RF-Diverting Assembly for Implantable Stimulation Systems
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Solution Overview
Problem
Conventional implantable electrical stimulation systems are incompatible with magnetic resonance imaging (MRI) due to RF irradiation, which causes unwanted heating, tissue damage, and premature failure of electronic components due to induced currents.
Innovation Solution
An implantable control module with an RF-diverting assembly that includes capacitive elements and a feedthrough ground, shunting undesired RF-induced currents away from the electronic subassembly while allowing operational currents to propagate, thereby reducing damage from RF irradiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional implantable electrical stimulation systems are used, then they can provide therapeutic stimulation, but they are incompatible with MRI due to RF-induced currents causing heating and tissue damage
Solution Approach 1:
A feedthrough assembly acts as an intermediary component between the implantable stimulator and external leads. This feedthrough includes a hermetic seal with conductive pathways that are specifically designed to block RF-induced currents from entering the implantable portion during MRI procedures, while still allowing operational electrical signals to pass through for therapeutic stimulation.
Solution Approach 2:
The harmful RF-induced currents are extracted or removed from the system by using the feedthrough assembly as a barrier. The feedthrough's conductive pathways and grounding structure actively divert RF currents away from the electronic components and battery, preventing them from causing heating or damage while maintaining normal stimulator function.
2Object-affected harmful factors
If shielding structures are added to protect against RF interference, then protection against heating is improved, but device complexity increases
Solution Approach 1:
The feedthrough assembly performs multiple functions simultaneously: it provides hermetic sealing to protect internal components from body fluids, establishes electrical connections between leads and the stimulator, grounds the internal electronics, and blocks RF-induced currents during MRI. By combining these functions into a single integrated component, the design avoids adding separate shielding structures that would increase complexity.
Solution Approach 2:
The grounding structure and RF-shielding features are merged with the feedthrough housing and conductive pathways. Rather than adding separate shielding components, the feedthrough's structural elements themselves serve as the shielding and grounding mechanism, reducing the overall number of parts and simplifying the assembly process.
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 RF-diverting assembly effectively filters out RF-induced currents, preventing damage to the system electronics and ensuring safe operation during MRI procedures without interfering with the propagation of operational electrical signals.
Implementation Method 1
The RF-diverting assembly includes a plurality of capacitive elements each electrically coupled to a different one of the plurality of conductive pathways along the first major surface of the non-conductive substrate
Implementation Method 2
The RF pulses can generate transient signals in the conductors and electrodes of an implanted lead
Implementation Method 3
The feedthrough ground is also electrically coupled to each of the plurality of capacitive elements
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
An implantable control module for an electrical stimulation system includes an electronic subassembly disposed in a casing. A sealed feedthrough housing is disposed along a portion of the casing. An electrically-conductive portion of the feedthrough housing is electrically coupled to an electrically-conductive portion of the casing. Feedthrough pins extend through the feedthrough housing and couple to the electronic subassembly via conductive pathways disposed in the casing. At least a portion of the conductive pathways extend along a non- conductive substrate. An RF-diverting assembly is disposed in the casing. The RF-diverting assembly includes a feedthrough ground electrically coupled to the electrically-conductive portion of the feedthrough housing. The RF-diverting assembly also includes a plurality of capacitive elements each coupling a different one of the plurality of conductive pathways to the feedthrough ground.