Impedance measurement method, implantable medical device and implantable medical system

Abstract

The invention discloses an impedance measurement method, an implantable medical device and an implantable medical system. The impedance measurement method comprises the following steps: determining an expected interval of a current value applied to an electrode contact combination according to an electrode identifier of an electrode and the currently measured electrode contact combination; releasing measurement voltage to the electrode contact combinations and collecting current values between the electrode contact combinations; when the current value is not in the current value expected interval, adjusting the measurement voltage according to the current value; and when the current value is in a current value expected interval, determining an impedance value between the currently measured electrode contact combination according to the measured voltage and the current value. The accuracy of an impedance measurement result can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of implantable medical treatment, and in particular to an impedance measurement method, an implantable medical device and an implantable medical system. Background Art

[0002] After the electrodes of an implantable medical device are implanted in the brain, it is necessary to determine the connectivity of the in vivo conductive pathway (determine whether there is a short circuit or open circuit) by measuring the impedance of the biological tissue between the electrode contacts; if a short circuit occurs in the in vivo conductive pathway where the electrode contacts are located, the electrical stimulation output by the in vivo conductive pathway may generate excessive current, which may cause damage to the biological tissue receiving the specific stimulation or the tissue directly contacting the electrode contacts at the short circuit; if an open circuit occurs in the in vivo conductive pathway where the electrode contacts are located, the electrical stimulation output by the in vivo conductive pathway will not be transmitted to the target area, but will be directly output at the electrode contacts at the open circuit, and thus will not be able to produce effective treatment for the target biological tissue; in order to avoid connectivity failures such as short circuits or open circuits in the in vivo conductive pathway where the electrode contacts of the implantable medical device are located, thereby causing adverse effects such as ineffective treatment, it is very important to perform impedance measurement and detection of the electrode contacts of the implantable medical device.

[0003] The existing impedance measurement method for implantable medical devices adopts a constant voltage measurement method. For example, a fixed measurement voltage is applied to the object under test between the electrode contacts, and an analog-to-digital converter (ADC) is used to collect the current value between the electrode contacts. The ratio of the fixed voltage value to the collected current value is the impedance value of the biological tissue between the electrode contacts. However, since implantable medical devices may be equipped with different types of electrodes, the physical properties of different types of electrodes and electrode contact combinations are uncertain, it is impossible to obtain accurate impedance measurement results. Summary of the invention

[0004] The invention provides an impedance measurement method, an implantable medical device and an implantable medical system, which can improve the accuracy of impedance measurement results.

[0005] In a first aspect, an embodiment of the present invention provides an impedance measurement method for measuring the impedance between at least one electrode contact combination in at least one electrode implanted in a patient's body, the impedance measurement method comprising: determining an expected range of current values ​​applied to the electrode contact combination based on an electrode identifier of the electrode and a currently measured electrode contact combination; releasing a measurement voltage to the electrode contact combination and collecting the current value between the electrode contact combination; when the current value is not in the expected range of current values, adjusting the measurement voltage based on the current value; when the current value is in the expected range of current values, determining the impedance value between the currently measured electrode contact combination based on the measurement voltage and the current value.

[0006] Optionally, the step of determining an expected range of current values ​​applied to an electrode contact combination based on the electrode identification of the electrode and the currently measured electrode contact combination includes: determining the distance between the electrode contacts in the electrode based on the electrode identification; determining the resistance value range between the currently measured electrode contact combination based on the distance between the electrode contacts; and determining the expected range of current values ​​applied to the electrode contact combination based on the measured voltage and the resistance value range between the currently measured electrode contact combination.

[0007] Optionally, when the current value is not in the expected current value range, the step of adjusting the measurement voltage according to the current value includes: if the current value is less than the lower limit of the expected current value range, increasing the measurement voltage; if the current value is greater than the upper limit of the expected current value range, reducing the measurement voltage.

[0008] Optionally, if the current value is less than the lower limit value of the expected current value interval, the step of increasing the measurement voltage includes: if the current value is less than the lower limit value of the expected current value interval, determining the amplitude of each increase in the measurement voltage according to the degree of deviation between the current value and the lower limit value of the expected current value interval; and / or, if the current value is greater than the upper limit value of the expected current value interval, the step of reducing the measurement voltage includes: if the current value is greater than the upper limit value of the expected current value interval, determining the amplitude of each decrease in the measurement voltage according to the degree of deviation between the current value and the upper limit value of the expected current value interval.

[0009] Optionally, before the step of determining an expected interval of current values ​​applied to the electrode contact combination according to the electrode identifier of the electrode and the electrode contact combination currently measured, the impedance measurement method further includes: determining an initial measurement voltage according to the electrode identifier.

[0010] Optionally, after the steps of releasing the measurement voltage to the electrode contact combination and collecting the current value between the electrode contact combination, the impedance measurement method further includes: adding the number of measurements each time the measurement voltage is adjusted; in response to the number of measurements being less than or equal to a preset number of measurements, adjusting the measurement voltage according to the current value; in response to the number of measurements being greater than a preset number of measurements, determining the impedance value between the electrode contact combination currently being measured based on the measurement voltage and the current value.

[0011] Optionally, before the step of determining an expected range of current values ​​applied to the electrode contact combination according to the electrode identifier of the electrode and the electrode contact combination currently measured, the impedance measurement method further includes: determining a preset number of measurements according to the electrode identifier.

[0012] Optionally, after the step of determining the impedance value between the electrode contact combination currently being measured based on the measured voltage and the current value when the current value is in the expected current value range, the impedance measurement method further includes: when all electrode contact combinations on the electrode currently being measured have been measured, determining whether the measurement of other electrodes has been completed; when all electrode contact combinations on the electrode currently being measured have not been measured, returning to continue executing the step of determining the expected current value range applied to the electrode contact combination based on the electrode identification of the electrode and the electrode contact combination currently being measured.

