Integrated differential voltage measurement system

Abstract

The invention relates to an integrated differential voltage measuring system (1) for measuring a bioelectric signal (S(k)) of a patient (P), the differential voltage measuring system (1) having at least two signal measuring circuits (30), which each comprise a sensor electrode (3, 4), a reference measuring circuit, which comprises a reference electrode (5), and a common conductive electrode cover (3a), wherein the conductive electrode cover covers at least one area formed by the bottom surfaces of the sensor electrodes and the reference electrode.

Description

Technical Field

[0001] The present invention relates to an integrated differential voltage measurement system for measuring the bioelectrical signals of a patient, the integrated differential voltage measurement system including, in particular, conductive electrode covers. Background Technology

[0002] Voltage measurement systems, especially differential voltage measurement systems, are used to measure bioelectrical signals, such as electrocardiograms (ECG), electroencephalograms (EEG), or electromyograms (EMG) in medicine.

[0003] Especially for cardiac imaging, it is necessary to use the aforementioned voltage measurement system to measure cardiac activity so that the imaging process matches the very distinct movement of the heart during a heartbeat. This requires the use of conventional sensors that must be securely fastened to the patient's body. A feasible method for heartbeat measurement is capacitive ECG, where the ECG signal is captured purely capacitively, without direct contact between the patient and the sensor, especially without contact through the patient's clothing. To achieve good signal quality for the heartbeat signal, the measured signal amplitude must preferably be large. This can be achieved through a large capacitance between the patient and the sensor. The size of the coupling surface between the sensor and the patient affects the capacitance. The larger the coupling surface, the larger the capacitance achieved.

[0004] To suppress interference with measurement signals, it is known to implement protective measures, such as grounding or reference electrodes or neutral drive electrodes (NDEs) for voltage measurement systems. These protective measures are typically configured, at least partially, as sensor elements separate from the sensor electrodes that detect the measurement signals. This increases the preparation time for capacitive ECG measurements because different sensor elements must be positioned or held in the desired locations at the patient's site.

[0005] Furthermore, capacitive ECG devices are known to be layered and integrated into conductive textiles, where conductivity is achieved, for example, through a vapor deposition process utilizing conductive particles. In this case, the reference electrode is typically implemented as a separate sensor element. Moreover, using textiles in the sensor element makes the cleaning process difficult. Additionally, textiles are not X-ray transparent and are therefore unsuitable for triggering arbitrary medical image data detection. Summary of the Invention

[0006] In contrast, the object of the present invention is to provide a mechanism that provides reliable interference suppression with simple operation and meets the hygiene requirements of clinical environments in terms of watertightness and cleanability.

[0007] The objective is achieved by the differential voltage measurement system according to the invention. Further particularly advantageous designs and improvements of the invention will be derived from the following description, wherein features of different embodiments or variations can also be combined to form new embodiments or variations.

[0008] This invention relates to an integrated differential voltage measurement system for measuring bioelectrical signals in patients. The differential voltage measurement system according to the invention detects bioelectrical signals, such as those of human or animal patients. For this purpose, the integrated differential voltage measurement system has multiple measurement lines or effective signal paths. These measurement lines or effective signal paths, for example as a single cable, connect electrodes mounted at the patient to detect signals to other components of the voltage measurement system, i.e., particularly electronic devices, for evaluating or displaying the detected bioelectrical signals, particularly heartbeat signals.

[0009] Differential voltage measurement systems can be configured as electrocardiogram (ECG), electroencephalogram (EEG), or electromyogram (EMG).

[0010] A differential voltage measurement system has at least two signal measurement circuits, each corresponding to an effective signal path and each including a sensor electrode. The voltage measurement system may include exactly two, but more than two, signal measurement circuits.

[0011] In addition to the sensor electrodes, the signal measurement circuit also includes a measurement amplifier circuit and a sensor line between the measurement amplifier circuit and the sensor electrodes. In an embodiment of the invention, the sensor line is used to transmit the bioelectrical measurement signal detected by means of the sensor electrodes to the corresponding measurement amplifier circuit. The measurement amplifier circuit preferably includes an operational amplifier, which can be configured as a so-called follower. That is, the negative input terminal, also known as the inverting input terminal, of the operational amplifier is coupled to the output terminal of the operational amplifier, thereby generating a high virtual input impedance at the positive input terminal.

