MRI Compatible Leads With Multi-Layer Stacked Coil Configurations
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Solution Overview
Problem
Implantable medical leads can cause tissue damage due to heating when exposed to RF fields during MRI or other RF applications, as they couple with RF-induced electric fields, leading to unsafe temperature rises and potential device damage.
Innovation Solution
The development of RF/MRI compatible leads with multi-layer stacked coil configurations that reduce unwanted coupling to RF-induced electric fields, minimizing common mode current/voltage and heat generation, allowing safe use in MRI environments and other RF-exposed situations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional linear leads are used in MRI, then the leads can couple with RF fields and transmit signals, but tissue heating and device damage occur due to RF power deposition
Solution Approach 1:
The lead is divided into multiple conductor segments arranged in a multi-layer stacked coil configuration rather than a single continuous linear conductor. This segmentation reduces the effective electrical length of each segment, thereby reducing RF power deposition and tissue heating while maintaining signal transmission capability
Solution Approach 2:
The conductors are arranged in a three-dimensional multi-layer stacked coil configuration instead of a simple linear arrangement. This spatial reconfiguration reduces the lead's coupling with RF-induced electric fields by distributing the conductors across multiple layers and orientations, minimizing common mode current and tissue heating
2Object-affected harmful factors
If the lead structure is modified to reduce RF coupling, then tissue heating is reduced, but the lead flexibility and implantability may be compromised
Solution Approach 1:
The multi-layer stacked coil structure is constructed with flexible conductor materials and thin-film insulation layers that maintain lead flexibility despite the complex three-dimensional configuration. The segmented coil design allows the lead to bend and conform to anatomical structures while preserving the RF-shielding geometry
Solution Approach 2:
The multi-layer stacked coil configuration nests multiple conductor layers within a compact spatial envelope, with each layer positioned closely around the others. This nested arrangement maintains flexibility by concentrating the complex geometry in a small volume while preserving the RF-reducing spatial distribution
3Object-affected harmful factors
If multi-layer stacked coil configuration is used, then RF power deposition is reduced, but manufacturing complexity increases
Solution Approach 1:
The manufacturing process is divided into sequential steps for forming each conductor layer and insulation layer independently. This segmentation of the manufacturing process simplifies the creation of the complex multi-layer structure by treating each layer as a separate, manageable component that can be fabricated and assembled systematically
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 leads effectively inhibit tissue heating and prevent device damage by reducing RF power deposition, enabling safe MRI procedures and use in strong RF environments while maintaining low impedance and flexibility for chronic implantation.
Implementation Method 1
The at least one conductor has at least one segment with a multi-layer stacked coil configuration... that reduce unwanted coupling to RF-induced electric fields
Implementation Method 2
The coupling can sometimes result in local heating of tissue adjacent the lead(s) due to RF power deposition... The leads effectively inhibit tissue heating and prevent device damage by reducing RF power deposition
Data Source
AI summary
MRI/RF compatible leads include at least one conductor, a respective conductor having at least one segment with a multi-layer stacked coil configuration. The lead can be configured so that the lead heats local tissue less than about 10 degrees Celsius (typically about 5 degrees Celsius or less) or does not heat local tissue when a patient is exposed to target RF frequencies at a peak input SAR of at least about 4 W/kg and/or a whole body average SAR of at least about 2 W/kg. Related leads and methods of fabricating leads are also described.