[0013] Optionally, when all electrode contact combinations on the currently measured electrode have been measured, the step of determining whether other electrodes have been measured includes: when other electrodes have not been measured, determining the initial measurement voltage according to the electrode identifier; when other electrodes have been measured, ending the measurement.

[0014] Optionally, the electrode identification includes at least the type of electrode contacts in the electrode and the distance between the electrode contacts.

[0015] In a second aspect, an embodiment of the present invention provides an implantable medical device, which is connected to an electrode implanted in a target point of a patient, and includes a processing circuit; the processing circuit includes at least an ADC sampling module and a voltage regulating module, and the ADC sampling module and the voltage regulating module are both connected to the electrode, and the voltage regulating module is configured as at least the impedance measurement method provided by any embodiment of the present invention.

[0016] In a third aspect, an embodiment of the present invention provides an implantable medical system, including the implantable medical device provided by the embodiment of the present invention, and also including electrodes, the implantable medical device being connected to the electrodes for measuring the impedance between at least one electrode contact combination in at least one electrode.

[0017] The impedance measurement method provided by the embodiment of the present invention determines the expected range of current values ​​applied to the electrode contact combination according to the electrode identifier and the electrode contact combination currently measured, and can preset a reasonable expected range of current values ​​for the characteristics of different types of electrodes and the electrode contact combination currently measured. During the measurement process, the measurement voltage can be adjusted according to the actual conditions of different contact combinations to ensure that the measurement results accurately reflect the impedance of the measured body between different electrode contact combinations. For example, if the current value is less than the lower limit of the expected range of current values ​​under the current measurement voltage, the measurement voltage is increased; if the current value is greater than the upper limit of the expected range of current values ​​under the current measurement voltage, the measurement voltage is reduced, so that the measurement result is closer to the true impedance value, the error caused by fixed measurement conditions is reduced, the measurement accuracy is improved, and the impedance measurement range of implantable medical devices with different electrode identifiers is expanded. Accurate impedance measurement helps to optimize the parameter settings of implantable medical devices, such as adjusting the output power of cardiac pacemakers, the stimulation pulse parameters of deep brain stimulators, etc.

[0018] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 is a flow chart of an impedance measurement method provided by an embodiment of the present invention;

[0021] Figure 2a is a flow chart of another impedance measurement method provided by an embodiment of the present invention;

[0022] Figure 2b is a flow chart of another impedance measurement method provided by an embodiment of the present invention;

[0023] Figure 3 is a flow chart of another impedance measurement method provided by an embodiment of the present invention;

[0024] Figure 4 is a flow chart of another impedance measurement method provided by an embodiment of the present invention;

[0025] Figure 5 is a flow chart of another impedance measurement method provided by an embodiment of the present invention;

[0026] Figure 6 is a flow chart of another impedance measurement method provided by an embodiment of the present invention;

[0027] Figure 7 It is a structural schematic diagram of an implantable medical device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0029] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0030] Figure 1 The present invention provides a flowchart of an impedance measurement method provided by an embodiment of the present invention. The impedance measurement method is used to measure the impedance of biological tissue between at least one electrode contact combination in at least one electrode implanted in a patient's body.

[0031] An implantable medical device is an implantable, programmable, multi-program medical device, which may be any one of an implantable neural stimulation device, an implantable cardiac stimulation system (also known as a pacemaker), an implantable drug delivery system (IDDS), and a lead switching device. Examples of implantable neural stimulation devices include a deep brain stimulation system (DBS), an implantable cortical nerve stimulation system (CNS), an implantable spinal cord stimulation system (SCS), an implantable sacral nerve stimulation system (SNS), an implantable vagus nerve stimulation system (VNS), and the like.

[0032] The implantable neural electrical stimulation system includes a stimulator implanted in the patient's body (i.e., an implantable neural stimulator) and a programmable device disposed outside the patient's body. In other words, the stimulator is a medical device, or in other words, the medical device includes the stimulator. The relevant neural regulation technology mainly implants electrodes (electrodes, for example, in the form of electrode wires) in specific parts of the tissues of the organism (i.e., target points) through stereotactic surgery, and emits discharge pulses to the target points through the electrodes to regulate the electrical activity and function of the corresponding neural structures and networks, thereby improving symptoms and relieving pain.

[0033] As an example, DBS includes an implantable pulse generator (IPG), an extension lead and an electrode lead, and the IPG is connected to the electrode lead via the extension lead. The IPG is implanted in the patient's body, for example, in the patient's chest or other body parts.

[0034] As another example, DBS includes an IPG and an electrode lead, and the IPG is directly connected to the electrode lead. The IPG is implanted in the patient's head, for example, a groove is made in the patient's skull, and then the IPG is installed in the groove of the skull. In this case, the IPG may not protrude from the outer surface of the skull, or may partially protrude from the outer surface of the skull.

[0035] The IPG responds to the program-controlled instructions sent by the program-controlled device, and relies on sealed batteries and circuits to provide controllable electrical stimulation therapy (or electrical stimulation energy) to the tissues in the body. The IPG delivers one or more controllable specific electrical stimulations to specific areas of the tissues in the body through electrode wires.

[0036] In some embodiments, the extension lead is used in conjunction with the IPG as a transmission medium for electrical stimulation, and transmits the electrical stimulation generated by the IPG to the electrode lead.

[0037] In some embodiments, the electrical stimulation may be delivered in the form of a pulse signal or in the form of a non-pulse signal. For example, the electrical stimulation may be delivered as a signal having various waveform shapes, frequencies, and amplitudes. Thus, the electrical stimulation in the form of a non-pulse signal may be a continuous signal, which may have a sinusoidal waveform or other continuous waveform.

