Lead set for biopotential recording system

Abstract

A leadset system is a system for delivering signals to a biopotential recording unit. The leadset has multiple leads, each defining an input channel to the biopotential recording unit. Correction information for the multiple leads is stored as part of the leadset system (i.e., independent of the biopotential recording unit) for use in interpreting the input channels, thereby improving channel symmetry.

Description

[Technical Field]

[0001] The present invention relates to a lead set for a biopotential recording system, and more particularly to reducing signal channel asymmetry in signals acquired by the lead set. [Background technology]

[0002] Biopotential measurements, such as electrocardiography (ECG / EKG) and electroencephalography (EEG), are an established part of clinical practice and are also used in other fields, such as research. Commercially available recording systems typically have a recording unit connected to an electrode lead set, which in turn is connected to electrodes (adhesives, needles, etc.) placed at defined locations on the patient's body.

[0003] The recording system measures small voltage differences between electrodes due to physiological electrical activity. Differential measurements are susceptible to interference from common-mode signals because common-mode to differential-mode conversion (CM2DM) occurs when the input channels do not behave identically before the differential operation. This difference in the behavior of the input channels is called channel asymmetry.

[0004] US 11 / 147517 discloses a method for reducing asymmetries in the electrical behavior of the input channels of a recording device, the aim of which is in particular to reduce asymmetries arising due to tolerances of electronic components in the recording unit.

[0005] However, channel asymmetry in biopotential recording systems is also caused by electrode lead sets. These lead sets are typically replaced more frequently than the recording device itself. These lead sets are considered supplies or accessories to the recording system. These lead sets may be single-use disposable accessories or may be reusable.

[0006] Electrode lead sets can be classified as "passive" or "active." Passive lead sets contain only electrical conductors and passive electronic components, such as resistors, capacitors, inductors, and diodes. Active lead sets also contain electronic components that amplify, buffer, or digitally sample the signal, such as an operational amplifier or an analog-to-digital converter (ADC). Active lead sets are used to achieve an improved signal-to-noise ratio compared to passive lead sets by locating the amplifier, buffer, or ADC as close to the patient as possible and limiting the length of the electrical connection traversed by the unbuffered signal.

[0007] The advantages of active lead sets are discussed, for example, in Dabbaghian A, Kassiri H, "An Active Electrode IC with Embedded Analog CMRR Enhancement for Interference- and Gain-Mismatch-Resilient EEG Recording." 2021 IEEE Biomedical Circuits and Systems Conference (BioCAS); DOI:10.1109 / BIOCAS49922.2021.9644952.

[0008] Whether the leadset is active or passive, if the leadset contains electronic components that are subject to tolerances, they will contribute to the asymmetry of the input channel. This will reduce the common-mode rejection ratio (CMRR) of the recording mechanism, making it more susceptible to noise and artifacts. Passive leadsets are usually, but not always, designed so that the contribution of noise and artifacts to the asymmetry of the input channel is negligible. On the other hand, active leadsets contain significant parts of the analog signal processing chain, and therefore have a significant impact on the asymmetry of the input channel. This is one reason that, in practice, limits the benefits and scope of application of active leadsets.

[0009] US2020 / 000411 and WO2022 / 073781 each disclose electrode lead sets in which test signals are applied to a physiological monitoring unit to allow filter coefficients to be calculated. Summary of the Invention [Problem to be solved by the invention]

[0010] Thus, the problem remains that electrode lead sets, particularly active electrode lead sets, contribute to asymmetry in the input channels of biopotential recording systems, which reduces signal quality and usefulness, and in the case of active electrode lead sets, also limits the benefit of locating the signal processing elements of the recording system closer to the patient. [Means for solving the problem]

[0011] The invention is defined by the independent claims, the dependent claims defining advantageous embodiments.

[0012] According to an example according to one aspect of the present invention, there is provided a leadset system for delivering signals to a biopotential recording unit, the leadset system comprising: a leadset having a plurality of leads, each lead defining an input channel to a biopotential recording unit; stored determined correction information for the plurality of leads for use in processing the input channels, whereby channel symmetry is improved; and The correction information is associated with a readset and is determined independently of the use or intended use of the readset.

[0013] Thus, the present invention provides an electrode lead set with associated stored calibration information. These combinations are referred to herein as a "lead set system." The calibration information can be accessed by a biopotential recording unit to which the lead set is connected. Access to the calibration information can use wired or wireless communication means.

