Implantable Lead Safety Device for MRI RF Current Limiting

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Solution Overview

Problem

Conventional implantable electrical stimulation systems are incompatible with MRI due to RF-induced currents, which can cause tissue damage and premature failure of electronic components.

Innovation Solution

An implantable lead assembly with a current-limiting arrangement, including a safety device that couples to the lead body to limit RF-induced currents, providing an impedance of at least 50 ohms at MRI RF frequencies and preventing terminal contact with patient tissue.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional implantable electrical stimulation systems are used, then electrical stimulation therapy can be provided, but the systems are incompatible with MRI due to RF-induced currents causing tissue damage and component failure

Engineering Contradiction:

ImproveMRI compatibilityVSAvoidRF-induced currents

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

A safety device is introduced as an intermediary component between the lead and the patient's body. This safety device provides an impedance of at least 50 ohms at MRI RF frequencies, acting as a mediator that blocks RF-induced currents from reaching the patient's tissue while allowing the lead to maintain its electrical stimulation function. The safety device covers the terminals to prevent contact with patient tissue during MRI procedures.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the lead body is implanted to provide electrical stimulation, then therapeutic effect is achieved, but RF-induced currents can cause tissue overheating and damage during MRI

Engineering Contradiction:

Improvepatient safetyVSAvoidtissue overheating

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The safety device is implanted beforehand to provide preliminary protection against RF-induced heating. By providing an impedance of at least 50 ohms at MRI RF frequencies before the MRI procedure, the safety device preemptively blocks the harmful RF currents from reaching the patient's tissue, preventing overheating and tissue damage before it can occur.

Inventive Principle:

Principle #9Preliminary anti-action

3Reliability

If the safety device is coupled to the lead body to limit RF-induced currents, then patient safety is improved, but the device complexity increases

Engineering Contradiction:

Improvepatient safetyVSAvoidcurrent-limiting arrangement

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The safety device is designed as a disposable component that is implanted temporarily and then removed. This approach simplifies the overall system design by using a simple, inexpensive safety device rather than a complex permanent solution. The safety device provides necessary protection during the critical MRI procedure period and can be easily removed afterward without requiring complex retrieval mechanisms.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 solution effectively reduces the risk of tissue overheating and electronic component failure during MRI procedures, ensuring patient safety and system integrity.

Implementation Method 1

The safety device provides an impedance of at least 50 ohms at one or more MRI RF frequencies

Methodology Applied

Scientific EffectElectrical Impedance: Electrical Resistance

Implementation Method 2

The first port is configured and arranged for receiving the proximal end portion of the lead body and for covering each of the plurality of terminals to prevent the plurality of terminals from contacting patient tissue

Methodology Applied

Scientific EffectPhysical Containment: Physical Containment

Data Source

PatentUS9604066B2Systems and methods for improving RF compatibility of electrical stimulation leads

Publication Date: 2017.03.28 BOSTON SCI NEUROMODULATION CORP

AI summary

An implantable lead assembly for an electrical stimulation system includes a first lead configured for insertion into a patient. A current-limiting arrangement is coupleable with the first lead. The current-limiting arrangement is configured for limiting the amount of RF-induced current propagating along a body of the first lead during an MRI procedure. The current-liming arrangement includes a safety device configured to couple to the lead body when the lead body is implanted in the patient. The safety device defines a first port extending along a length of the safety device. The first port is configured for receiving a proximal end portion of the lead body and covering each of multiple terminals disposed along the lead body to prevent the terminals from contacting patient tissue. The safety device provides an impedance of at least 50 ohms at one or more MRI RF frequencies.