ECAP Propagation Modeling for Faster Neurostimulation Response Detection
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Solution Overview
Problem
Existing neuromodulation systems face challenges in accurately measuring neural responses due to the difficulty in distinguishing evoked compound action potentials (ECAPs) from stimulus crosstalk and electrode artefacts, which are impractical to resolve with current amplifier dynamic ranges, and require efficient parameter setting for optimal ECAP detection to maintain therapeutic stimulus intensity and reduce energy consumption.
Innovation Solution
A method for selecting optimal parameter combinations for a parametric ECAP detector using differential measurements at known electrode pairs, employing a single-ended ECAP model and propagation model to estimate arrival time and morphology, reducing the need for exhaustive searches and improving measurement efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional measurement methods are used to detect ECAPs, then neural response measurement is attempted, but the ECAP signal cannot be distinguished from stimulus crosstalk and electrode artefacts due to insufficient amplifier dynamic range
Solution Approach 1:
The patent segments the ECAP detection process into two distinct phases: (1) a test phase where test stimuli are applied and ECAPs are measured at multiple electrode pairs to build a propagation model, and (2) a measurement phase where the model is used to predict and subtract artefacts from actual ECAP measurements. This segmentation allows the system to characterize the artefact ECAP relationship separately from the actual neural response measurement, resolving the dynamic range problem.
Solution Approach 2:
The patent performs preliminary characterization of the electrode pair geometry and ECAP propagation properties before actual ECAP measurement. By applying test stimuli and measuring ECAPs at multiple electrode pairs in advance, the system builds a propagation model that predicts artefact characteristics. This preliminary action enables the system to compensate for artefacts during actual measurement without requiring excessive amplifier dynamic range.
2Measurement precision
If exhaustive search is used to find optimal ECAP detector parameters at each electrode pair, then measurement accuracy is improved, but the time required to evaluate multiple electrode pairs increases significantly
Solution Approach 1:
The patent creates a universal ECAP propagation model that captures the essential characteristics of ECAP propagation across multiple electrode pairs. Instead of performing exhaustive searches at each electrode pair independently, the system builds a single propagation model during the test phase that can be applied universally to predict ECAP characteristics at any electrode pair during the measurement phase, dramatically reducing computation time.
Solution Approach 2:
The patent uses the ECAP propagation model to create a copy or prediction of what the ECAP signal would look like at different electrode pairs based on measurements from a reference electrode pair. This copying approach allows the system to estimate optimal parameters for multiple electrode pairs without performing exhaustive searches at each location, significantly reducing the time required while maintaining measurement accuracy.
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 approach significantly reduces the time required to evaluate ECAP measurements at multiple electrode pairs, enabling more precise neural response detection and efficient energy use by optimizing stimulus parameters for therapeutic efficacy.
Implementation Method 1
an electrical pulse of sufficient intensity applied to the target neural fibres by a stimulus electrode causes the depolarisation of neurons in the fibres, which in turn generates an action potential in the fibres
Implementation Method 2
measurement circuitry configured to process signals sensed at each pair of sense electrodes subsequent to the delivered neural stimulus, each sensed signal including a differential evoked compound action potential (ECAP)
Data Source
AI summary
Disclosed is a neurostimulation system comprising an implantable device for controllably delivering a neural stimulus, and a processor. Signals evoked by a stimulus are sensed at each pair of sense electrodes, each sensed signal including a differential evoked compound action potential (ECAP) evoked by the delivered neural stimulus. The differential ECAP is decomposed in each sensed signal into a first single-ended ECAP corresponding to one sense electrode of the pair of sense electrodes and a second single-ended ECAP corresponding to the other sense electrode of the pair of sense electrodes. ECAP propagation model parameters are determined from the first single-ended ECAP model and the second single-ended ECAP model and from distances of the respective sense electrodes from the stimulus electrode configuration. An indication may be given to a user if one of the one or more ECAP propagation model parameters departs from a predetermined range. Or, originating ECAP model parameters may be determined from the first single-ended ECAP model and from the distance of the corresponding sense electrode from the stimulus electrode configuration. Parameters of a model of a differential ECAP at a second pair of sense electrodes may be computed; and an optimal combination of parameters for a parametric ECAP detector at the second pair of sense electrodes may be computed from the parameters of the model of the differential ECAP.