[0014] The calibration information is independent of the biopotential recording unit in that it forms part of the lead set system for delivering signals to the biopotential recording unit, i.e., the calibration information is associated only with the lead set and can be used by different biopotential recording units.

[0015] The correction information is generated, for example, during leadset manufacture, by, for example, applying a calibration signal to the input of the leadset and recording the resulting signal at the output of the leadset. The correction information is "determined" in the sense that the information is associated with the physical leadset and is independent of the use or intended purpose of the leadset. Thus, the correction information is constant for each manufactured leadset.

[0016] By storing the correction information determined for a particular lead set, no separate calibration or testing process is required as part of lead set use. Instead, channel symmetry is improved during use based on already available correction information, which is provided with the lead set and is independent of the biopotential recording unit. No (further) performance measurements of the lead set by the biopotential recording unit are required. In fact, lead set performance measurements are not performed by the biopotential recording unit, since they are generated independently and prior to lead set use.

[0017] Lead sets are removable, and sometimes disposable, components, and the lead sets themselves may have different electrical characteristics due to either manufacturing or component tolerances, or even by design, and the electrical behavior of individual lead sets may differ significantly from any simulation used during calibration measurements of the recording device.

[0018] Therefore, the match / symmetry of the input channels is improved by performing calibration measurements on each manufactured leadset, and then the correction information is stored.

[0019] The output signals recorded during the calibration test can be processed into correction information in the form of a set of digital filter coefficients that the biopotential recording unit applies to the input channel signals. Thus, a set of equalizing digital filters is calculated and stored in the leadset system.

[0020] In conventional manner, each lead terminates in a contact electrode for placement on the skin, for example.

[0021] The correction information is used to specify or obtain filter coefficients that are used as part of the correction procedure, for example by applying a digital filter, such as filter coefficients for use after analog-to-digital conversion.

[0022] The correction information may be encrypted, which ensures that the correction information can only be used by authorized biopotential recording units. The biopotential recording unit includes a means for decrypting the correction information (e.g., a private decryption key or a means for authenticating the recording unit to the leadset).

[0023] In one example set, the stored correction information may be remote from the lead set, where the correction information is a separate entity from the lead set itself, but the correction information is still remote from the biopotential recording unit.

[0024] In another example set, the readset has a digital storage device that stores the correction information, where the correction information is stored on a device that is an integral part of the readset.

[0025] The digital storage device preferably comprises a non-volatile memory, and the correction information is therefore static compensation data associated with the readset.

[0026] The lead set system can have a connector for connecting the leads to the biopotential recording unit, where the connector has a digital storage device, such that the storage device is incorporated into the lead set connector.

[0027] The lead set system can further include a trunk cable for connecting to the biopotential recording unit, wherein the connector includes a trunk cable connector between the plurality of leads and the trunk cable, and in this configuration, the digital storage device is part of the trunk cable connector.

[0028] The lead set system is a lead set connector to which a plurality of leads are connected; a set of intermediate leads between the lead set connector and the trunk cable connector; wherein the lead set connector comprises a further digital storage device.

[0029] In this configuration, the digital storage device is part of both the leadset connector and the trunk cable connector, which means that different leadset segments each have their own correction information.

[0030] The present invention provides a leadset system as defined above; Biopotential recording unit and Also provided is a biopotential recording system having the same, wherein the biopotential recording unit is configured to read the stored correction information and improve the symmetry of the channel.

[0031] The correction information allows the signal processing chain to compensate for differences in transfer functions between multiple leads, thereby improving channel symmetry.

[0032] This defines the combination of a readset and a recording unit.

[0033] The biopotential recording unit may include, for example, a digital filter, where the biopotential recording unit is configured to use the correction information to set a digital filter for each lead of the lead set, for example, after digital sampling for analog-to-digital conversion.

[0034] The correction information may specify or be used to obtain filter coefficients that are used as part of the correction procedure.

[0035] The biopotential recording unit or lead set may, for example, include an analog-to-digital converter for each lead of the lead set, where the analog-to-digital converter is configured to sample the signal of each lead in a reference-referenced single-ended mode.

[0036] This allows a calibration to be applied to the signal of each input channel before calculating the difference between the individual input channels, which is obtained by analog circuitry after a digital sampling operation.

