Electric Field Imaging Feedback for Closed-Loop Stimulation Control

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Solution Overview

Problem

Existing medical devices face challenges in providing closed-loop control of electrical stimulation therapy due to the unpredictability of evoked compound action potentials (ECAPs), especially in patients where sub-perception threshold stimulation is required, as ECAPs may not be detectable, leading to ineffective feedback for adjusting stimulation parameters.

Innovation Solution

The use of electric field imaging as an informative feedback signal, in combination with other signals like ECAPs, to monitor and adjust electrical stimulation therapy, allowing for closed-loop control and sub-perception threshold stimulation without relying on detectable ECAPs, by sensing the electrical stimulation delivered to tissue and tracking changes in the electric field to adjust stimulation parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ECAP-based feedback control is used, then closed-loop control of stimulation therapy is achieved, but the system fails when ECAPs are not detectable (sub-perception threshold stimulation)

Engineering Contradiction:

Improvefeedback control reliabilityVSAvoidapplicability to sub-perception stimulation

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent introduces electric field imaging as an intermediary measurement method. Instead of directly measuring ECAPs (which fail at sub-perception thresholds), the system measures the electric field generated by stimulation pulses as an intermediate quantity that correlates with ECAP amplitude. This intermediary measurement enables feedback control to function across the full range of stimulation amplitudes, including sub-perception thresholds where traditional ECAP measurement fails.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If stimulation amplitude is reduced to sub-perception threshold, then patient comfort is improved, but ECAP detectability is lost

Engineering Contradiction:

Improvepatient discomfortVSAvoidECAP detectability

Core Design Contradiction:

Object-affected harmful factorsVSMeasurement precision

Solution Approach 1:

The patent implements a feedback control system that uses electric field imaging measurements to automatically adjust stimulation amplitude. The system measures the electric field, compares it to a target value, and adjusts the stimulation amplitude accordingly. This closed-loop feedback enables the system to maintain optimal sub-perception threshold stimulation levels, providing patient comfort while ensuring sufficient neural activation for therapeutic effect.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the measurement parameter from ECAP amplitude (which becomes undetectable at low stimulation levels) to electric field amplitude (which remains measurable across all stimulation levels). This parameter substitution allows the system to maintain measurement capability while operating at comfortable, sub-perception stimulation amplitudes.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If electric field imaging is used for feedback, then closed-loop control is achieved across all stimulation amplitudes, but additional sensing and processing requirements are introduced

Engineering Contradiction:

Improvefeedback control across stimulation rangesVSAvoidsensing and processing circuitry

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent makes the sensing circuitry universal by enabling it to perform both traditional ECAP measurement and electric field imaging measurement using the same hardware infrastructure. The sensing electrodes and signal processing circuitry are designed to accommodate multiple measurement modalities, reducing the need for separate dedicated components and minimizing the increase in device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Enables effective closed-loop control of electrical stimulation therapy, improving patient comfort and treatment efficacy by allowing adjustments based on electric field imaging, even in cases where ECAPs are not detectable, and providing robust feedback across a range of stimulation amplitudes.

Implementation Method 1

sensing circuitry configured to sense the delivered electrical stimulation

Methodology Applied

Scientific EffectElectric field sensing: Electric Field

Data Source

PatentUS20240100342A1Feedback control of electrical stimulation therapy based on electric field imaging

Publication Date: 2024.03.28 MEDTRONIC INC

AI summary

Devices, systems, and techniques are described that use electric field imaging (often referred to as the sensed stimulation artifact representative of a delivered stimulus) as an informative feedback signal to provide closed loop control of electrical stimulation therapy. In some examples, the electric field imaging may be used in combination with other feedback signals, such as ECAP do monitor and adjust the delivered electrical stimulation therapy.