[0038] After receiving the electrical stimulation transmitted by the IPG or the extension wire, the electrode wire delivers the electrical stimulation to a specific area of ​​the tissue in the body through a plurality of electrode contacts. The stimulator is provided with, for example, one or more electrode wires on one side or both sides, and a plurality of electrode contacts are provided on the electrode wire, and the electrode contacts can be arranged uniformly or non-uniformly in the circumferential direction of the electrode wire. As an example, the electrode contacts can be arranged in an array of 4 rows and 3 columns (a total of 12 electrode contacts) in the circumferential direction of the electrode wire. The electrode contacts can include stimulation electrode contacts and / or collection electrode contacts. The electrode contacts can be in the shape of sheets, rings, dots, etc., for example.

[0039] In some embodiments, the stimulated body tissue may be the patient's brain tissue, and the stimulated site may be a specific site of the brain tissue. When the patient's disease type is different, the stimulated site is generally different, and the number of stimulation contacts (single source or multiple sources), the use of one or more (single channel or multiple channels) of specific electrical stimulation, and the stimulation parameters (values) are also different.

[0040] The embodiments of the present invention do not limit the types of diseases that can be used, and can be diseases that can be used for deep brain stimulation (DBS), spinal cord stimulation (SCS), sacral nerve stimulation, gastric stimulation, peripheral nerve stimulation, and functional electrical stimulation. Among them, DBS can be used to treat or manage diseases including, but not limited to: spastic diseases (e.g., epilepsy), pain, migraine, mental illness (e.g., major depressive disorder (MDD)), bipolar disorder, anxiety, post-traumatic stress disorder, mild depression, obsessive-compulsive disorder (OCD), behavioral disorders, mood disorders, memory disorders, mental state disorders, movement disorders (e.g., essential tremor or Parkinson's disease), Huntington's disease, Alzheimer's disease, drug addiction, autism or other neurological or psychiatric diseases and injuries.

[0041] In an embodiment of the present invention, when a programmable connection is established between a programmable device and a stimulator, the programmable device can be used to adjust one or more stimulation parameters of the stimulator (or one or more stimulation parameters of a pulse generator, and different stimulation parameters correspond to different electrical stimulations), or the stimulator can sense the patient's electrophysiological activities to collect electrophysiological signals, and the collected electrophysiological signals can be used to continue to adjust the stimulation parameters of the stimulator, thereby realizing closed-loop control (or adaptive adjustment) of the stimulation parameters.

[0042] The stimulation parameters may include at least one of the following: the electrode contact identification used to deliver electrical stimulation (for example, electrode contact #2 and electrode contact #3), frequency (for example, the number of electrical stimulation pulse signals within a unit time of 1s, in Hz), pulse width (the duration of each pulse, in μs), amplitude (generally expressed in voltage, that is, the intensity of each pulse, in V), timing (for example, it can be continuous or burst, and burst refers to discontinuous timing behavior composed of multiple processes), stimulation mode (including one or more of current mode, voltage mode, timed stimulation mode and cyclic stimulation mode), upper and lower limits controlled by the doctor (the range that can be adjusted by the doctor) and upper and lower limits controlled by the patient (the range that can be adjusted autonomously by the patient).

[0043] In some embodiments, various stimulation parameters of the stimulator can be adjusted in current mode or voltage mode.

[0044] Programmable devices may include doctor programmable devices (i.e. programmable devices used by doctors) and / or patient programmable devices (i.e. programmable devices used by patients). Doctor programmable devices are, for example, tablet computers, laptop computers, desktop computers, mobile phones and other intelligent terminal devices equipped with programmable software. Patient programmable devices are, for example, tablet computers, laptop computers, desktop computers, mobile phones and other intelligent terminal devices equipped with programmable software. Patient programmable devices may also be other electronic devices with programmable functions (e.g., chargers with programmable functions, electrophysiological acquisition devices, etc.).

[0045] The method of the embodiment of the present invention can be performed by an implantable medical device (i.e., a pulse generator). Figure 1 As shown, the impedance measurement method includes:

[0046] S101 . Determine an expected range of current values ​​applied to an electrode contact combination according to an electrode identifier of an electrode and a currently measured electrode contact combination.

[0047] Specifically, the electrode identifier is an identifier used to distinguish different types of electrodes. Different types of electrodes differ in the number of electrode contacts. For example, some electrodes may have only two electrode contacts, which are suitable for simple stimulation or measurement scenarios, such as some basic neural stimulation electrodes; while other electrodes may have 8 or even more electrode contacts, like deep brain stimulation electrodes for complex neural regulation. Multiple electrode contacts can provide more flexible stimulation mode selection, which can accurately act on neural tissue in different areas or depths. The distribution of electrode contacts on the electrodes is different. Taking a cylindrical electrode as an example, its electrode contacts may be distributed in a complete ring shape, which can provide a more uniform stimulation or measurement effect in the circumferential direction when the current is conducted; it may also be distributed in a partial arc shape, such as a 120-degree arc.

[0048] The electrode contact combination currently measured refers to any two electrode contacts on one side of the electrode when performing impedance measurement. In implantable medical devices, electrodes usually contain multiple electrode contacts, and each measurement is performed only on specific two electrode contacts. For electrodes with multiple electrode contacts (such as n), the number of electrode contact combinations can be obtained by the combination formula For example, an electrode with 4 electrode contacts (labeled A1, A2, A3 and A4) has a combination of electrode contacts. There are three types, namely A1A2, A1A3, A1A4, A2A3, A2A4 and A3A4.