[0012] The voltage measurement system also includes a reference measurement circuit, which includes a reference electrode. The reference electrode and the associated reference measurement circuit are used to achieve potential balance between the patient and the ECG measurement device. In embodiments of the invention, the reference measurement circuit also includes signal lines and operational amplifiers.

[0013] The sensor electrode and reference electrode are each configured as surface electrodes and have a film-like structure. In other words, the dimensions of the sensor electrode and reference electrode in one spatial dimension are significantly smaller than their dimensions in the other two spatial dimensions. The electrodes can be arbitrarily shaped. The sensor electrode can, in particular, have a circular, quadrilateral, or, for example, elliptical base surface. The sensor electrode and reference electrode can be constructed from or include at least one of the following materials: metal plates or metal films, vapor-deposited or otherwise conductive textiles, or other conductive materials such as carbon or materials containing carbon mixtures.

[0014] The sensor electrodes and reference electrodes are particularly layered. Both electrode types have at least one conductive layer. The conductive layers preferably have a sheet resistance of up to 100 kOhm. The conductive layers are oriented toward the electrode cover or the patient.

[0015] Furthermore, in the implementation, each sensor electrode in the sensor electrodes includes an additional layer, for example, for passive shielding against strong electromagnetic interference radiation or for active shielding to provide high input impedance. The reference electrode may also include an additional shielding layer. All additional layers are disposed on the side of the conductive layer facing away from the patient.

[0016] According to the present invention, the sensor electrode and the reference electrode are disposed adjacent to each other or disposed in each other in a planar manner in a coplanar manner. The sensor electrode and the reference electrode have a defined distance relative to each other. The reference electrode is configured such that it at least partially surrounds the sensor electrode.

[0017] The sensor electrodes have the following diameter or side length: in circular or square embodiments, the diameter or side length is in the range of 3 cm to 6 cm, preferably 4 cm to 5 cm. In a preferred embodiment of the invention, the sensor electrodes have the same basic shape, but may also have different shapes.

[0018] The reference electrode has a diameter or maximum side length in the range of 15 cm to 30 cm, preferably in the range of 18 cm to 25 cm.

[0019] The sensor circuitry of the signal measurement circuit transmits the measurement signal detected by means of sensor electrodes to the measurement amplifier circuit. The measurement amplifier circuit preferably includes an operational amplifier, which can be configured as a so-called follower. That is, the negative input terminal, also known as the inverting input terminal, of the operational amplifier is coupled to the output terminal of the operational amplifier, thereby generating a high virtual input impedance at the positive input terminal.

[0020] According to the present invention, the sensor lines and signal lines, as well as the signal measurement circuit and other components of the reference measurement circuit are disposed outside the electrode plane, preferably on the side of the electrode plane facing away from the patient.

[0021] The voltage measurement system according to the invention is further characterized by a common conductive electrode cover, which covers at least one area formed by the bottom surfaces of the sensor electrode and the reference electrode. The conductive electrode cover is a single piece.

[0022] In other words, the common electrode cover covers not only the two sensor electrodes but also the reference electrode. In an embodiment, the electrode cover extends beyond the surface formed by the bottom surfaces of the sensor and reference electrodes, i.e., it is larger in itself. In a preferred embodiment of the invention, the electrode cover has a diameter or maximum side length in the range of 15 cm to 30 cm, preferably between 20 cm and 35 cm.

[0023] According to the present invention, a sensor element is integrally formed by a sensor electrode, a reference electrode, and a conductive electrode cover or a voltage measurement system according to the present invention, the sensor element being positioned at or on a patient for ECG measurement and for not only ECG signal detection but also for potential balancing.

[0024] The preparation costs for ECG measurements can be reduced in this manner, as only one or a small number of sensor elements need to be positioned on the patient.

[0025] This invention is based on the understanding that textiles, especially those containing cotton, have a volume resistivity between 100 MOhm and 1000 MOhm when dry. Practice has shown that, by means of spraying or wetting with the patient's sweat, the volume resistivity of cotton and many other textiles typically decreases to below 10 MOhm, and in some cases even to below 1 MOhm, during ECG measurements.

[0026] Therefore, constructing a purely capacitive ECG by embedding electrodes into the textile layer is not considered meaningful, because the ohmic connection would be suppressed in this case.