[0037] The biopotential recording unit may have a decryption system for decrypting the encrypted correction information.

[0038] The present invention also provides a method of processing a signal received from a leadset, the method comprising: receiving signals from leads of a leadset, each lead defining an input channel; accessing stored correction information for the leads of the readset, the correction information being associated with the readset and determined independent of the use or intended use of the readset; processing the input channel using the stored correction information, thereby improving the symmetry of the channel; and The processing of the input channels includes, for example, analog-to-digital conversion.

[0039] The invention also provides a computer program having computer program code adapted to perform the above method when the computer program is run on a computer.

[0040] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief explanation of the drawings]

[0041] For a better understanding of the present invention, and to show more clearly how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: [Figure 1] Figure 1 shows a system diagram of the biopotential recording system. [Figure 2] FIG. 2 shows an example of a lead set having multiple sections between the electrodes and the biopotential recording unit. [Figure 3] FIG. 3 shows a first example of a readset with locus storage of correction information. [Figure 4] FIG. 4 shows a second example of a readset with local storage of correction information. [Figure 5] FIG. 5 shows a third example of a readset with remote storage of correction information. [Figure 6]FIG. 6 illustrates a method for processing signals received from a leadset. DETAILED DESCRIPTION OF THE INVENTION

[0042] The present invention will be described with reference to the drawings. While the detailed description and specific examples set forth exemplary embodiments of the devices, systems, and methods, it should be understood that they are for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the devices, systems, and methods of the present invention will become better understood from the following description, the appended claims, and the accompanying drawings. It should be understood that the drawings are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the drawings to indicate the same or similar parts.

[0043] The present invention provides a leadset system for delivering signals to a biopotential recording unit. The leadset has multiple leads, each defining an input channel to the biopotential recording unit. Calibration information for the multiple leads is stored as part of the leadset system (i.e., independent of the biopotential recording unit) for use in interpreting the input channels, thereby improving channel symmetry.

[0044] "Channel symmetry" is improved when signals arriving at the biopotential recording unit from the patient electrodes experience similar signal transfer functions. In particular, the ability to extract signals of interest at the biopotential recording unit (after digital filtering) is improved when the combined signal transfer functions of the leads and associated digital filters are matched to different leads. In particular, common-mode interference is more reliably rejected, and therefore the common-mode rejection ratio is improved. Therefore, improving channel symmetry involves improving the matching of the signal transfer functions of the input channels, i.e., from the patient electrodes to the signal processing stages in the biopotential recording unit. The signal processing stages involve comparing signals received from different channels.

[0045] 1 shows a system diagram 100 of a biopotential recording unit in the form of an ECG device 108 that uses one or more filters 114 to improve signal quality when making electrophysiological measurements on a human 102. The filters 114 are specifically digital filters intended for channel equalization.

[0046] The biopotential recording unit 108 includes a lead set having electrodes 104 attached to the human 102 and leads 106 that provide a conductive path between the biopotential recording unit 108. The electrodes 104 can provide an electrical potential across the body of the human 102, which can be affected by changes in polarity of the heart 112. The placement of the electrodes 104 is selected to capture changes in polarity at different angles corresponding to the vector between the electrodes 104. As the electrical potential of the electrodes 104 changes due to changes in polarity of the heart 112, the biopotential recording unit 108 can process the change in potential and generate a resulting signal 110 that represents the electrical activity associated with the heart 112.

[0047] However, changes in the polarity of the heart 112 sometimes only slightly change the potential of the electrodes 104, making it difficult to distinguish the changes in potential from electrical interference. The electrical interference can be in the form of common-mode interference, which arises from external sources, such as interference in electrical lines, or from internal sources, such as capacitive coupling between parts of the biopotential recording unit 108.

[0048] Therefore, the accuracy of the measurement depends on the quality of the signals transmitted through the electrodes and their respective leads. In an ideal case, calculating the voltage difference means that any signal components that affect all electrodes equally will cancel out. Thus, common-mode interference is eliminated. However, if different leads have different transfer functions (and thus distort the signal reaching the biopotential recording unit differently), or if the amount of interference is too large compared to the signal, the overall pattern of electrical activity measured in the body will make the diagnosis inaccurate for medical diagnostic applications.

