Modular Implantable Leads for MRI RF Suppression
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Solution Overview
Problem
Conventional implantable electrical stimulation systems are incompatible with magnetic resonance imaging (MRI) due to RF pulses causing unwanted heating and induced currents in conductors and electrodes, leading to tissue damage and premature component failure.
Innovation Solution
The development of modular implantable electrical stimulation leads with conductors arranged in low and high impedance configurations, allowing for the coupling of multiple lead elements with specific connector arrangements to mitigate RF-induced issues during MRI procedures, including coiled and twisted conductor geometries to form suppression units and manage current induction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional implantable electrical stimulation systems are used, then therapeutic efficacy is maintained, but compatibility with MRI is lost due to RF-induced heating and currents
Solution Approach 1:
The lead is divided into multiple modular lead elements (first lead element, second lead element, third lead element) that can be selectively combined. Each element can be configured with different conductor arrangements (low impedance straight/twisted or high impedance coiled), allowing the system to be segmented and reconfigured based on MRI compatibility requirements while maintaining therapeutic functionality.
Solution Approach 2:
Different portions of the lead have different impedance characteristics. The first and second lead elements use low impedance conductor arrangements for efficient stimulation, while the third lead element uses high impedance coiled conductors to suppress RF-induced currents during MRI. This local differentiation of electrical properties resolves the contradiction between therapeutic efficacy and MRI safety.
2Adaptability or versatility
If lead elements are made modular with different conductor arrangements, then MRI compatibility is improved, but device complexity increases
Solution Approach 1:
The modular lead elements are designed with universal connector interfaces that allow any element to connect to any other element. The male and female connector elements provide a standardized interface, and the insulating jacket with integrated conductor guide serves multiple functions (insulation, structural support, conductor positioning). This universality reduces the effective complexity despite having multiple configurations.
Solution Approach 2:
The conductors are nested within an insulating jacket that also contains an integrated conductor guide. The conductor guide is positioned within the insulating jacket, creating a nested structure that efficiently packs multiple functional elements into a compact form factor, reducing overall device complexity.
3Object-affected harmful factors
If coiled conductor arrangements are used in all lead elements, then RF current suppression is maximized, but electrical impedance increases and therapeutic efficacy decreases
Solution Approach 1:
The lead is segmented into functional zones: the first and second lead elements use low impedance straight or lightly twisted conductors for efficient electrical stimulation delivery, while the third lead element uses high impedance coiled conductors specifically for RF current suppression during MRI. This segmentation allows each zone to optimize for its specific function without compromising overall system performance.
Solution Approach 2:
The conductor arrangement is optimized locally for each lead element's specific function. Elements requiring efficient current delivery (first and second elements) use low impedance arrangements, while the element positioned in the MRI interference zone (third element) uses high impedance coiled conductors for RF suppression. This local optimization resolves the contradiction between RF suppression and stimulation efficacy.
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 modular lead design effectively reduces RF-induced currents and heat, enhancing safety and longevity of the stimulation system during MRI procedures while maintaining therapeutic efficacy.
Implementation Method 1
The RF pulses can generate transient signals in the conductors and electrodes of an implanted lead. These signals can have deleterious effects including, for example, unwanted heating of the tissue causing tissue damage, induced currents in the lead, or premature failure of electronic components.
Implementation Method 2
The conductors of at least one of the modular lead elements are disposed in a high impedance arrangement... the high impedance arrangement of the conductors forms at least one suppression unit
Implementation Method 3
The conductors of at least one of the modular lead elements are disposed in a low impedance arrangement
Implementation Method 4
the low impedance arrangement of the conductors includes the conductors extending along the modular lead element in either a straight configuration or a twisted configuration with twisting of the conductors at a rate of no more than one turn per centimeter
Data Source
AI summary
An implantable electrical stimulation lead includes at least three modular lead elements configured to couple together to form the lead, each of the modular lead elements including a proximal end portion, a distal end portion, and a male connector element or a female connector element disposed on at least one of the proximal end portion or the distal end portion of the modular lead element, The modular lead elements are coupleable together by insertion of a male connector element into a female connector element.