RF Shield for Implantable Stimulation Leads

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Solution Overview

Problem

Conventional implantable electrical stimulation systems are potentially unsafe during RF irradiation, such as MRI procedures, due to common-mode coupling of electromagnetic fields, leading to induced currents that can cause heating and disruptive voltages within electronic circuits.

Innovation Solution

Incorporation of a continuous conductive RF shield along the lead and around the control module housing, which dissipates induced currents safely, reducing the risk of tissue damage and heating by distributing the current over a larger surface area away from sensitive tissues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional implantable electrical stimulation system is used during RF irradiation (such as MRI procedures), then the system can provide therapeutic electrical stimulation, but induced currents are generated due to common-mode coupling of electromagnetic fields, causing heating and disruptive voltages that compromise safety

Engineering Contradiction:

Improvesafety during RF irradiationVSAvoidinduced currents and heating

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A continuous conductive RF shield is introduced as an intermediary component between the RF electromagnetic field and the sensitive electronic circuits/conductors in the stimulation system. The shield intercepts and dissipates induced currents through its continuous conductive path, preventing these currents from reaching and heating internal conductors and electronics, thereby eliminating the harmful heating effect while allowing the system to operate during RF irradiation

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If conductors are placed close to tissue for effective electrical stimulation, then therapeutic delivery is improved, but induced currents during RF irradiation cause localized heating and tissue damage

Engineering Contradiction:

Improvetissue safety during RF exposureVSAvoidlocalized heating and tissue damage

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The RF shield acts as a protective intermediary that intercepts induced currents before they can flow through tissue-adjacent conductors. By providing a low-impedance continuous conductive path, the shield diverts RF-induced currents away from the stimulation conductors and their adjacent tissue, preventing localized heating and tissue damage while maintaining the conductors' proximity to tissue for effective therapy delivery

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If electronic circuits are protected from induced voltages during RF irradiation, then system reliability is improved, but the complexity of the system increases due to additional shielding components

Engineering Contradiction:

Improveelectronic circuit protectionVSAvoidshielding structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The RF shield is implemented as a thin, continuous conductive layer or coating that can be applied along the lead and around electronic circuits. This thin-film approach provides effective electromagnetic shielding and induced current dissipation without adding significant bulk, weight, or structural complexity to the implantable system, making the protection mechanism minimally invasive and easy to integrate

Inventive Principle:

Principle #30Flexible shells and thin films

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 RF shield effectively reduces or eliminates the induction of currents in conductors, preventing heating and tissue damage, while ensuring safe dissipation of induced currents, thereby enhancing the safety of electrical stimulation systems during RF exposure.

Implementation Method 1

common-mode coupling of electromagnetic fields, leading to induced currents that can cause heating

Methodology Applied

Scientific EffectElectromagnetic Induction: Electromagnetic Induction

Implementation Method 2

continuous conductive RF shield... dissipates induced currents safely, reducing the risk of tissue damage and heating by distributing the current over a larger surface area

Methodology Applied

Scientific EffectConduction: Conduction (electrical)

Data Source

PatentUS10173055B2Electrical stimulation leads and systems having a RF shield along at least the lead and methods of making and using

Publication Date: 2019.01.08 BOSTON SCI NEUROMODULATION CORP

AI summary

An electrical stimulation system includes a lead or lead extension; a control module coupleable to the lead or lead extension; and a continuous conductive RF shield having a first portion extending along at least a portion of the lead and a second portion configured and arranged to form a perimeter band disposed around the housing of the control module. Alternatively, an electrical stimulation lead or lead extension includes a body; first contacts disposed along the distal end portion of the body; second contacts disposed along the proximal end portion of the body; a conductive RF shield disposed over, and extending along, at least a portion of the body; and a non-conductive jacket disposed over the conductive RF shield. The non-conductive jacket defines at least one window which exposes a portion of the conductive RF shield radially beneath the at least one window.