[0049] Common-mode interference affects many types of electrophysiological measurements. To reduce and / or eliminate such interference, channels of a measurement system can be calibrated to identify filter parameters to individually mitigate common-mode interference or voltage differences between electrodes. Filters can be applied to electrode signals before calculating voltage differences between electrodes.

[0050] To reduce and / or eliminate such interference, the biopotential recording unit 108 includes one or more hardware and / or software filters 114 for filtering the signals received at the electrodes 104. Each electrode 104 is assigned to a filter 114, and respective coefficients for each electrode 104 are provided to minimize time-domain differences and interferences in the signals from each electrode 104.

[0051] The system of FIG. 1 is known from US 11 / 147517.

[0052] According to the teachings of US Pat. No. 1,147,517, the coefficients of the filter 114 are obtained during a calibration performed by the biopotential recording unit 108 and are therefore specifically compensated for processing by the biopotential recording unit 108 .

[0053] The system of US11 / 147517 takes into account the components of the input path present during calibration: the input signal can be applied directly to the input of the device under test, or a circuit that is the electrical equivalent of an average or worst case lead set can be inserted before the input of the device under test.

[0054] The method of US 11 / 147517 does not take into account the fact that individual lead sets may behave differently. Calibration and correction based on this method is most effective in practice when the recording device is used with a lead set having characteristics similar to the simulation circuit used during calibration. The more different the behavior of the lead set used is from that of the simulation circuit, the less effective the correction will be in practice.

[0055] The present invention aims to address the blind spot of different readset behavior.

[0056] Because the present invention provides stored correction information as part of the leadset, a leadset system can be defined taking into account the leadset and the correction information, which is for delivering signals to a biopotential recording unit (e.g., an ECG device). The correction information is for use in processing the input channels, thereby improving channel symmetry, and relates only to the electrical characteristics of the leadset alone.

[0057] The leads 106 may be connected directly to the biopotential recording unit via a connector, however, Figure 2 shows an example of a lead set having multiple sections between the electrodes 104 and the biopotential recording unit 108.

[0058] The leads 106 form a set (schematically represented at 120) of separate leads. The leads 106 of the set 120 connect to a trunk cable 130 for connection to a biopotential recording unit 108. Between the set of leads 120 and the trunk cable 130 is a trunk cable connector 132. Between the trunk cable 130 and the biopotential recording unit 108 is another connector 134.

[0059] The present invention makes use of stored correction information. In a first set of examples (FIGS. 3 and 4), the correction information is stored on one or more digital storage devices that form part of the readset.

[0060] 3 shows a lead set having a set 120 of individual leads 106 that connect to a trunk connector 132, which then connects to a trunk cable 130. The trunk cable 130 connects to an ECG unit 108 via a further connector 134.

[0061] The trunk connector 132 has a digital storage device 140 and the further connector 134 has a digital storage device 142 .

[0062] Thus, each portion of the lead set has corrective information regarding the characteristics of that portion of the lead set, whether that be the portion between the connectors at each end or the portion between the electrode and the (most distal) connector.

[0063] 4 shows a lead set having a set 120 of individual leads 106 that connect to a lead set connector 150, which in turn connects to an individual set of leads 120a. Then there is a trunk cable connector 132 that connects to a trunk cable 130, and a further connector 134 that connects to a biopotential recording unit 108.

[0064] Each of the three connectors has data storage: trunk connector 132 has storage device 140, further connector 134 has storage device 142, and leadset connector 150 has storage device 152.

[0065] The data stored on the three storage devices is accessible at the biopotential recording unit 108 by wired connections that run alongside the leads.

[0066] In another example (not shown), the separate leads can be connected directly to the ECG unit 108 via a single lead set connector, where there is only one storage device (due to the nature of the leads from the electrodes to the lead set connector).

[0067] Each section has its own storage device for storing correction information specific to that section.

[0068] The ground connection to this storage device is, as shown, within recording unit 108. In this example, the contents of the storage device are retrieved using an interface that requires only a combined power and data connection, and a ground connection. Other interfaces that use more connections are possible, as well as interfaces that do not require an electrical connection (e.g., NFC).

[0069] 5, the biopotential recording unit 108 accesses the correction information from the remote memory 160. There is a wireless communication system between the biopotential recording unit 108 and the remote memory 160.

[0070] The system of the present invention extends input channel calibration to the leadset prior to leadset use and provides leadset calibration as a separate function. Because leadsets change frequently, it is not desirable to store the correction information in the biopotential recording unit (e.g., ECG device 108) itself, but instead to associate the correction information with the leadset itself.