[0049] Different electrode contact combinations can reflect the impedance of different areas of the subject. Taking the nerve stimulation electrode as an example, the adjacent electrode contact combination (such as A1A2) measures the impedance of the subject in a relatively small area near the electrode, which helps to understand the characteristics of the local neural tissue; while the electrode contact combination with a larger spacing (such as A1A4) measures the comprehensive impedance of a larger range of tissues, which can provide information about the overall electrical properties of the neural pathway or tissue. By measuring a variety of electrode contact combinations, a more comprehensive understanding of the impedance distribution of the subject at different locations and scales can be obtained, which is crucial for accurately evaluating the interaction between implantable medical devices (i.e., pulse generators) and the subject (such as the patient's target point where the electrode is implanted) and optimizing device parameters. Usually, each electrode contact combination is measured in sequence. This order can be pre-set, for example, starting from adjacent electrode contact combinations and gradually transitioning to combinations with a larger spacing, which helps to systematically understand the impedance change law of the subject from local to overall.

[0050] Optionally, when multiple electrodes are implanted deep in the patient's brain, when measuring the impedance value, any two electrode contacts on one side of the electrode can be selected for measurement, thereby enabling targeted measurement of the electrode contacts that require impedance measurement, thereby improving measurement efficiency; in addition, when troubleshooting electrode contact failures, regular arrangements and combinations of electrode contacts can be selected for measurement to achieve the purpose of accurate troubleshooting.

[0051] The expected current value range refers to a reasonable current value range that is pre-set based on the electrode identification and the electrode contact combination currently being measured when measuring the impedance of an implantable medical device. This range is based on the understanding of the characteristics of the electrode and the measured object, and is the range in which the current value is expected to be under ideal measurement conditions.

[0052] In some embodiments, different electrode identifiers have different contact numbers and distribution patterns. For example, for an electrode identifier with 8 contacts and dense distribution, the current conduction path is relatively complex and short; while for an electrode identifier with 4 contacts and sparse distribution, the current conduction path is relatively simple but long. Based on this information, a preliminary estimate of the ease of current conduction for different electrode identifiers under the same measurement voltage can be made. Electrodes with many and dense contacts may be more likely to form a current path during measurement, and the expected current value is relatively large; while electrodes with few and sparse contacts have relatively limited current paths, and the expected current value is smaller.

[0053] Furthermore, the distance between the electrode contacts is accurately calculated based on the electrode contact combination currently measured. According to the law of resistance, the larger the distance between the electrode contacts, the greater the resistance, and the smaller the current at a fixed measurement voltage. For example, for adjacent contact combinations, the resistance value is small when the distance is close, and the expected current value is large; the resistance of the contact combination with a large spacing is large, and the expected current value is small. By accurately calculating the distance relationship between different electrode contact combinations, the general trend of the current value changing with the contact combination can be preliminarily determined, that is, the current value gradually decreases when the distance increases.

[0054] The expected range of current values ​​is obtained by calculating and analyzing the electrode identification and electrode contact combination. For example, for a specific electrode identification and electrode contact combination, a basic resistance range is estimated based on the electrode contact distance and distribution, and then the current value is calculated using Ohm's law (assuming the measured voltage is known) to determine the upper and lower limits of the expected range of current values.

[0055] S102: releasing a measurement voltage to the electrode contact combination and collecting a current value between the electrode contact combination.

[0056] Specifically, the voltage is released from a preset initial measurement voltage. This initial measurement voltage is determined according to the electrode identifier. For electrode identifiers with dense distribution of electrode contacts and small expected impedance, a lower initial measurement voltage is usually set; and for electrode identifiers with sparse distribution of electrode contacts and large expected impedance, a higher initial measurement voltage is set. For example, for an electrode identifier with 8 contacts and dense distribution, the initial measurement voltage may be set to 1V; and for an electrode identifier with only 4 contacts and a more dispersed distribution, the initial measurement voltage may be set to 5V.

[0057] When the measurement voltage is stably applied to the electrode contact combination, the current value is immediately collected. The collection process requires the use of a highly sensitive and high-precision current collection device that can quickly and accurately obtain the current flowing between the electrode contacts. For example, the high-precision ADC in the pulse generator converts the analog current signal into a digital signal for subsequent processing.

[0058] S103: Determine whether the current value is within an expected current value range.

[0059] Specifically, when the current value is not in the expected current value interval, the measurement voltage is adjusted according to the current value. When the current value is in the expected current value interval, the impedance value between the electrode contact combination currently measured is determined according to the measurement voltage and the current value. That is, when the current value is not in the expected current value interval, step S104 is executed; when the current value is in the expected current value interval, step S105 is executed.

[0060] S104. Adjust the measurement voltage according to the current value.

[0061] In some embodiments, when it is determined that the current value is less than the lower limit of the expected current value interval, the measurement voltage is increased. If the current value is greater than the upper limit of the expected current value interval, the measurement voltage is reduced. It is understandable that after adjusting the measurement voltage, it is necessary to return to the step of releasing the measurement voltage and collecting the current value, that is, return to step S102.

[0062] S105: Determine the impedance value between the electrode contact combination currently being measured according to the measured voltage and current values.

[0063] Specifically, when the current value is within the expected current value range, the impedance value of the biological tissue between the current electrode contact combination is accurately calculated using Ohm's law based on the measured voltage and current value at this time.

[0064] The impedance measurement method provided by the embodiment of the present invention determines the expected current value interval according to the electrode identifier and the electrode contact combination currently measured, and can preset a reasonable expected current value interval for the characteristics of different types of electrodes and the electrode contact combination currently measured. During the measurement process, the measurement voltage can be adjusted according to the actual conditions of different contact combinations to ensure that the measurement results accurately reflect the impedance of the measured object between different electrode contact combinations. For example, if the current value is less than the lower limit of the expected current value interval under the current measurement voltage, the measurement voltage is increased; if the current value is greater than the upper limit of the expected current value interval under the current measurement voltage, the measurement voltage is reduced, so that the measurement result is closer to the true impedance value, the error caused by fixed measurement conditions is reduced, the measurement accuracy is improved, and the impedance measurement range of implantable medical devices with different electrode identifiers is expanded. Accurate impedance measurement helps to optimize the parameter settings of implantable medical devices, such as adjusting the output power of cardiac pacemakers, the stimulation pulse parameters of deep brain stimulators, etc.

