MRI Compatible Deep Brain Stimulation Lead
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Solution Overview
Problem
Implanted medical devices, such as pacemakers and deep brain stimulators, face limitations in compatibility with magnetic resonance imaging (MRI) due to radiofrequency heating effects, which can cause tissue damage and restrict access to MRI diagnostics for patients with these implants.
Innovation Solution
A novel lead design featuring a resistive tapered stripline (RTS) technology with a polymeric core and a metallic layer of varying thickness, which scatters radiofrequency waves, reducing antenna effects and heat generation during MRI scans.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive leads are used in implanted medical devices, then electrical signal transmission is achieved, but radiofrequency heating effects occur during MRI that can cause tissue damage
Solution Approach 1:
The lead wire is constructed as a composite structure with a polymeric core material surrounded by a metallic layer. The polymeric core provides electrical insulation and structural support, while the metallic layer enables electrical conductivity for signal transmission. This composite configuration allows the lead to maintain its electrical function while reducing radiofrequency energy absorption during MRI, as the polymeric core does not conduct RF waves like solid metal would.
Solution Approach 2:
The metallic layer is applied with varying thickness along the length of the lead wire, creating local variations in electrical conductivity and RF interaction properties. By adjusting the metallic layer thickness at different segments, the design optimizes electrical signal transmission in some regions while minimizing radiofrequency heating in others, particularly reducing the antenna effect at critical locations during MRI procedures.
2Adaptability or versatility
If MRI examinations are performed on patients with implanted devices, then diagnostic benefits are obtained, but access is restricted due to safety concerns about tissue heating
Solution Approach 1:
The composite construction with polymeric core and metallic layer fundamentally changes the lead's interaction with radiofrequency fields during MRI. The polymeric core material does not conduct RF waves, preventing the formation of strong induced currents that cause heating. This allows patients with implanted devices to undergo MRI examinations safely, expanding diagnostic access while maintaining tissue temperature within safe limits.
Solution Approach 2:
By changing the physical and electrical parameters of the lead wire—specifically using a polymeric core instead of solid metal and varying the metallic layer thickness—the design alters how the lead interacts with radiofrequency fields. These parameter changes reduce the lead's antenna effect and minimize energy absorption, enabling safe MRI procedures at clinically applicable field strengths.
3Reliability
If restrictive MRI conditions are imposed on implanted devices, then safety is maintained, but the number and quality of MRI scans are limited
Solution Approach 1:
The composite lead design with polymeric core and variable-thickness metallic layer inherently reduces radiofrequency heating across a broader range of MRI conditions compared to conventional solid metal leads. This allows MRI examinations to be performed with fewer restrictions on scan parameters, sequence types, and field strengths, thereby increasing both the number and quality of scans available to patients without compromising safety.
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 RTS lead design significantly decreases tissue heating and RF-induced currents, allowing a greater number of patients with medical implants to safely undergo MRI procedures without substantial heating effects, enhancing diagnostic access.
Implementation Method 1
The metallic layer includes a first section having a first thickness and a second section having a second thickness, wherein the first thickness is greater than the second thickness. The lead is substantially transparent to radio frequency waves in clinically-applicable magnetic resonance environments to avoid radio frequency heating effects.
Implementation Method 2
A major concern when performing MRI examinations in patients with electrically conductive implants is the increase in induced currents ('antenna effect') along conductive leads in the body that are exposed to the radiofrequency (RF) waves of the MRI.
Data Source
AI summary
A lead for an implanted medical device is disclosed in which the lead is adapted for electrical communication with an electrical signal source and has a distal tip with an electrode. The lead comprises a wire adapted to be placed in electrical communication with electrode. The wire includes: (i) a core comprising a polymeric material, and (ii) a metallic layer surrounding an outer surface of the core. The metallic layer includes a first section having a first thickness and a second section having a second thickness, wherein the first thickness is greater than the second thickness. The lead is substantially transparent to radio frequency waves in clinically-applicable magnetic resonance environments to reduce radio frequency absorption and avoid substantial heating effects.