[0071] By compensating for possible differences between the leads, the symmetry of the channel is improved as described above, resulting in an improved common-mode rejection ratio of the recording system. Measurements are less susceptible to noise and artifacts due to common-mode signals or interference. Measurements that are resilient to interference and artifacts are more useful for diagnostic and treatment decisions. This improves patient outcomes and patient and staff experience.

[0072] According to a first set of examples, the calibration information can be stored in the leadset, and then when a new leadset is connected, the recording unit can read the information. The digital storage device, in the first set of examples, is preferably non-volatile memory incorporated into the leadset. This non-volatile memory is used to store calibration information specific to each individual leadset. The contents of the digital storage device can be accessed by the biopotential recording unit via a wired connection (e.g., UART, I2C, SPI, 1WIRE, etc.) as described above, although a wireless (e.g., NFC) connection can also be used.

[0073] The correction information allows the recording unit to improve channel symmetry, i.e., compensate for input channel asymmetry caused by different transfer functions of the leads of the leadset. This correction information is generated during leadset manufacturing and stored in a storage device. The correction information is generated, for example, by applying a calibration signal to the input side of the leadset and recording the resulting signal at the output side of the leadset. The behavior of each input channel is recorded, and from this recording, the correction information in the form of channel-specific digital filter coefficients is obtained. The recorded output signals are then processed into a set of digital filter coefficients that the biopotential recording unit applies to the input channel signals.

[0074] The biopotential recording unit (or lead set, in the case of a lead set incorporating an analog-to-digital converter) samples the input channels in a single-ended mode referenced to a stable internal reference, allowing a calibration to be applied to each input channel signal after the analog-to-digital sampling operation and before differences between individual input channels are calculated.

[0075] The storage device may include means for storing the correction information in encrypted form. For example, digital filter coefficients may be stored in encrypted form to ensure that these coefficients are only used by authorized recording devices. The biopotential recording unit includes means for decrypting the correction information (e.g., a private decryption key or means for authenticating the recording unit to the lead set). This ensures that only authorized biopotential recording units can use the correction information.

[0076] The storage device may also include means for cryptographic authentication of the lead set by the controller, which allows the biopotential recording unit to recognize authorized lead sets.

[0077] If the cable connecting the electrodes on the patient to the biopotential recording unit is composed of multiple individual segments connected in series (e.g., as shown in FIG. 3 ), e.g., in the form of a trunk cable and attached lead sets, any segment that significantly contributes to the asymmetry of the input channel has its own digital storage device containing correction information specific to that segment. Segments closer to the biopotential recording unit include a means for communicating with the digital storage devices of more distant segments, regardless of whether the closer segments include their own digital storage devices. This may take the form of a hot-swappable bus, such as 1-Wire, or daisy-chaining non-hot-swappable communication interfaces. The communication chain may use several communication interfaces, such as USB, to communicate with the digital storage device on the trunk cable, and 1-Wire for communication between the digital logic circuitry on the trunk cable and the attached lead sets. Communication between the trunk cable and the attached lead sets is relayed to the biopotential recording unit via the USB connection between the biopotential recording unit and the trunk cable.

[0078] In a system using remote storage of correction information (FIG. 5), each lead set carries a unique identifier that can be digitally read and associated with corresponding correction information in a database. Upon connection of a lead set, the biopotential recording unit reads the unique identifier and uses it to retrieve the set of digital filter coefficients associated with the lead set from the database over a network connection. This method requires connecting the biopotential recording unit to a network that includes a database server.

[0079] As described above, the filter coefficients are used as part of the digital sampling of the analog signals collected by the electrodes. The filter coefficients define a digital filter for the electrode channel input. The resulting filter minimizes the time-domain difference between the signal of each input channel and the desired response. Furthermore, as a result of applying a filter to each electrode channel, common-mode interference signals can be more easily mitigated and / or canceled.

[0080] Digital filtering is performed by a correction filter to perform the correction function after A / D conversion / sampling. Digital filtering does not necessarily have to be the first processing step after A / D conversion; other determined digital filters may be applied first.

[0081] If the leadset input paths include a simple time delay, the optimization process generates filter coefficients that implement the time delay so that the overall delay of each channel after correction is as similar as possible.

