Electrode Switch for MRI Shielding in Implantable Devices
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Solution Overview
Problem
Implantable medical devices such as pacemakers and cardiac defibrillators experience tissue heating and unwanted voltage induction during MRI procedures due to electromagnetic radiation, which can lead to adverse effects on surrounding body tissue.
Innovation Solution
Incorporating an electrode switch in the medical device that remains open to prevent the formation of a conductive path between the lead and electrode unless a threshold voltage is exceeded, thereby shielding the electrode from electromagnetic radiation and preventing voltage induction during MRI procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lead and electrode remain continuously connected for therapy delivery, then therapeutic function is maintained, but RF induced voltages and tissue heating occur during MRI procedures
Solution Approach 1:
The electrode switch transitions between open and closed states dynamically based on the operational mode. During MRI procedures, the switch remains open to prevent RF induced voltage induction. During therapy delivery, the switch closes to enable current flow to the electrode. This dynamic state change allows the system to adapt to different operational requirements and eliminate tissue heating during MRI while maintaining therapeutic function when needed.
Solution Approach 2:
The conductive path between the lead and electrode is selectively removed by opening the electrode switch during MRI procedures. This extraction of the conductive connection prevents the lead from acting as an antenna that induces voltages from RF electromagnetic fields, thereby eliminating the harmful effect of tissue heating while allowing the electrode to remain in place for future therapeutic use.
2Ease of operation
If the electrode switch remains closed to allow therapy delivery, then current flow is enabled, but the electrode becomes susceptible to electromagnetic radiation during MRI
Solution Approach 1:
The electrode switch provides dynamic control over the conductive path, being closed during therapy delivery to enable current flow and opened during MRI procedures to block electromagnetic radiation induction. This dynamic switching capability allows the system to optimize performance for each operational mode without compromise.
3Object-affected harmful factors
If an electrode switch is added to control conductive path formation, then MRI safety is improved, but device complexity increases
Solution Approach 1:
The electrode switch acts as an intermediary component between the lead and electrode, controlling the formation of the conductive path. This single added component provides the necessary functionality to prevent voltage induction during MRI while allowing current flow during therapy, with minimal impact on overall device complexity.
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
Effectively shields the electrode and surrounding tissue from induced voltages and electromagnetic radiation, ensuring safe and effective delivery of therapeutic pulses while minimizing tissue heating during MRI scans.
Implementation Method 1
The electrode switch in the open state electrically shields the electrode from at least electromagnetic radiation within the body during an magnetic resonance imaging procedure
Implementation Method 2
a closed state allowing formation of the conductive path between the lead and the electrode upon reception of a voltage applied across the electrode switch which exceeds a threshold voltage
Data Source
AI summary
A medical device includes a pulse generator and an electrode configured to contact tissue in a body vessel. The medical device includes a lead that includes a lead connector. The lead connector connects a pulse generator with an electrode via a conductive path. An electrode switch is electrically connected between the lead conductor and the electrode. The electrode switch includes an open state preventing the conductive path between the lead and the electrode. The electrode switch includes a closed state establishing the conductive path between the lead and the electrode when a voltage is applied across the electrode switch that exceeds a threshold voltage. The electrode switch in the open state electrically shields the electrode from electromagnetic radiation and induced voltages during magnetic resonance imaging.