[0027] According to the present invention, the differential voltage measurement system now operates not only using an ohmic insulating layer but also simultaneously utilizing an ohmic conductive layer to fully leverage the advantages of said conductivity. Therefore, the differential voltage measurement system according to the present invention is configured to also establish an ohmic conductive connection. The differential voltage measurement system is particularly advantageously configured to have a maximum volume resistivity of 10 MOhm in a dry state and a maximum volume resistivity of 1 MOhm when moisture is added.

[0028] The following resistance specifications correspond in this document to the requirements of DIN EN 61340-2-3 (VDE0300-2-3), Electrostatics – Part 2-3: Methods for determining the resistance and resistivity of solid materials for the purpose of avoiding the accumulation of electrostatic charge (IEC 61340-2-3:2016).

[0029] The present invention is particularly advantageous in applying conductivity not only to the sensor electrodes, but also to interference suppression by means of the reference electrode.

[0030] The conductive configuration of the electrode cover, sensor electrodes, and other electrodes allows for an ohmic connection between the patient and the electrodes under suitable environmental conditions, in addition to capacitive coupling for capacitive ECG signal measurements. In this case, the capacitive reactance and ohmic resistance are connected in parallel.

[0031] In implementations of the differential voltage measurement system, the conductive electrode cover has a layer thickness of less than 100 μm, preferably 50 μm. The thinner the electrode cover, the better it can be deformed, and the more it contributes to a particularly low profile of the sensor element. However, thicker design variations are also feasible, for example, in the range of a few millimeters.

[0032] In implementations of the differential voltage measurement system, the conductive electrode cover is formed of plastic, such as polyamide (PA), polyethylene (PE), polypropylene (PP), polyurethane (PU), polyolefin, or polyvinyl chloride (PVC), from which the aforementioned thin layers / films can be manufactured and further processed particularly easily. Furthermore, plastics offer particularly good cleaning properties compared to textiles due to their smooth, washable, and disinfectable surfaces.

[0033] To achieve the desired conductivity of the electrode cover, in embodiments of the differential voltage measurement system, the electrode cover, or the material forming the electrode cover, is enriched with carbon particles. The particles are preferably nanoparticles. The degree of carbon dopant filling is related to the desired conductivity and the type of carbon particles. In selecting carbon particles, the increasing effect on mechanical properties with higher filling degrees should be considered. Sufficient conductivity has already been achieved with very low filling degrees of only a few volume percentages using carbon nanotubes (CNTs).

[0034] In another embodiment of the differential voltage measurement system, the conductive electrode cover is made of a hygroscopic material. Textiles, such as cotton, in addition to some plastics, also possess this property. Hygroscopic materials are characterized by their ability to absorb and retain water. The hygroscopic material can bind moisture, and this allows for a moisture-related adaptation of conductivity, or particularly volume resistivity. The electrode cover is preferably configured to reduce the volume resistivity to below 1 MOhm by introducing liquids, such as sweat or water. This value corresponds to the conductivity achieved by the ECG device when using a textile comprising cotton or a low-conductivity base material with conductive additives for ohmic connection. In this manner, a high-quality ECG signal can be derived by means of an ohmic connection using the differential voltage measurement system.

[0035] In a particularly preferred embodiment, the conductive electrode cover is made of hygroscopic plastic, which combines the adaptability of conductivity with the robustness and good handling properties of plastic.

[0036] In embodiments of the invention, the conductive electrode cover is configured such that it has a sheet resistance greater than 500 MOhm or a volume resistivity less than 100 MOhm. The values ​​used for sheet resistance and volume resistivity are advantageous limiting values ​​to achieve the advantages of the ohmic connection with low volume resistivity, and to avoid undesirably increasing the sensor surface area and establishing contact with other components with high sheet resistance. The resistance specification relates to dry environmental conditions where no moisture is introduced into the material of the electrode cover.

[0037] In embodiments of the invention, the bottom surface of the reference electrode is several times larger than the bottom surface of the sensor electrode. Therefore, the bottom surface of the reference electrode can be twice or several times larger than the bottom surface of the sensor electrode. The bottom surface of the reference electrode preferably completely or substantially completely / largely covers the area between the sensor electrodes so that when the sensor element formed by the differential voltage measurement system is positioned at the patient and the patient largely covers the different electrodes, a large capacitance is generated on the one hand, and a low ohmic resistance is generated on the other.

