Switched Lead Diverter Circuit for MRI-Induced Heating
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Solution Overview
Problem
Implanted medical leads experience excessive energy induction during MRI procedures, leading to overheating and potential tissue damage due to electromagnetic interference, which poses a significant risk to patients with active implantable medical devices such as cardiac pacemakers.
Innovation Solution
A switched diverter circuit system is implemented, comprising an energy dissipating surface and a diversion circuit with a switch that diverts high-frequency energy induced in implanted leads away from sensitive tissue interfaces to a more distant energy dissipating surface, such as the AIMD housing, using frequency-selective bandstop filters and impedance matching to minimize thermal rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MRI procedures are performed on patients with implanted leads, then diagnostic imaging can be obtained, but excessive energy is induced in the leads causing overheating and potential tissue damage
Solution Approach 1:
A diversion circuit is introduced as an intermediary element between the implanted lead and the tissue interface. This circuit provides an alternative pathway for induced electromagnetic energy to flow through a switch and dissipate away from the tissue interface, preventing excessive heating at the electrode-tissue contact point while allowing the MRI procedure to proceed.
Solution Approach 2:
The switchable diversion circuit converts the harmful induced electromagnetic energy into a beneficial protective mechanism. When activated during MRI procedures, the circuit redirects the harmful RF energy through the switch to a safe dissipation path, transforming what would be tissue-damaging energy into a controlled phenomenon that protects the tissue interface while maintaining device functionality.
2Object-affected harmful factors
If a diversion circuit is added to redirect energy, then tissue damage is prevented, but device complexity increases
Solution Approach 1:
The diversion circuit incorporates a switch that dynamically connects or disconnects the diversion path based on operational conditions. This dynamic element allows the circuit to adapt its configuration - remaining simple during normal operation while providing protective functionality when needed - thereby minimizing the increase in device complexity while maintaining the ability to prevent tissue overheating.
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
This solution effectively reduces temperature rises in implanted leads during MRI procedures, minimizing the risk of tissue damage and ensuring the continued functionality of active implantable medical devices by redirecting induced energy away from sensitive tissue interfaces.
Implementation Method 1
the radio frequency (RF) pulsed field of MRI can couple to an implanted lead in such a way that electromagnetic forces (EMFs) are induced in the lead
Implementation Method 2
when this current becomes excessive, that overheating of said lead or its associated electrode or overheating of the associated interface with body tissue can occur
Implementation Method 3
Frequency selective bandstop filters and impedance matching to minimize thermal rise
Data Source
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AI summary
An energy management system that facilitates the transfer of high frequency energy induced on an implanted lead or a leadwire includes an energy dissipating surface (161) associated with the implanted lead or the leadwire, a diversion or diverter circuit (112) associated with the energy dissipating surface (161), and at least one switch (266) disposed between the diversion circuit and the AIMD electronics (137) for diverting energy in the implanted lead or the leadwire through the diversion circuit to the energy dissipating surface. The switch may comprise a single or multi-pole double or single throw switch. The diversion circuit may be either a high pass filter or a low pass filter.