MRI-Compatible Implantable Leads Using Segmented Winding Geometries

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional implantable electrical stimulation systems are incompatible with magnetic resonance imaging (MRI) due to common-mode coupling of electromagnetic fields, leading to unwanted heating and premature failure of electronic components.

Innovation Solution

The implementation of implantable electrical stimulation leads with conductors featuring winding geometries that include alternating coiled regions with different pitches and diameters, arranged into common-mode current-suppression units to reduce the susceptibility to RF irradiation during MRI.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional conductors with uniform winding geometry are used, then the lead structure is simple and easy to manufacture, but the lead is susceptible to RF irradiation during MRI causing heating and induced currents

Engineering Contradiction:

ImproveRF compatibilityVSAvoidconductor winding geometry

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The conductor is divided into multiple segments with different winding geometries along its length. Each segment has distinct pitch and/or diameter characteristics, creating a non-uniform structure that disrupts RF current flow patterns during MRI, thereby reducing heating and induced currents while maintaining manufacturability through modular construction

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the conductor are given different local properties through varying the winding pitch and diameter at specific locations. This local variation in geometry creates impedance mismatches along the conductor length that prevent uniform RF current distribution, reducing overall RF susceptibility without requiring complete redesign of the entire lead structure

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If conductors with alternating coiled regions of different pitches are implemented, then RF irradiation effects are minimized, but the manufacturing process becomes more complex

Engineering Contradiction:

ImproveRF heatingVSAvoidlead fabrication

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The conductor employs periodic variations in winding pitch and diameter along its length, creating a repeating pattern of tight and loose coiled regions. This periodic structure systematically disrupts RF current flow at regular intervals, effectively minimizing heating effects while allowing for standardized manufacturing processes that can produce the repeating patterns efficiently

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The winding parameters (pitch and diameter) are systematically changed at different locations along the conductor to optimize RF performance. By controlling these geometric parameters during manufacturing, the lead achieves reduced RF susceptibility through varied winding characteristics without requiring fundamentally new fabrication techniques

Inventive Principle:

Principle #35Parameter changes

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

The described solution effectively minimizes the effects of RF irradiation, reducing induced currents and heating, thereby enhancing the safety and reliability of the electrical stimulation systems during MRI procedures.

Implementation Method 1

designed for reducing common-mode coupling of applied electromagnetic fields

Methodology Applied

Scientific EffectElectromagnetic coupling: Electromagnetic Induction

Implementation Method 2

The RF pulses can generate transient signals in the conductors and electrodes of an implanted lead. These signals can have deleterious effects including, for example, unwanted heating of the tissue causing tissue damage

Methodology Applied

Scientific EffectRF heating: Dielectric Heating

Data Source

PatentUS9155883B2Systems and methods for making and using leads for electrical stimulation systems with improved RF compatibility

Publication Date: 2015.10.13 BOSTON SCI NEUROMODULATION CORP

AI summary

An implantable electrical stimulation lead includes electrodes and terminals disposed on opposing ends of the lead. A liner extends along a longitudinal length of the lead and has at least two different outer diameters. Conductors are coiled around the liner and electrically-couple the electrodes to the terminals. The conductors include a first conductor and a second conductor. The first conductor includes alternating first and second coiled regions. The first coiled regions have tighter pitches than the second coiled regions. The second conductor includes alternating third and fourth coiled regions. The third coiled regions have tighter pitches than the fourth coiled regions. The conductors are arranged into repeating adjacent winding geometries disposed along the longitudinal length of the lead. The repeating adjacent winding geometries each include one of the first coiled regions and one of the third coiled regions axially disposed adjacent to one another.