[0038] To keep the overall size of the differential voltage measurement system according to the invention within acceptable limits, in embodiments of the invention, reference electrodes are formed such that they each surround the sensor electrodes over an angular range of at least 180°. In a quadrilateral configuration of the sensor electrodes, this means that the reference electrodes surround the sensor electrodes at least on their adjacent sides. Therefore, the reference electrodes can extend at least partially between, beside, or externally to the sensor electrodes. This advantageously utilizes the area between the sensor electrodes for potential balance achieved using the reference electrodes.

[0039] In one embodiment, the reference electrode further has a spacing from each of the sensor electrodes, such that the impedance between the reference electrode and each sensor electrode is greater than 100 MOhm. This impedance value is achieved when the spacing is between 0.5 cm and 1.5 cm, particularly 1 cm.

[0040] In a particularly advantageous embodiment of the invention, the differential voltage measurement system also includes a grounding circuit comprising a grounding electrode, the bottom surface of which is covered by a conductive electrode cover. This arrangement corresponds to an additional integration stage for the differential voltage measurement system, in which the grounding circuit is now also integrated into the differential voltage measurement system, where the conductive electrode cover is also utilized for this purpose.

[0041] The grounding electrode is also configured as a surface electrode with a layered or thin-film structure, and is similarly disposed on the same plane as the sensor electrode and the reference electrode. The grounding electrode is also advantageously configured in a large manner and is disposed in a space-saving manner between, beside, or outside, or at least partially surrounding, the sensor electrode and / or the reference electrode. The grounding electrode also has a conductive layer oriented towards the patient and having a sheet resistance of no more than 100 kOhm. An additional shielding layer may be provided on the side facing away from the patient.

[0042] The differential voltage measurement system should be configured such that the impedance between the ground electrode and each of the sensor electrodes reaches at least 1 GOhm, preferably at least 10 GOhm. This impedance value is achieved by selecting a spacing between the ground electrode and each sensor electrode between 1.5 cm and 2.5 cm, preferably 2 cm.

[0043] In principle, the stricter requirements apply to the spacing between the ground electrode and the sensor electrode, rather than the spacing between the reference electrode and the sensor electrode. With smaller impedance values, there is a risk that electrical interference to the measured ECG signal may be amplified through the ground electrode. If the expected electrical interference is minimal and permitted by specifications, impedance can also be reduced by decreasing the spacing.

[0044] The differential voltage measurement system should also be configured to achieve an impedance value of at least 200 MOhm, preferably at least 200 MOhm, between the ground electrode and the reference electrode. This impedance value is achieved by selecting a spacing between the ground electrode and the reference electrode that is between 0.5 cm and 2.5 cm, preferably 1 cm. Attached Figure Description

[0045] The invention will be described in detail again below with reference to the accompanying drawings and embodiments. Here, the same parts are given the same reference numerals in different drawings. The drawings are generally not to scale. The drawings show:

[0046] Figure 1 A view of a differential voltage measurement system disposed at a patient location in one embodiment is shown.

[0047] Figure 2 A view of a differential voltage measurement system in another embodiment is shown.

[0048] Figure 3 A detailed view of a differential voltage measurement system in another embodiment is shown, and

[0049] Figure 4 Another detailed view of a differential voltage measurement system in one embodiment is shown. Detailed Implementation

[0050] In the accompanying drawings, the ECG measurement system 1, which is exemplarily a differential voltage measurement system 1, is used to measure the bioelectrical signal S(k), and here the ECG signal S(k). However, the invention is not limited thereto.

[0051] Figure 1 A view is shown of a differential voltage measurement system 1 in the form of an ECG measurement system 1 disposed at a patient P in one embodiment. The voltage measurement system 1 includes an ECG device 17 with its electrical terminals and electrodes 3, 4, 5 connected thereto via cables K to measure the ECG signal S(k) at the patient P.

[0052] To measure the ECG signal S(k), at least one first sensor electrode 3 and a second sensor electrode 4 are required, positioned at, on, or below the patient P. Electrodes 3 and 4 are connected to the ECG device 17 via a signal measurement cable K, through terminals 25a and 25b, which are typically plug-in connectors. Here, the first electrode 3 and the second electrode 4, together with the signal measurement cable K, form part of a signal detection unit, which is used to detect the ECG signal S(k).

