Implantable Electrode Stub Line for MRI Heating Reduction
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Solution Overview
Problem
Implantable electrodes used in medical devices can heat up during MRI examinations due to electromagnetic field coupling, posing a risk to patients, and existing designs struggle to prevent this heating while maintaining thin dimensions and adhering to length and resistance specifications.
Innovation Solution
The electrode incorporates a stub line connected to the electrode line to modify its effective length, shifting the resonance from series to parallel, thereby minimizing electromagnetic coupling and heating at specific MRI frequencies, using materials like silicone or polyurethane for the outer tube and flexible conductive tracks for the stub line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrode line length is increased to improve electrical performance, then the electrode can deliver signals more effectively, but the electrode becomes more susceptible to electromagnetic field coupling and heating during MRI examinations
Solution Approach 1:
The patent applies parameter changes by modifying the electrical length of the electrode line through the addition of a stub line. This changes the resonant frequency characteristics of the electrode, shifting it from series resonance (which causes heating) to parallel resonance (which minimizes heating), thereby maintaining signal delivery efficiency while reducing electromagnetic field coupling during MRI examinations
Solution Approach 2:
The stub line acts as an intermediary element that modifies the electrical characteristics of the electrode line. By introducing this additional conductive path, the patent creates a resonance condition that cancels out harmful electromagnetic field coupling while preserving the electrode's primary function of delivering electrical signals
2Shape
If the electrode is designed to be thin to meet anatomical requirements, then the electrode can be implanted in thinner tissue layers, but the electrode line length and resistance specifications become harder to maintain
Solution Approach 1:
The patent resolves the contradiction by transitioning from a single-dimensional electrode line to a two-dimensional configuration with the stub line. This allows the electrode to maintain thin overall dimensions while providing additional electrical path length through the stub line, thereby satisfying both the thin design requirement and the electrical performance specifications
3Object-affected harmful factors
If the effective line length of the electrode is optimized for series resonance to maximize electromagnetic field coupling, then the electrode heats up more significantly during MRI, but this heating should be avoided
Solution Approach 1:
The patent applies inversion by intentionally creating the opposite resonance condition. Instead of optimizing for series resonance which maximizes electromagnetic field coupling and heating, the patent designs the electrode with a stub line that creates parallel resonance. This inverted approach minimizes the harmful heating effect while still allowing necessary electromagnetic interaction
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 configuration effectively reduces electromagnetic excitation and heating during MRI, ensuring patient safety while allowing for efficient signal delivery and maintaining the electrode's thin design and performance requirements.
Implementation Method 1
The coupling of the electrode to the electromagnetic field of an MR tomograph (which generates an excitation field with an excitation frequency dependent on the magnetic field strength, for example, at approximately 64 MHz at 1.5 Tesla) is dependent here on the effective line length of the electrode lines of the electrode. If the effective line length of the electrode is in the range of a (series) resonance frequency of the electromagnetic field, electromagnetic fields may thus be coupled into the electrode and may cause the electrode to heat up
Implementation Method 2
electromagnetic fields may thus be coupled into the electrode and may cause the electrode to heat up
Implementation Method 3
The implantable electrode has an outer tube which, for example, is manufactured from an electrically insulating material, for example, a silicone or polyurethane material, and encases one or more electrode lines
Data Source
AI summary
An implantable electrode includes an outer tube, which has a distal end and a proximal end, wherein the implantable electrode is connectable in the region of the proximal end to an active device. At least one electrode line is arranged in the outer tube. At least one electrode pole, which is electrically connected to the at least one electrode line, for electrically contacting tissue surrounding the electrode in the implanted state of the electrode is arranged in the region of the distal end. A stub line for extending the electrical length of the at least one electrode line is connected to the at least one electrode line in the region of the distal end or the proximal end.