Capacitive Flex Circuit for MRI-Compatible Implantable Stimulation
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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 premature failure of electronic components, as well as tissue damage from induced currents.
Innovation Solution
An implantable control module with a sealed housing containing a pulse generator, capacitive flex circuit, and conductive pathways that include a capacitive element to modulate induced currents, preventing them from reaching the electronic subassembly during MRI procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional implantable electrical stimulation systems are used, then the system can provide therapeutic stimulation, but the system becomes incompatible with MRI due to RF pulses causing tissue damage and component failure
Solution Approach 1:
A capacitive isolation circuit is introduced as an intermediary component between the lead connector and the electronic subassembly. This circuit includes a capacitor that blocks RF induced currents from reaching the electronic components while allowing the system to function normally during MRI procedures
Solution Approach 2:
The harmful RF induced currents are extracted or blocked from the circuit path by placing a capacitor in series with the lead connection. This removes the harmful current path while preserving the therapeutic stimulation function
2Adaptability or versatility
If conventional implantable electrical stimulation systems are used, then the system can provide therapeutic stimulation, but the electronic components experience premature failure due to induced currents
Solution Approach 1:
A capacitive isolation circuit is introduced as an intermediary component between the lead connector and the electronic subassembly. This circuit includes a capacitor that blocks RF induced currents from reaching the electronic components while allowing the system to function normally during MRI procedures
Solution Approach 2:
The capacitive isolation circuit provides beforehand protection by blocking RF induced currents before they can reach and damage the electronic components. This preventive measure ensures component reliability during MRI procedures
3Adaptability or versatility
If conventional implantable electrical stimulation systems are used, then the system can provide therapeutic stimulation, but unwanted heating occurs causing tissue damage
Solution Approach 1:
The harmful RF induced currents are extracted or blocked from the circuit path by placing a capacitor in series with the lead connection. This removes the harmful current path while preserving the therapeutic stimulation function
Solution Approach 2:
A capacitive isolation circuit is introduced as an intermediary component between the lead connector and the electronic subassembly. This circuit includes a capacitor that blocks RF induced currents from reaching the electronic components while allowing the system to function normally during MRI procedures
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 the susceptibility of the electrical stimulation system to induced RF currents, preventing tissue damage and premature component failure, thereby ensuring safe operation during MRI procedures.
Implementation Method 1
R F pulses can generate transient signals in the conductors and electrodes of an implanted lead
Implementation Method 2
A capacitive flex circuit is disposed in the housing and is coupled to each of the plurality of feed through pins. For each of the plurality of feedthrough pins the capacitive flex circuit includes a first conductive path electrically coupling the feedthrough pin to a corresponding conductive pathway of the plurality of conductive pathways, and a second conductive path electrically coupling the feedthrough pin to the ground pin. The second conductive path includes a capacitive element.
Data Source
AI summary
An implantable control module for an electrical stimulation system includes an electronic subassembly disposed in a sealed conductive housing. A plurality of feedthrough pins extend through the sealed housing and couple connector contact of an external connector to the electronic subassembly. Each of the plurality of conductive pathways electrically couples a different one of the plurality of feedthrough pins to the electronic subassembly. A ground line electrically couples the electronic subassembly to the housing. A capacitive flex circuit is disposed in the housing and couples to each of the feed through pins. For each of the plurality of feedthrough pins the capacitive flex circuit includes a first conductive path electrically coupling the feedthrough pin to a corresponding conductive pathway of the plurality of conductive pathways, and a second conductive path electrically coupling the feedthrough pin to the ground pin.