[0053] The third electrode 5 serves as a reference electrode to achieve potential balance between the patient P and the ECG device 17. Typically, the third electrode 5 is positioned on the patient P's right leg ("Right Leg Drive" or "RLD") via a separate sensor element. However, here, the third electrode 5 is an integral part of the sensor element 1a, forming together with sensor electrodes 3 and 4, as further detailed with reference to other figures. Furthermore, multiple additional contacts for other leads (potential measurement units) can be positioned at the patient P via additional terminals (not shown) at the ECG device 17 to generate suitable signals. Additionally, the sensor element 1a may have additional sensor electrodes (not shown here).

[0054] A voltage potential UEKG is formed between electrodes 3, 4, and 5 for measuring the ECG signal S(k). 34 UEKG 45 and UEKG 35 .

[0055] The directly measured ECG signal S(k) is displayed on the user interface 14 of the ECG device 27.

[0056] In ECG measurements, patient P is at least capacitively coupled to ground potential E via a grounding circuit (shown via coupling at the right leg), which is also configured as a separate sensor element. This grounding circuit includes a grounding electrode 6. Alternatively or in parallel with this, the coupling in the separate sensor element can also be ohmic in a corresponding design.

[0057] In an alternative embodiment, as shown in another figure, the ground electrode may also be an integral part of the sensor element 1a.

[0058] The signal measurement cable K, which leads from the first sensor electrode 3 and the second sensor electrode 4 to the ECG device 17, is part of the effective signal paths 6a and 6b. The signal measurement cable K, which leads from the reference electrode 5 to the ECG device 17, here corresponds to a part of the third effective signal path 7N. The third effective signal path 7N transmits interference signals coupled to the patient P and the electrodes.

[0059] Cable K has a shield S, which is schematically shown here as a dashed column surrounding all valid signal paths 6a, 6b, 7N. However, the shield does not necessarily surround all cables K; cables K can also be shielded individually. Terminals 25a, 25b, 25c preferably have poles integrated for the shield S. These poles are then guided together to a common shield terminal 25d. The shield S is configured here, for example, as a thin metal film surrounding the conductor of the respective cable K, the metal film being insulated from the conductor.

[0060] In addition, such as in Figure 1 As shown, the ECG device 17 may have an external interface 15 to provide terminals for, for example, printers, storage devices, and / or even networks. According to an embodiment of the invention, the ECG device 17 also has signal measurement circuitry 30 associated with the corresponding terminals 25a, 25b (see, for example, [link to relevant documentation]). Figure 3 ).

[0061] Figure 2 A view of a differential voltage measurement system 1 according to another embodiment of the present invention is shown. In one embodiment, the differential voltage measurement system 1 includes four signal measurement circuits 30. The four signal measurement circuits 30 have the same construction, so corresponding components of the signal measurement circuits 30 are actually referred to only once for overview purposes.

[0062] The arrangement of individual sensor electrodes 3 and 4 is illustrated here in the form of a substantially capacitive ECG measurement circuit. The patient P and sensor electrodes 3 are spatially close to each other. More precisely, the sensor element 1a, including sensor electrodes 3 and 4, is placed flat or attached to the patient P.

[0063] In this embodiment, sensor element 1a has a slightly trapezoidal basic shape with rounded corners. The entire bottom surface of sensor element 1a, measuring 36cm x 24cm, is covered by electrode cover 3a. Sensor electrodes 3 and 4 currently have a square basic shape with a side length of 5cm. Sensor electrodes 3 and 4 are positioned at intervals of 4cm to 5cm from the edge, moving towards the corners of sensor element 1a.

[0064] The construction of the signal measurement circuit 30 is described in detail below. The patient P may, for example, be provided with clothing made of material C. The sensor element 1a is mechanically stabilized by a support structure 22, for example, a plastic housing with a compressible, stable filling material, such as PU foam. Sensor electrodes 3 and 4, as well as the other two sensor electrodes, are covered by a common electrode cover 3a. The electrode cover 3a is configured as a conductive cover layer. Sensor electrodes 3 and 4 also include conductive layers. The electrode cover 3a does not cause complete ohmic insulation between the sensor electrodes 3 and 4 and the patient P. In this respect, the sensor electrodes 3 and 4 serve as ohmic resistors connected in parallel with the capacitive reactance between the patient P and the sensor electrodes 3 and 4. In any case, the sensor electrodes 3 and 4 can be capacitively coupled to the patient P. Furthermore, under suitable patient clothing and / or corresponding ambient temperature or ambient (air) humidity conditions, the conductive layers of the electrode cover 3a and the sensor electrodes 3 and 4 allow ohmic connection between the patient P and the sensor electrodes 3 and 4. The capacitive coupling input of the ECG signal to sensor electrodes 3 and 4 is not obstructed by the sensor cover 3a.

