Electrode Impedance Selection for Clearer ECAP Sensing
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Solution Overview
Problem
Existing medical devices face challenges in accurately determining electrode positioning for sensing evoked compound action potential (ECAP) signals due to the diffused nature of these signals and the difficulty in identifying whether electrodes are under bones, which have higher impedance and can better confine the signal, using conventional imaging techniques.
Innovation Solution
Utilizing electrical impedance measurements to determine which electrodes are under bones, such as the laminar bone, by identifying higher impedance values, which are indicative of better positioning for ECAP signal sensing and stimulation, thereby enhancing signal amplitude and directionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If imaging techniques are used to determine electrode positioning, then electrode placement can be visualized, but the process becomes more intrusive and complex post-operatively
Solution Approach 1:
The patent replaces imaging techniques (mechanical/optical system) with electrical impedance measurements (electrical system) to determine electrode positioning. The medical device measures impedance values through electrodes to infer whether they are positioned under bone, substituting complex imaging with simpler electrical measurements.
Solution Approach 2:
The patent uses electrical impedance as an intermediary parameter to indirectly determine electrode positioning. Instead of directly visualizing electrode location through imaging, the system measures impedance (which varies based on tissue type) to infer positioning, using impedance as a mediator between the electrode and its spatial location.
2Measurement precision
If electrodes are positioned under the laminar bone, then ECAP signal sensing is improved with higher amplitude and reduced noise, but electrode impedance increases
Solution Approach 1:
The patent uses measured electrode impedance values as feedback to determine optimal electrode selection for ECAP sensing. The system measures impedance, compares it against thresholds or reference values, and uses this feedback to identify whether electrodes are under bone, thereby selecting the best electrodes for signal sensing despite the impedance trade-off.
Solution Approach 2:
The patent changes the selection criterion from minimizing impedance to selecting electrodes with higher impedance values that are characteristic of bone-contacting electrodes. By changing the parameter threshold for electrode selection, the system prioritizes ECAP signal quality over low impedance, accepting higher impedance as a trade-off for better signal detection.
3Reliability
If higher stimulation amplitudes are used to overcome noise, then ECAP signals can be detected more reliably, but energy consumption increases
Solution Approach 1:
The patent performs preliminary impedance measurements to identify and select optimal electrodes for ECAP sensing before delivering stimulation. By pre-selecting electrodes that are positioned under bone (which provide better signal confinement and higher amplitude), the system ensures reliable ECAP detection at lower stimulation amplitudes, reducing energy consumption before the actual stimulation occurs.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for more accurate electrode selection, improving the ability to differentiate ECAP signals from noise, reducing energy consumption, and minimizing stimulation artifacts by ensuring electrodes are positioned to maximize signal confinement and directionality towards the target neural tissue.
Implementation Method 1
A bone, such as a laminar bone, tends to have higher electrical impedance compared to nearby tissue. Accordingly, the bone tends to restrict the emanation of the ECAP signal and confines the ECAP signal.
Implementation Method 2
This disclosure describes example techniques to determine impedance of electrodes from which electrodes that are likely to be under the bone can be selected for sensing ECAP signals.
Data Source
AI summary
An example medical device includes processing circuitry configured to determine an electrode impedance value for each of one or more electrodes of a lead coupled to the medical device, identify one or more of the electrodes having electrode impedance values that are greater than electrode impedance values of other electrodes of the lead, from the identified one or more electrodes, determine a recommendation of electrodes to use for sensing a signal, and output information indicative of the recommendation.