MRI Implantable Lead Coiled Inductor RF Heating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing implantable medical leads for use with pulse generators, such as neurostimulators and pacemakers, are prone to heating and induced current when exposed to the strong magnetic fields of MRI machines, which can lead to deterioration of stimulation thresholds and increased risk of cardiac tissue damage.
Innovation Solution
The development of an implantable medical lead featuring a coiled inductor with multiple filars that are electrically insulated from each other, forming a bi-filar or multi-layer configuration, which acts as an electrical pathway and provides reduced DC resistance, increased heat conduction efficiency, and large inductance at common MRI frequencies, thereby minimizing RF heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a traditional implantable medical lead is used, then the lead provides basic electrical conduction functionality, but the lead experiences RF heating and induced current when exposed to MRI magnetic fields
Solution Approach 1:
The patent changes the electrical parameters of the lead by incorporating a coiled inductor with specific inductance values (e.g., 10-100 microhenries) that are tuned to counteract RF heating at MRI frequencies. The inductor's reactive impedance is designed to be equal and opposite to the lead's capacitive reactance, canceling out harmful RF effects while maintaining DC electrical conduction for pacing functionality.
Solution Approach 2:
The lead combines multiple materials with complementary properties: electrically conductive filars (gold, platinum, or copper alloys) for electrical conduction, dielectric insulation materials (polyimide, silicone, or PTFE) for electrical isolation, and MRI-conditionally unstable materials (such as polymers that change properties under RF exposure) that provide frequency-selective filtering to block RF energy while allowing DC signals to pass.
2Ease of manufacture
If the lead structure is simplified, then the manufacturing process is easier, but the lead lacks sufficient inductance to filter RF currents effectively
Solution Approach 1:
The inductor is segmented into multiple discrete filars (typically 3-9 individual wire elements) wound in specific patterns around a central axis. Each filar contributes to the total inductance, and the segmented structure allows for flexible configuration of winding density, filar spacing, and insulation layering to achieve the desired inductance value while maintaining manufacturability through standardized coiling processes.
3Object-affected harmful factors
If the inductor is designed with high inductance to filter RF currents, then RF heating is reduced, but the lead diameter increases
Solution Approach 1:
The inductor utilizes a three-dimensional helical coiling configuration where filars are wound around a central axis in multiple layers. This vertical stacking of coil windings achieves high inductance within a compact radial profile, allowing the inductor to fit within the lead's outer sheath without significantly increasing the lead's external diameter. The multi-layer helical structure packs inductance generation into the longitudinal dimension rather than requiring increased radial thickness.
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 RF heating and maintains the integrity of the pacing circuit during MRI scans, ensuring the lead's reliability and safety for patients by filtering induced RF currents and providing redundancy and improved heat dissipation.
Implementation Method 1
The coiled inductor may form a segment of the electrical pathway and may be formed of multiple filars helically wound to form a coiled portion of the coiled inductor
Implementation Method 2
The coiled inductor... provides reduced DC resistance, increased heat conduction efficiency, and large inductance at common MRI frequencies
Implementation Method 3
filtering induced RF currents and providing redundancy and improved heat dissipation
Implementation Method 4
increased heat conduction efficiency
Data Source
AI summary
An implantable medical lead is disclosed herein. The lead may include a body and an electrical pathway. The body may include a distal portion with an electrode and a proximal portion with a lead connector end. The electrical pathway may extend between the electrode and lead connector end and may include a coiled inductor including first and second electrically conductive filar cores. The first and second filar cores may be physically joined into a unified single piece proximal terminal on a proximal end of the coiled inductor. The first and second cores may be physically joined into a unified single piece distal terminal on a distal end of the coiled inductor. The first and second filar cores may be helically wound into a coiled portion between the proximal and distal terminals, the filar cores being electrically isolated from each other in the coiled portion. The proximal terminal may be electrically coupled to a portion of the electrical pathway extending to the lead connector end, and the distal terminal may be electrically coupled to a portion of the electrical pathway extending to the electrode.