[0065] The setup offers the following advantages:

[0066] By connecting the capacitive reactance and ohmic resistance in parallel using the conductive electrode cover 3a, a significantly smaller impedance is formed compared to pure capacitive coupling. This results in improved ECG signal quality, similar to that of conventional ohmically coupled ECG devices with adhesive electrodes or wrist clips.

[0067] This allows for the formation of the full characteristics of a classic ECG signal shape with all its individual segments, where low-frequency components, such as the T-wave (T-Welle), are not suppressed.

[0068] Because the electrode cover 3a extends over the largest possible surface of the sensor element 1a, electrostatic discharge (ESD) is possible across the entire surface, resulting in less signal interference.

[0069] The common, fully enclosed electrode cover 3a can be easily manufactured, and the corresponding sensor element 1a is also simple to construct. The electrode cover 3a, especially if it is made of a plastic film, can achieve a smooth, hygienic surface with good cleaning properties.

[0070] If the patient is wearing textile clothing with a volume resistivity of less than 10 GOhm, such as cotton or any other woven material that is minimally vaporized or sweat-soaked, electrostatic charge accumulation occurs in the patient P via the electrode cover 3a, which causes faster signal initialization.

[0071] The sensor electrode 3, the sensor line 6a extending from the sensor electrode 3 to the operational amplifier 27, and the measurement circuit 30 including the operational amplifier 27 are surrounded by a so-called active protection barrier 25 and preferably a shield S. The operational amplifier 27 is configured as a so-called follower. That is, the negative input terminal 27a of the operational amplifier 27 is coupled to the output terminal 28 of the operational amplifier 27. In this way, a high virtual input impedance is achieved for the operational amplifier 27 at the positive input terminal 27b. That is to say, due to the voltage matching between the output terminal 28 and the positive input terminal 27b, almost no current flows between the sensor 3 and the active protection barrier 25. Furthermore, the positive input terminal 27b of the operational amplifier 27 is held at a bias voltage by means of a resistor 26 connected to the measurement equipment ground (also called "measuring ground"). Hereby, the positive input terminal can be placed at the desired measurement potential. In this way, DC components can be suppressed, especially during periods of primarily capacitive coupling.

[0072] The signal measurement circuit 30 is also connected to ground E via another ground plane ES.

[0073] The shield S is also connected to the device ground via terminal 31.

[0074] An active guard 25, a shield S, and a ground layer ES surround the sensor electrodes 3 and 4 respectively to effectively shield them. The active guard 25, shield S, and ground layer ES also surround the sensor line 6a and, together with it, reach the operational amplifier 27 via the carrier structure 22 in a suitable manner. The active guard 25, shield S, ground layer ES, sensor line 6a, and operational amplifier 27 are particularly positioned on the side of the sensor electrodes 3 and 4 facing away from the patient P.

[0075] The other electrode, which forms the ground electrode 6, is also disposed in the sensor element 1a shown here, for capacitively, but also ohmically, coupling the patient P to the ground potential E, and can be said to be integrated into the sensor element 1a. The ground electrode 6 here has a basic square shape and also has a side length of 5 cm. The distance from the sensor electrode here is 4 cm. With this distance, an impedance value much higher than 200 MOhm can be achieved.

[0076] The other electrode of the reference electrode 5, or the associated measurement circuit 36, is used in the sensor element 1a for potential derivation, for example, as a so-called driven neutral electrode (DNE). The reference electrode 5 has a basic shape that matches the arrangement and shape of the other electrodes, and substantially completely fills the area between the other electrodes, with a spacing of at least 1 mm from the other electrodes. This spacing allows for an impedance value much higher than 1 GOhm.

[0077] The reference electrode 5 and the ground electrode 6 are also spanned by the electrode cover 3a and have a conductive layer. By coupling the reference electrode 5 and the ground electrode 6 with low impedance, the increase in interference electric field is suppressed by up to 20 dB.

[0078] The differential voltage measurement system 1 may optionally include switching devices in the form of a switch matrix 33. In the case of multiple sensor electrodes, the switching devices are used, for example, to select which of the sensor electrodes are used for additional signal processing based on the patient's anatomy.