[0065] Figure 2a FIG. 1 is a flow chart of another impedance measurement method provided by an embodiment of the present invention. Figure 2a As shown, the impedance measurement method includes:

[0066] S110, determining the distance between electrode contacts in the electrode according to the electrode identifier.

[0067] Specifically, the manufacturer usually provides detailed design documents of the electrode, which contain the layout information of the electrode contacts. If the electrodes are arranged according to a standard geometric pattern, such as a rectangular array, a circular array, etc., the distance between the electrode contacts can be determined according to the parameters in the document.

[0068] For example, for a circular array electrode design, the document may give the radius r of the circle and the central angle θ between adjacent contacts. If you want to calculate the arc length distance (the distance along the circumference) between two contacts, you can use the arc length formula l = rθ. If you want to calculate the straight-line distance, you can use trigonometric functions to calculate the triangle formed by the center of the circle and the two contacts.

[0069] S120: Determine the resistance value range between the electrode contact combinations currently being measured according to the distance between the electrode contacts.

[0070] Specifically, the resistance law is Where R is the resistance, ρ is the resistivity (related to the electrode material), l1 is the distance between the electrode contacts (that is, the length of the path through which the current passes), and S is the cross-sectional area of ​​the electrode contacts (related to the physical structure of the electrode).

[0071] First, the resistivity ρ must be determined. This can be obtained by consulting a manual on the physical properties of the electrode material or from the technical specification document provided by the electrode manufacturer. For example, common electrode materials such as platinum have a resistivity of about 10.6×10 -8 Ω·m.

[0072] Then determine the cross-sectional area S of the electrode contact. If the electrode is a cylindrical contact, its cross-sectional area S = πr 2 , where r is the radius of the cylindrical contact. This radius can be obtained through the design parameters of the electrode or actual measurement. For non-cylindrical contacts, the cross-sectional area can also be calculated based on the area formula corresponding to its geometric shape.

[0073] After the resistivity ρ and the cross-sectional area S are determined, the resistance value is calculated based on the distance l1 between the electrode contacts. Since the distance between the electrode contacts may be a range (for example, the minimum distance is l 1min , the maximum is l 1max ), then the resistance value range is

[0074] S130 : Determine an expected interval of current values ​​applied to the electrode contact combination according to the measured voltage and the resistance value range between the electrode contact combination currently measured.

[0075] Ohm's law is Where I is current, V is voltage, and R is resistance. First, determine the measurement voltage, which can be a preset fixed value.

[0076] The known resistance value range is [R min ,R max ], substituting it into Ohm's law, we can get the current value range This is the expected current range based on Ohm's law. For example, if the measured voltage V = 5V and the resistance range is [10Ω, 20Ω], then the expected current range is [0.25A, 0.5A].

[0077] S140: releasing a measurement voltage to the electrode contact combination and collecting a current value between the electrode contact combination.

[0078] S150: Determine whether the current value is within an expected current value range.

[0079] When the current value is not within the expected current value range, step S160 is executed; when the current value is within the expected current value range, step S170 is executed.

[0080] S160. Adjust the measurement voltage according to the current value.

[0081] After the measurement voltage is adjusted, it is necessary to return to the step of releasing the measurement voltage and collecting the current value, that is, return to step S140.

[0082] S170: Determine the impedance value between the electrode contact combination currently being measured according to the measured voltage and current values.

[0083] Figure 2b FIG. 1 is a flow chart of another impedance measurement method provided by an embodiment of the present invention. Figure 2b As shown, the impedance measurement method includes:

[0084] S201 . Determine an expected range of current values ​​applied to an electrode contact combination according to an electrode identifier of an electrode and a currently measured electrode contact combination.

[0085] S202: Release a measurement voltage to the electrode contact combination and collect a current value between the electrode contact combination.

[0086] S203: Determine whether the current value is within an expected current value range.

[0087] Specifically, when the current value is not within the expected current value range, step S204 is executed; when the current value is within the expected current value range, step S205 is executed.

[0088] S204 , if the current value is less than the lower limit of the expected current value interval, increase the measurement voltage; if the current value is greater than the upper limit of the expected current value interval, decrease the measurement voltage.

[0089] Specifically, when the current value is less than the lower limit of the expected current value range, it means that the current measurement voltage may be too low to accurately reflect the impedance characteristics of the measured object, and the measurement voltage needs to be increased to obtain a more accurate measurement result.

[0090] Optionally, if the current value is less than the lower limit of the expected current value interval, the amplitude of the measured voltage increased each time is determined according to the degree of deviation between the current value and the lower limit of the expected current value interval. An adjustment proportional coefficient can be set in advance. For example, when the current value is less than 10% of the lower limit, the measured voltage is increased by 5% each time; when the current value is 10% to 20% lower than the lower limit, it is increased by 10% each time; when the current value is more than 20% lower than the lower limit, it is increased by 20% each time, etc. In this way, the voltage is gradually increased, and the current value is continuously collected to observe whether the current value enters the expected current value interval. In the process of increasing the voltage, pay close attention to the changing trend of the current value to avoid the voltage increasing too fast, resulting in excessive current and damaging the equipment or causing adverse effects on the object being measured. It is also necessary to ensure that the measured voltage is always within the maximum voltage range allowed by the processing circuit, and at the same time, the tolerance of the object being measured to the current should be considered to prevent damage to the object being measured.

