coupling device (2, 3) is assigned an alternating current source and / or an alternating voltage source (3) and / or a noise signal source and / or a multi-frequency signal source by means of which the electrical alternating variable can be generated. Medical system (1) according to one of the Claims 4 to 8th , characterized in that the second electrode (6) is arranged on a distal end section (9) of the invasive component (4), the first electrode (5) being arranged at a distance from the second electrode (6) in the proximal direction (P). Medical system according to one of the Claims 4 to 9 , characterized in that the second electrode (6) has small dimensions compared to the first electrode (5). Medical system (1) according to Claim 10 , characterized in that the dimensions of the second electrode (6) are smaller by a factor of 2 to 5, preferably by a factor of 5 to 10, and particularly preferably by a factor of 10 to 50, than the dimensions of the first electrode 5. Medical system (1) according to one of the Claims 4 to 11 , characterized in that the medical invasive component is designed as a catheter or cannula (4).

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