Decoy Conductor Lead for MRI Heating Reduction
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Solution Overview
Problem
Active implantable medical device leads, particularly those used in neuro-stimulators, face issues during magnetic resonance imaging (MRI) due to heating and potential tissue damage caused by electromagnetic currents, leading to unintended stimulation and risk of implant damage.
Innovation Solution
An electrode assembly with an elongated biocompatible, electrically non-conductive body containing electrically conductive filaments and at least one elongated decoy conductor with higher electrical resistance, which electromagnetically couples with the conductive filaments to dissipate energy from induced radiofrequency currents, reducing heat generation and tissue damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conductors are coiled in a multi-layer structure to reduce MRI heating, then heat generation is reduced, but inductance increases
Solution Approach 1:
The lead body is segmented into multiple independent lumens, each containing a straight conductor. This segmentation prevents the formation of continuous current loops that would generate high inductance, while still allowing distributed heat dissipation throughout the lead structure during MRI exposure.
Solution Approach 2:
Electrically insulating material is introduced as an intermediary between adjacent conductors in the multi-lumen structure. This intermediary prevents electromagnetic coupling and inductance generation between conductors while maintaining the spatial distribution needed for heat management during MRI procedures.
2Reliability
If straight conductors are used in the lead body, then inductance is reduced, but heat dissipation capability during MRI is insufficient
Solution Approach 1:
The solution moves from a single-dimension approach (coiling conductors) to a multi-dimensional approach by arranging multiple straight conductors in parallel lumens. This spatial distribution across multiple dimensions allows heat to dissipate along the length of each conductor while the parallel arrangement prevents inductance accumulation.
Solution Approach 2:
Each lumen contains a straight conductor with locally optimized properties for minimizing inductance, while the collective arrangement of multiple lumens provides distributed heat dissipation capability. The local quality of each conductor is optimized for electrical performance, while the global arrangement addresses thermal management.
3Reliability
If conductor diameter is increased to reduce resistance, then electrical conductivity improves, but lead stiffness increases
Solution Approach 1:
The electrical conduction function is segmented across multiple thin conductors in parallel lumens rather than using a single thick conductor. This segmentation maintains low overall resistance through parallel conduction paths while keeping each individual conductor flexible, thereby maintaining lead flexibility.
Solution Approach 2:
The lead employs a composite structure combining multiple thin conductive elements with electrically insulating material. This composite construction achieves the electrical conductivity of thicker conductors through parallel paths while the insulating material and distributed structure maintain flexibility and reduce stiffness.
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 minimizes heat generation and tissue damage during MRI by dissipating induced currents through the decoy conductor, ensuring safer operation of implantable medical devices during magnetic resonance imaging.
Implementation Method 1
at least one elongated decoy conductor inside the elongated body to electromagnetically couple with the plurality of electrically conductive filaments
Implementation Method 2
the at least one decoy conductor has a higher electrical resistance than the plurality of electrical conductive filaments to dissipate energy from currents induced by radio frequencies
Data Source
AI summary
A lead (1) for an active implantable medical device comprising: an elongated, biocompatible, electrically non-conductive body (3); a plurality of electrically conductive filaments (5) inside the elongated body (3) to electrically connect electrical connectors (6) to corresponding electrodes (8); and at least one elongated decoy conductor (10) inside the elongated body (3) to electromagnetically couple with the plurality of electrically conductive filaments (5), wherein the at least one decoy conductor (10) has a higher electrical resistance than the plurality of electrical conductive filaments (5) to dissipate energy from currents induced by radio frequencies.