[0091] When the current value is greater than the upper limit of the expected current value range, it means that the current measurement voltage may be too high and cannot accurately reflect the impedance characteristics of the object being measured. The measurement voltage needs to be reduced to obtain a more accurate measurement result.

[0092] Optionally, if the current value is greater than the upper limit of the expected current value interval, the amplitude of the measured voltage reduction each time is determined according to the degree of deviation between the current value and the upper limit of the expected current value interval. An adjustment proportional coefficient can be pre-set, for example, when the current value is within 10% of the upper limit, the measured voltage is reduced by 3% each time; when the current value is 10% to 20% higher than the upper limit, it is reduced by 6% each time; when the current value is more than 20% higher than the upper limit, it is reduced by 10% each time, etc. After reducing the voltage, the current value is continuously collected to see if it returns to the expected current value interval. It should be noted that when reducing the voltage, the effectiveness of the measurement must also be ensured, and the voltage cannot be too low to accurately measure the impedance. At the same time, the normal operation of the equipment and the object to be measured must be guaranteed. When measuring different electrodes, a fixed measurement voltage may cause abnormal current values. By adjusting the measurement voltage according to the current value, the current value can be brought into the expected current value interval, thereby calculating a more accurate impedance value according to Ohm's law. This is crucial for accurately evaluating the interaction between implantable medical devices and the subject. For example, in a pacemaker, accurate impedance measurement helps optimize the pacemaker's output parameters to ensure that the heart receives appropriate electrical stimulation and maintains normal heart rhythm.

[0093] S205: Determine the impedance value between the electrode contact combination currently being measured according to the measured voltage and current values.

[0094] Figure 3 FIG. 1 is a flow chart of another impedance measurement method provided by an embodiment of the present invention. Figure 3 As shown, the impedance measurement method includes:

[0095] S301. Determine an initial measurement voltage according to an electrode identifier.

[0096] Specifically, different electrode markers have different numbers of contacts, and the distribution of electrode contacts on the electrodes is also different. For electrode markers with dense distribution of electrode contacts and small expected impedance, a lower initial measurement voltage can be set; while for electrode markers with sparse distribution of electrode contacts and large expected impedance, a higher initial measurement voltage can be set. For example, for an electrode marker with 8 contacts and dense distribution, the initial measurement voltage may be set to 1V; while for an electrode marker with only 4 contacts and a more dispersed distribution, the initial measurement voltage may be set to 5V. Accurately setting the initial measurement voltage can avoid measurement errors caused by excessively high or low voltage. If the initial measurement voltage is too high, the current may exceed the setting range of the pulse generator, causing the pulse generator to give an incorrect current value and unable to accurately calculate the impedance; if the initial measurement voltage is too low, an effective current path may not be formed, resulting in no current measurement or the measured current value is too small, and the impedance cannot be accurately calculated.

[0097] S302: Determine an expected range of current values ​​applied to the electrode contact combination according to the electrode identifier of the electrode and the electrode contact combination currently measured.

[0098] S303: Release the measurement voltage to the electrode contact combination and collect the current value between the electrode contact combination.

[0099] S304: Determine whether the current value is within an expected current value range.

[0100] Specifically, when the current value is not within the expected current value range, step S305 is executed; when the current value is within the expected current value range, step S306 is executed.

[0101] S305. Adjust the measurement voltage according to the current value.

[0102] S306: Determine the impedance value between the electrode contact combination currently being measured according to the measured voltage and current values.

[0103] Figure 4 FIG. 1 is a flow chart of another impedance measurement method provided by an embodiment of the present invention. Figure 4 As shown, the impedance measurement method includes:

[0104] S401. Determine a preset number of measurements according to the electrode identifier.

[0105] Specifically, different electrode markers differ in the number, distribution, and physical properties of electrode contacts. For example, an electrode marker with many densely distributed electrode contacts has a complex current conduction path, and more measurements may be required to obtain accurate impedance values ​​when measuring impedance. Taking an electrode marker with 8 closely arranged electrode contacts as an example, due to the complex conduction of current between multiple electrode contacts, more measurements may be required, such as a preset number of measurements of 15 times. For electrode markers with few and sparsely distributed electrode contacts, current conduction is relatively simple, and the preset number of measurements may be relatively small, such as 8 times.

[0106] Since implantable medical devices may be equipped with different types of electrodes, the physical properties of each electrode identifier and its electrode contacts are uncertain, as well as the physical properties of the measured object itself, various complex situations may be encountered during the measurement process. For example, in some extreme cases, even if the process of adaptively adjusting the measurement voltage is followed, the current value may not be able to enter the expected current value range. If the upper limit of the number of measurements is not set (that is, the preset number of measurements is not set), the pulse generator may keep trying to adjust the measurement voltage and collect, thus falling into an endless loop and causing the measurement to fail to complete normally. Setting the preset number of measurements ensures that even in unexpected situations, the pulse generator can stop measuring after a certain number of attempts, thereby ensuring the controllability of the measurement process.

[0107] Unexpected conditions are those that are beyond normal expectations and may interfere with the measurement process and cause the pulse generator to operate abnormally (such as falling into an infinite loop). For example, there may be manufacturing defects or specially designed electrodes with extremely high resistance between the electrode contacts, close to infinity. In this case, no matter how the measurement voltage is adjusted, according to Ohm's law, the current value may never reach the expected current value range. Because even if the measurement voltage is increased to the maximum value allowed by the device, the current is still very small due to the extremely large resistance, and the pulse generator will continue to judge that the current value is not in the expected current value range, and thus continue to try to adjust the voltage, falling into an infinite loop.