[0079] The differential voltage measurement system 1 may also include a signal processing device in the form of a signal processing box 34. This signal processing device is configured to perform preprocessing on the detected measurement signal to remove interference components. The signal processing device 34 can be configured to perform standard processing using frequency-based filters such as bandpass or bandstop filters, but also to perform extended interference suppression, for example, as described in German patent application DE 102019203627A.

[0080] Furthermore, the differential voltage measurement system 1 may also include a triggering device 35. The triggering device is configured to identify the patient P's heartbeat or rhythm and generate a control signal that includes trigger or start time information for the medical imaging device. Based on the control signal from the triggering device 35, the imaging device calculates the time for image data detection.

[0081] Figure 3 and Figure 4 Detailed views of the differential voltage measurement system 1 according to the invention in other embodiments are shown, with particular emphasis on the layered structure of the sensor element 1a according to the invention.

[0082] The integrated differential voltage measurement system 1 according to the present invention includes at least two sensor electrodes 3 and 4, which belong to the signal measurement circuit 30. The voltage measurement system here also includes two additional sensor electrodes, which may optionally be used to capture ECG signals.

[0083] Voltage measurement system 1 in Figure 3and Figure 4 This also includes the reference electrode 5, which belongs to the overall reference measurement circuit.

[0084] exist Figure 4 In the voltage measurement system 1, an integrated grounding electrode 6 belonging to the corresponding grounding circuit is also provided. Figure 3 In this system, the voltage measurement system includes a ground electrode located at another separate sensor element.

[0085] According to the present invention, not only sensor electrodes 3 and 4, but also reference electrode 5 and Figure 4 There is also a ground electrode 6, all covered by a common conductive electrode cover 3a, which spans at least one area formed by the bottom surfaces of the sensor electrode and the reference electrode. Currently, the electrode cover 3a is even larger and covers the surface formed by the bottom surface of the sensor element, and therefore still extends beyond the sensor electrode and the reference electrode.

[0086] The reference electrode 5, ground electrode 6, and sensor electrodes 3 and 4 (and other sensor electrodes) are configured as a flat, planar layer electrode, which is disposed on a plane of the sensor element 1a facing the patient P. The height of the different electrodes can be between 300 μm and 3 mm. Here, the electrode should have a thickness of 500 μm. The thinner the electrode, the thinner the corresponding sensor element. Furthermore, in the thinner electrode design, the plasticity of the electrode to the anatomical structure of the patient P can be optimized. The sensor electrode is configured as a square, and the reference electrode 5 or ground electrode 6 is disposed substantially between or partially adjacent to each other, and partially outside the plane extending through the sensor electrode. The reference electrode 5 is formed such that it surrounds the sensor electrode at least on both sides within an angular range of at least 180°, i.e., in the case of the base of the square. In an alternative embodiment, the reference electrode may also completely surround the sensor electrode.

[0087] The sensor electrode, reference electrode 5, and ground electrode 6 have a layered structure. Therefore, the sensor electrode, reference electrode 5, and ground electrode 6 consist of at least two layers. Each electrode includes at least one upper conductive layer, which can be configured in parallel with the patient P via a conductive electrode cover 3a and capacitive coupling, which, as described above, has a positive impact on ECG signal quality.

[0088] According to Figure 3 and Figure 4 In one embodiment, the conductive electrode cover 3a has a layer thickness of 80 μm to 90 μm, and is thus advantageously thin, which has a positive impact on the overall structural height of the sensor element 1a.

[0089] Currently, the electrode cover 3a is made of plastic, and carbon particles are embedded in the plastic to achieve the desired conductivity. Preferably, the filling degree is between 10 and 30% by volume.

[0090] According to the invention, the electrode cover 3a is designed such that it has a surface resistivity of at least 500 MOhm, preferably greater, and a volume resistivity of at most 100 MOhm, preferably less. The resistance specifications herein conform to DIN EN 61340-2-3 (VDE 0300-2-3) and Electrostatics – Part 2-3: Methods for determining the resistance and resistivity of solid materials for avoiding the accumulation of electrostatic charge (IEC 61340-2-3:2016).

[0091] exist Figure 3 and Figure 4 In this embodiment, the electrode cover is made of a hygroscopic material. This material binds water from the environment to its molecular structure, thereby potentially positively affecting the conductivity of the electrode cover 3a during signal detection.

