Finite Element Model Capacitance for Neural Stimulation

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Solution Overview

Problem

Current deep brain stimulation (DBS) and other neuromodulation techniques face challenges in accurately predicting the volume of activation (VOA) due to oversimplification of electrode and tissue capacitance, leading to significant errors in therapeutic effectiveness and side effects.

Innovation Solution

Development of a finite element model (FEM) that integrates capacitive components of the electrode-tissue interface, using a Fourier FEM solver to calculate the potential distribution in tissue and couple it with multi-compartment neuron models to predict neural activation volumes as a function of stimulation parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If electrostatic approximation is used to model neural stimulation, then the model is simpler and easier to compute, but the volume of activation is overestimated by approximately 30%

Engineering Contradiction:
Improvemodel complexityVSAvoidvolume of activation prediction accuracy
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The patent changes the fundamental parameters of the model by incorporating time-dependent capacitance effects and using realistic stimulus waveforms (asymmetric biphasic pulses) instead of static electrostatic assumptions. This transforms the model from a simplified DC-based approach to a dynamic AC-based approach that accounts for electrode and tissue capacitance, thereby improving prediction accuracy without excessive complexity increase

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent replaces the electrostatic mechanical analogy with an electrical circuit model that explicitly includes capacitance elements. By substituting the purely conductive tissue model with a capacitive-resistive model that mirrors actual electrode-tissue interface physics, the model achieves better accuracy in predicting activation volumes while maintaining computational tractability through established electrical modeling techniques

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If voltage-controlled stimulation with asymmetric biphasic waveforms is used, then therapeutic effectiveness is improved, but electrostatic models overestimate the volume of activation

Engineering Contradiction:
Improvetherapeutic effectivenessVSAvoidvolume of activation prediction accuracy
Core Design Contradiction:
ReliabilityVSMeasurement precision

Solution Approach 1:

The patent introduces dynamic elements by modeling the time-varying behavior of voltage-controlled stimulators with asymmetric biphasic waveforms. The model captures the transient capacitive charging and discharging phases, as well as the asymmetric nature of clinical waveforms, allowing accurate prediction of how these dynamic stimulation patterns actually activate neural tissue compared to static electrostatic assumptions

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent incorporates periodic stimulation patterns with specific pulse widths and inter-pulse intervals that match clinical protocols. By modeling the periodic asymmetric biphasic waveforms with their characteristic cathodic and anodic phases, the model accurately predicts neural activation during realistic therapeutic stimulation cycles rather than continuous static fields

Inventive Principle:
Principle #19Periodic action

3Productivity

If electrode capacitance and tissue capacitance are ignored, then calculations are simpler, but the volume of activation is significantly overestimated

Engineering Contradiction:
Improvecalculation efficiencyVSAvoidvolume of activation prediction accuracy
Core Design Contradiction:
ProductivityVSMeasurement precision

Solution Approach 1:

The patent introduces capacitance elements as intermediary components between the voltage source and the tissue. By placing capacitive elements at the electrode-tissue interface and within the tissue model, the system accurately mediates the relationship between applied voltage and resulting current distribution, preventing direct overestimation of activation volumes while maintaining computational efficiency through standard circuit analysis methods

Inventive Principle:
Principle #24Intermediary (Mediator)

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 provides more accurate predictions of VOA, reducing errors by up to 30% compared to electrostatic models, and allows for optimized electrode design to enhance therapeutic effectiveness and minimize side effects in DBS and other neuromodulation procedures.

Implementation Method 1

A Fourier FEM solver determines the potential distribution in the tissue medium in time and space concurrently... electric field data from the determined potential distribution can be coupled to a multi-compartment neuron model to predict neural activation

Methodology Applied
Scientific EffectCapacitance: Capacitance

Implementation Method 2

A Fourier FEM solver determines the potential distribution in the tissue medium in time and space concurrently... by separating a stimulus waveform into frequency components, obtaining a solution of the Poisson equation at least one frequency component

Methodology Applied
Scientific EffectPoisson equation:

Data Source

PatentUS8606360B2Systems and methods for determining volume of activation for spinal cord and peripheral nerve stimulation
Publication Date: 2013.12.10 THE CLEVELAND CLINIC FOUND
  • US8606360B2 patent drawing
  • US8606360B2 patent drawing
  • US8606360B2 patent drawing

AI summary

This document discloses, among other things, systems and methods for determining volume of activation for spinal cord stimulation (“SCS”) using a finite element model (FEM) circuit to determine a FEM of an implanted electrode and a spinal cord in which the electrode is implanted, a Fourier FEM solver circuit to calculate a potential distribution in the spinal cord using information from the FEM circuit and a capacitive component of at least one of the implanted electrode and the spinal cord, and a volume of activation (VOA) circuit to predict a VOA using the potential distribution and a neuron model.