MRI Compatible Electrode Circuit with Resonant LC and Non-Resonant Filters
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Solution Overview
Problem
Current medical devices with elongated conductive structures, such as electrode wires, face significant challenges in MRI environments due to RF-induced heating, which existing technologies inadequately address, leading to insufficient attenuation of RF energy and potential tissue damage.
Innovation Solution
An MRI-compatible electrode circuit design featuring a combination of resonant and non-resonant filter components, including a resonant LC filter at the electrode/wire interface and distributed non-resonant filters along the wire, effectively blocks RF-induced currents and reduces heating by creating a high impedance at MRI frequencies, maintaining flexibility and maneuverability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If existing filter technologies are used in electrode wires, then some RF attenuation is achieved, but insufficient attenuation of RF energy occurs leading to tissue heating and potential damage
Solution Approach 1:
The electrode wire is divided into multiple discrete filter components distributed along its length, rather than using a single filter. This segmentation allows each filter component to attenuate RF energy locally, providing cumulative attenuation效果 that sufficiently reduces RF-induced heating throughout the wire.
Solution Approach 2:
Filter components are introduced as intermediary elements between the RF field and the electrode wire conductor. These filters act as mediators that selectively attenuate RF frequencies while allowing other signals to pass, thereby protecting the tissue from RF-induced heating without compromising the electrode's primary function.
2Length of moving object
If longer electrode wires are used to reach distant target sites, then delivery capability is improved, but RF-induced heating increases due to greater wire length
Solution Approach 1:
The long electrode wire is equipped with multiple filter components distributed along its entire length, segmenting the RF attenuation function across different locations. This ensures that regardless of the wire's length, each segment contributes to overall RF energy reduction, making the wire MRI-compatible even at extended lengths.
Solution Approach 2:
The solution moves from considering only the temporal aspect of RF attenuation to adding a spatial dimension by distributing filters along the wire's length. This dimensional approach ensures comprehensive RF attenuation coverage throughout the entire wire, addressing the heating problem that scales with wire length.
3Object-affected harmful factors
If more filter components are added to increase RF attenuation, then RF energy blocking is improved, but device complexity increases
Solution Approach 1:
Filter components are strategically placed at specific locations along the electrode wire where RF attenuation is most needed, rather than uniformly distributing them. This local quality approach optimizes RF protection while minimizing the total number of filters required, balancing attenuation effectiveness with device simplicity.
Solution Approach 2:
Rather than implementing a single complex filter that attempts to provide all attenuation in one location, the solution uses multiple simpler filter components that provide partial attenuation each. The cumulative effect of these partial actions achieves the desired overall RF attenuation while keeping individual components simple and the overall device complexity manageable.
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 proposed electrode circuit significantly attenuates RF-induced heating, preventing tissue damage and maintaining device functionality, even in longer lengths, by effectively blocking RF currents and reducing excessive heating of components, thus ensuring safer use in MRI environments.
Implementation Method 1
a resonant LC filter positioned at a distal end of the elongate body at or near an electrode/wire interface that is adapted to effectively block RF induced current from exiting the lead assembly through the electrode
Implementation Method 2
RF-induced heating, which existing technologies inadequately address, leading to insufficient attenuation of RF energy
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
An MRI compatible electrode circuit construct is provided. The construct includes at least two filter components constructed from an electrode wire. One filter component may be a single or multiple layer resonant LC filter positioned proximate an electrode that resolves the issue of insufficient attenuation by effectively blocking the RF induced current on the wire from exiting the wire through the electrode. The second filter component may include one or more non-resonant filter(s) positioned along the length of the electrode wire that resolve(s) the issue of excessive heating of the resonant LC filter by significantly attenuating the current induced on the wire before it reaches the resonant LC filter. The resonant LC filter may also be positioned distal to the end of the non-resonant filter.