[0108] S402: Determine an expected range of current values ​​applied to the electrode contact combination according to the electrode identifier of the electrode and the electrode contact combination currently measured.

[0109] S403, clear the number of measurements.

[0110] Specifically, the purpose of clearing the number of measurements is to accurately record the number of each measurement, so as to ensure that the subsequent comparison with the preset number of measurements is accurate. Each time a new electrode contact combination measurement is started, counting starts from the initial state.

[0111] S404: Release the measurement voltage to the electrode contact combination and collect the current value between the electrode contact combination.

[0112] S405. Each time the measurement voltage is adjusted, the number of measurements is accumulated.

[0113] S406: Determine whether the current value is within an expected current value range.

[0114] Specifically, when the current value is not in the expected current value interval, it is determined whether the number of measurements is greater than the preset number of measurements, and when the current value is in the expected current value interval, the impedance value between the electrode contact combination currently measured is determined according to the measured voltage and the current value. That is, when the current value is not in the expected current value interval, step S407 is executed; when the current value is in the expected current value interval, step S409 is executed.

[0115] S407: Determine whether the number of measurements is greater than a preset number of measurements.

[0116] Specifically, in response to the number of measurements being less than or equal to the preset number of measurements, the measurement voltage is adjusted according to the current value. In response to the number of measurements being greater than the preset number of measurements, the impedance value between the electrode contact combination currently being measured is determined based on the measurement voltage and the current value. That is, when the number of measurements is less than or equal to the preset number of measurements, step S408 is executed; when the number of measurements is greater than the preset number of measurements, step S409 is executed.

[0117] S408. Adjust the measurement voltage according to the current value.

[0118] S409: Determine the impedance value between the electrode contact combination currently being measured according to the measured voltage and current values.

[0119] Figure 5 FIG. 1 is a flow chart of another impedance measurement method provided by an embodiment of the present invention. Figure 5 As shown, the impedance measurement method includes:

[0120] S501. Determine an initial measurement voltage according to an electrode identifier.

[0121] S502: Determine an expected range of current values ​​applied to the electrode contact combination according to the electrode identifier of the electrode and the electrode contact combination currently measured.

[0122] S503: Release the measurement voltage to the electrode contact combination and collect the current value between the electrode contact combination.

[0123] S504: Determine whether the current value is within an expected current value range.

[0124] Specifically, when the current value is not within the expected current value range, step S505 is executed; when the current value is within the expected current value range, step S506 is executed.

[0125] S505. Adjust the measurement voltage according to the current value.

[0126] S506: Determine the impedance value between the electrode contact combination currently being measured according to the measured voltage and current values.

[0127] S507: Determine whether all electrode contact combinations on the electrode currently being measured have been measured.

[0128] Specifically, there may be multiple electrode contact combinations on an electrode, and impedance measurements need to be performed on them in sequence. After completing the measurement of the current electrode contact combination, determine whether all combinations on the electrode have been measured. When all electrode contact combinations on the electrode currently being measured have been measured, determine whether the measurements of other electrodes have been completed. When all electrode contact combinations on the electrode currently being measured have not been measured, return to continue the step of determining the expected range of current values ​​based on the electrode identification of the electrode and the electrode contact combination currently being measured. That is, when all electrode contact combinations on the electrode currently being measured have been measured, execute step S508; when all electrode contact combinations on the electrode currently being measured have not been measured, execute step S502.

[0129] S508: Determine whether the measurement of other electrodes has been completed.

[0130] Specifically, if there are other electrodes that need to be measured, the initial measurement voltage is determined according to the electrode identification, and the measurement of the next electrode is started, and the entire measurement process is repeated. This ensures comprehensive measurement of all electrodes and can obtain more complete impedance information. When all electrodes are measured, the measurement process ends. That is, if the measurement of other electrodes has not been completed, return to execute S501; if the measurement of other electrodes has been completed, execute S509.

[0131] S509: End the measurement.

[0132] Figure 6 FIG. 1 is a flow chart of another impedance measurement method provided by an embodiment of the present invention. Figure 6 As shown, the impedance measurement method includes:

[0133] S601. Determine an initial measurement voltage and a preset number of measurements according to an electrode identifier.

[0134] S602: Determine an expected range of current values ​​applied to the electrode contact combination according to the electrode identifier of the electrode and the electrode contact combination currently measured.

[0135] S603, clear the number of measurements.

[0136] S604: Release the measurement voltage to the electrode contact combination and collect the current value between the electrode contact combination.

[0137] S605. Each time the measurement voltage is adjusted, the number of measurements is accumulated.

[0138] S606, determine whether the current value is within the expected current value range.

[0139] When the current value is not within the expected current value range, step S607 is executed; when the current value is within the expected current value range, step S609 is executed.

[0140] S607: Determine whether the number of measurements is greater than a preset number of measurements.

[0141] When the number of measurements is less than or equal to the preset number of measurements, step S608 is executed; when the number of measurements is greater than the preset number of measurements, step S609 is executed.

[0142] S608. Adjust the measurement voltage according to the current value.

[0143] S609: Determine the impedance value between the electrode contact combination currently being measured according to the measured voltage and current values.

[0144] S610: Determine whether all electrode contact combinations on the electrode currently being measured have been measured.

[0145] When all electrode contact combinations on the electrode currently being measured have been measured, step S611 is executed; when all electrode contact combinations on the electrode currently being measured have not been measured, the process returns to step S602.

[0146] S611, determine whether the measurement of other electrodes is completed.

[0147] When the measurement of other electrodes has not been completed, the process returns to S601 ; when the measurement of other electrodes has been completed, the process proceeds to S612 .

[0148] S612: End measurement.