[0082] In reality, the situation is more complicated, as the (linear) behavior of each input channel is described by its transfer function, which, as an approximation, gives the phase shift (delay) and gain for each frequency. Different frequencies are therefore delayed by different durations and attenuated by different factors.

[0083] The basic form of the transfer function is given by an electrical circuit or an appropriate model: the more complex the transfer function, the more filter coefficients the correction filter needs to achieve sufficient correction.

[0084] The optimization-based approach can compensate for any kind of linear behavior. Linear transfer functions can be used with any complexity. However, most cables can be modeled with fairly simple transfer functions.

[0085] The present invention can be applied to biopotential recording systems, such as electrocardiographs, electroencephalographs, or multiparameter patient monitors, and allows for improved performance of patient monitors and other electrophysiological recording devices when using improved leadset systems.

[0086] FIG. 6 illustrates a method for processing signals received from a leadset.

[0087] In step 200, signals are received from leads of a leadset, each lead defining an input channel.

[0088] In step 202, stored, optionally encrypted, determined correction information for the leads of the leadset, such as the digital filter coefficients described above, is accessed.

[0089] In step 204, the input channels are processed using the stored correction information, thereby improving the symmetry of the channels.

[0090] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, nor does it exclude a plurality of elements or steps if a plurality is not stated.

[0091] The functions performed by a processor may be implemented by a single processor or by multiple separate processing units which together may constitute a “processor.” Such processing units may be remote from each other and may communicate with each other via wired or wireless means.

[0092] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0093] The computer program may be stored / distributed on a suitable medium, for example an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, for example via the Internet or other wired or wireless telecommunications systems.

[0094] It should be noted that when the term "adapted for" is used in the claims or the specification, the term "adapted for" is intended to be synonymous with the term "configured to." When the term "apparatus" is used in the claims or the specification, the term "apparatus" is intended to be synonymous with the term "system," and vice versa.

[0095] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. 1. A lead set system for delivering signals to a biopotential recording unit, comprising: a leadset having a plurality of leads, each lead defining an input channel to a biopotential recording unit; stored correction information for the plurality of leads for use in processing the input channels, whereby channel symmetry is improved; and and A leadset system, wherein the correction information is associated with the leadset and is determined independently of the use or intended use of the leadset.

2. The leadset system of claim 1 , wherein the correction information comprises digital filter coefficients.

3. The lead set system according to claim 1 , wherein the correction information is encrypted.

4. The leadset system of claim 1 , wherein the stored correction information is located remotely from the leadset.

5. The leadset system of claim 1 , wherein the leadset comprises a digital storage device for storing the correction information.

6. The leadset system of claim 5 , wherein the digital storage device comprises a non-volatile memory.

7. The lead set system of claim 5 or 6, further comprising a connector for connecting the lead to a biopotential recording unit, the connector comprising the digital storage device.

8. 8. The lead set system of claim 7, further comprising a trunk cable for connecting to the biopotential recording unit, the connector comprising a trunk cable connector between the leads of the lead set and the trunk cable.

9. a lead set connector to which the leads of the lead set are connected; a set of intermediate leads between the lead set connector and the trunk cable connector; 9. The lead set system of claim 8, further comprising: a digital storage device connected to said lead set connector;

10. The lead set system according to any one of claims 1 to 9; a biopotential recording unit; wherein the biopotential recording unit is configured to read the stored correction information and improve channel symmetry.

11. 11. The system of claim 10, wherein the biopotential recording unit includes a digital filter, and the biopotential recording unit is configured to use the correction information to set the digital filter for each lead of the lead set.

12. 12. The system of claim 10 or 11, wherein the biopotential recording unit or the lead set comprises an analog-to-digital converter for each lead of the lead set, the analog-to-digital converter configured to sample the signal of each lead in a single-ended mode referenced to a reference.

13. 13. The system of claim 10, wherein the biopotential recording unit comprises a decryption system for decrypting the encrypted correction information.

14. 1. A method for processing a signal received from a leadset, comprising: receiving signals from leads of a leadset, each lead defining an input channel; accessing stored correction information for the leads of the readset, the correction information being associated with the readset and determined independent of the use or intended use of the readset; processing the input channels using the stored correction information, thereby improving channel symmetry; and A method comprising:

15. 15. A computer program having computer program code adapted to perform the method of claim 14 when the computer program is run on a computer.

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