[0092] Not only in Figure 3 Moreover Figure 4 In this context, the bottom surface of the reference electrode 5 has a size several times larger than the bottom surfaces of the sensor electrodes 3 and 4. The reference electrode also... Figure 4 The ground electrode 6 essentially fills the surface of sensor element 1a that extends through the sensor electrodes. In this manner, it is advantageous to achieve potential balance over a large area of ​​sensor element 1a, which results in high signal quality.

[0093] When different electrodes are arranged / distributed on the bottom surface of sensor element 1a, care should be taken to ensure that the interval between each electrode is large enough to achieve a sufficiently large impedance value.

[0094] Therefore, a spacing must be maintained between the reference electrode 5 and each sensor electrode in the sensor electrodes, which achieves an impedance of at least 100 MOhm between the reference electrode and the sensor electrode.

[0095] Reference Figure 4The following spacing shall be observed between the ground electrode 6 and each of the sensor electrodes, such that the impedance between the ground electrode 6 and the sensor electrode is at least 1 GΩ, and the following spacing shall be observed between the ground electrode 6 and the reference electrode 5, such that the impedance between the ground electrode 6 and the reference electrode 5 is at least 200 MOhm.

[0096] Finally, it should be reiterated that the devices described in detail above are merely embodiments, and these embodiments can be modified in different ways by those skilled in the art without departing from the scope of the invention. Therefore, the differential voltage measurement system can relate not only to ECG devices but also to other medical devices used to detect bioelectrical signals, such as EEG, EMG, etc. Furthermore, the use of the indefinite articles "a" or "an" does not preclude the related features from existing features from existing features.

[0097] If not explicitly stated, but meaningful and consistent with the invention, various embodiments, sub-aspects, or features of embodiments can be combined or interchanged with each other without departing from the scope of the invention. Unless explicitly stated otherwise, the advantages described in the reference embodiments of the invention also apply to other embodiments if applicable.

Claims

1. An integrated differential voltage measurement system (1) for measuring the bioelectrical signal (S(k)) of a patient (P), the differential voltage measurement system (1) having: - At least two signal measurement circuits (30), each of the signal measurement circuits (30) comprising: - Sensor electrodes (3, 4); - A reference measurement circuit, the reference measurement circuit including a reference electrode (5); as well as - A common conductive electrode cover (3a), wherein the conductive electrode cover covers at least one area formed by the bottom surfaces of the sensor electrode and the reference electrode. The conductive electrode cover is made of a hygroscopic material.

2. The differential voltage measurement system according to claim 1, wherein the sensor electrode and the reference electrode have a layered structure, and the layered structure respectively includes at least an upper conductive layer.

3. The differential voltage measurement system according to claim 1 or 2, wherein the conductive electrode cover has a layer thickness of less than 100 μm.

4. The differential voltage measurement system according to claim 1 or 2, wherein the conductive electrode cover is formed of plastic.

5. The differential voltage measurement system according to claim 4, wherein the conductive electrode cover is rich in carbon particles.

6. The differential voltage measurement system according to claim 1 or 2, wherein the conductive electrode cover has a surface resistance greater than 500 MOhm.

7. The differential voltage measurement system according to claim 1 or 2, wherein the conductive electrode cover has a volume resistivity of less than 100 MOhm.

8. The differential voltage measurement system according to claim 1 or 2, wherein the bottom surface of the reference electrode corresponds to several times the bottom surface of the sensor electrode.

9. The differential voltage measurement system according to claim 1 or 2, wherein the reference electrode is formed such that the reference electrode surrounds the sensor electrode in an angular range of at least 180°.

10. The differential voltage measurement system according to claim 1 or 2, wherein the reference electrode has a distance from the sensor electrode, and at this distance, the impedance between the reference electrode and the sensor electrode is greater than 100 MOhm.

11. The differential voltage measurement system according to claim 1 or 2, wherein the differential voltage measurement system further comprises: - A grounding circuit, the grounding circuit including a grounding electrode (6), the bottom surface of which is covered by the conductive electrode cover.

12. The differential voltage measurement system according to claim 11, wherein... - The grounding electrode is spaced from the sensor electrode such that the impedance between the grounding electrode and the sensor electrode is greater than 100Ω, and... - The ground electrode is spaced from the reference electrode such that the impedance between the ground electrode and the reference electrode is greater than 200 MOhm at that distance.

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