[0149] Based on the same inventive concept, an embodiment of the present invention also provides an implantable medical device. Figure 7 FIG. 1 is a schematic diagram of the structure of an implantable medical device provided by an embodiment of the present invention. Figure 7As shown, the implantable medical device 1 is connected to the electrode 2 implanted in the target point of the patient, and the implantable medical device 1 includes a processing circuit 11; the processing circuit 11 includes at least an ADC sampling module 111 and a voltage regulating module 112, and the ADC sampling module 111 and the voltage regulating module 112 are both connected to the electrode 2, and the voltage regulating module 112 is configured to at least execute the impedance measurement method provided by any embodiment of the present invention. The implantable medical device provided by the embodiment of the present invention has the beneficial effects of the impedance measurement method provided by the embodiment of the present invention. For details, please refer to the specific description of the impedance measurement method in the above embodiments, and this embodiment will not be repeated here.

[0150] An embodiment of the present invention further provides an implantable medical system, comprising the implantable medical device provided in the above embodiment, and further comprising electrodes, wherein the implantable medical device is connected to the electrodes and is used to measure the impedance between at least one electrode contact combination in at least one electrode.

[0151] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An impedance measurement method, characterized in that: The impedance measurement method is used to measure the impedance between at least one electrode contact combination in at least one electrode implanted in a patient, the impedance measurement method comprising: Determining an expected interval of current values ​​applied to the electrode contact combination according to the electrode identifier of the electrode and the electrode contact combination currently measured; releasing a measurement voltage to the electrode contact combination and collecting a current value between the electrode contact combination; When the current value is not within the expected current value interval, adjusting the measurement voltage according to the current value; When the current value is within the expected current value interval, the impedance value between the electrode contact combination currently being measured is determined according to the measured voltage and the current value.

2. The impedance measurement method according to claim 1, characterized in that: The step of determining the expected interval of the current value applied to the electrode contact combination according to the electrode identification of the electrode and the electrode contact combination currently measured comprises: determining the distance between electrode contacts in the electrode according to the electrode identifier; Determine the resistance value range between the electrode contact combination currently measured according to the distance between the electrode contacts; An expected interval of current value applied to the electrode contact combination is determined according to the measured voltage and a resistance value range between the electrode contact combination currently measured.

3. The impedance measurement method according to claim 1, characterized in that: When the current value is not within the expected current value interval, the step of adjusting the measurement voltage according to the current value comprises: If the current value is less than the lower limit of the expected current value range, increasing the measurement voltage; If the current value is greater than an upper limit of the expected current value range, the measurement voltage is reduced.

4. The impedance measurement method according to claim 3, characterized in that: If the current value is less than the lower limit of the expected current value interval, the step of increasing the measurement voltage includes: If the current value is less than the lower limit of the expected current value interval, determining the amplitude of the measured voltage increased each time according to the degree of deviation between the current value and the lower limit of the expected current value interval; and / or, If the current value is greater than the upper limit of the expected current value interval, the step of reducing the measurement voltage includes: If the current value is greater than the upper limit of the expected current value interval, the amplitude of the measured voltage to be reduced each time is determined according to the degree of deviation between the current value and the upper limit of the expected current value interval.

5. The impedance measurement method according to claim 1, characterized in that: Before the step of determining the expected interval of the current value applied to the electrode contact combination according to the electrode identification of the electrode and the electrode contact combination currently measured, the impedance measurement method further includes: The initial measurement voltage is determined according to the electrode identification.

6. The impedance measurement method according to claim 1, characterized in that: After the step of releasing the measurement voltage to the electrode contact combination and collecting the current value between the electrode contact combination, the impedance measurement method further includes: Each time the measurement voltage is adjusted, the number of measurements is accumulated; In response to the number of measurements being less than or equal to a preset number of measurements, adjusting the measurement voltage according to the current value; In response to the number of measurements being greater than the preset number of measurements, an impedance value between the electrode contact combination currently being measured is determined based on the measured voltage and the current value.

7. The impedance measurement method according to claim 6, characterized in that: Before the step of determining the expected interval of the current value applied to the electrode contact combination according to the electrode identification of the electrode and the electrode contact combination currently measured, the impedance measurement method further includes: The preset number of measurements is determined according to the electrode identifier.

8. The impedance measurement method according to claim 1, characterized in that: After the step of determining the impedance value between the electrode contact combination currently measured according to the measured voltage and the current value when the current value is within the expected current value interval, the impedance measurement method further comprises: When all electrode contact combinations on the electrode currently being measured have been measured, determining whether the measurement of other electrodes has been completed; When all electrode contact combinations on the electrode currently being measured have not been measured, the process returns to the step of determining the expected range of current values ​​applied to the electrode contact combination according to the electrode identifier of the electrode and the electrode contact combination currently being measured.

9. The impedance measurement method according to claim 8, characterized in that: When all electrode contact combinations on the electrode currently being measured have been measured, the step of determining whether the measurement of other electrodes has been completed includes: When the measurement of the other electrodes has not been completed, determining the initial measurement voltage according to the electrode identifier; When the measurement of the other electrodes is completed, the measurement is ended.

10. The impedance measurement method according to claim 1, characterized in that: The electrode identification includes at least the type of electrode contacts in the electrode and the distance between the electrode contacts.

11. An implantable medical device, characterized in that: The implantable medical device is connected to an electrode implanted at a target site of a patient, and the implantable medical device includes a processing circuit; The processing circuit comprises at least an ADC sampling module and a voltage regulating module, both of which are connected to the electrode, and the voltage regulating module is configured to at least execute the impedance measurement method according to any one of claims 1 to 10.

12. An implantable medical system, characterized in that: The implantable medical device as claimed in claim 10 further comprises electrodes, wherein the implantable medical device is connected to the electrodes and is used to measure the impedance between at least one electrode contact combination in at least one of the electrodes.

Images