Switched Diverter Circuits for MRI-Induced Lead 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, as existing technologies lack effective methods to redirect or manage the induced energy, posing risks to patients with active implantable medical devices.
Innovation Solution
A switched diverter circuit and tuned energy balanced system are employed, utilizing a diversion circuit with passive electronic components to redirect high-frequency energy induced by MRI to an energy dissipating surface, such as the housing of the active implantable medical device, thereby minimizing heating and preventing tissue damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If MRI RF pulsed field is applied for diagnostic imaging, then diagnostic capability is improved, but induced energy in implanted leads causes overheating and tissue damage
Solution Approach 1:
A diverter circuit is introduced as an intermediary component between the implanted lead and the MRI RF field. The circuit includes a capacitor coupled to the lead and an inductor coupled between the capacitor and the lead, creating a resonant circuit that diverts induced RF energy away from the distal electrode-tissue interface. This intermediary circuit protects the tissue interface from overheating while allowing the MRI procedure to proceed.
Solution Approach 2:
The diverter circuit is designed with specific electrical parameters (capacitance and inductance values) that are tuned to resonate at the MRI RF frequency. By changing the electrical parameters of the circuit components to match the MRI operating frequency, the circuit effectively diverts energy at the problematic frequency while maintaining normal lead function at other frequencies.
2Device complexity
If conventional implanted leads are used during MRI, then device simplicity is maintained, but energy redirection capability is insufficient leading to safety risks
Solution Approach 1:
The diverter circuit components (capacitor and inductor) are nested within or integrated into the existing implanted lead structure. The capacitor can be positioned at the distal end of the lead, and the inductor can be wound around or integrated with the lead wire, creating a compact assembly that adds protective functionality without significantly increasing overall device complexity or implantation 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
The solution effectively reduces temperature rises in implanted leads during MRI procedures, ensuring the safety of patients with active implantable medical devices by diverting induced energy away from sensitive tissue interfaces and dissipating it over a larger surface area, thus preventing overheating and associated hazards.
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
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 associated with the implanted lead or the leadwire, a diversion or diverter circuit associated with the energy dissipating surface, and at least one switch for diverting energy in the implanted lead or the leadwire through the diversion circuit to the energy dissipating surface. In alternate configurations, the switch may be disposed between the implanted lead or the leadwire and the diversion circuit, or disposed so that it electrically opens the implanted lead or the leadwire when diverting energy 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.