MRI Lead Coils Reduce Tissue Heating
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Solution Overview
Problem
MRI-guided systems face challenges with localized tissue heating due to induced RF currents from coaxial cables and elongated devices in MRI environments, causing image artifacts and potential tissue damage.
Innovation Solution
The use of elongate electrical lead subassemblies with alternating single layer and multi-layer coil sections, where each multi-layer coil section is coiled around a single layer coil section, and vice versa, to maintain a constant diameter and achieve impedance greater than 50 ohms per centimeter at MRI frequencies, reducing RF coupling and tissue heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coaxial cables and elongated devices are used in MRI environments, then electrical connectivity and device functionality are maintained, but induced RF currents cause localized tissue heating and image artifacts
Solution Approach 1:
The electrical lead is divided into multiple discrete coil sections (first coil section, second coil section, third coil section) rather than using a continuous coaxial cable. Each coil section is independently configured with specific impedance characteristics, allowing the system to maintain electrical connectivity while reducing RF coupling and tissue heating through segmented impedance management.
Solution Approach 2:
The patent changes the electrical parameters of the lead by configuring coil sections with specific impedance values (e.g., 50 ohms, 75 ohms, or higher) at MRI frequencies. This parameter modification reduces RF current induction and associated tissue heating while maintaining necessary electrical connectivity for device functionality.
2Reliability
If conventional coaxial cables are used, then electrical connectivity is maintained, but significant image artifacts are produced
Solution Approach 1:
The continuous coaxial cable is segmented into discrete coil sections with specific impedance characteristics. This segmentation reduces RF coupling and the resulting image artifacts while preserving electrical connectivity for signal transmission, thereby maintaining both electrical functionality and image quality.
Solution Approach 2:
The impedance parameters of the electrical lead are modified through the coil section configuration to reduce RF current induction. This parameter change minimizes image artifacts caused by RF coupling while maintaining adequate electrical connectivity for device operation.
3Object-affected harmful factors
If impedance greater than 50 ohms per centimeter is achieved through multi-layer coil sections, then RF coupling is reduced, but device complexity increases
Solution Approach 1:
The lead structure is segmented into alternating single-layer and multi-layer coil sections. This segmentation achieves the desired high impedance (>50 ohms/cm) for RF coupling reduction while distributing the complexity across manageable discrete sections rather than requiring a uniformly complex structure throughout.
Solution Approach 2:
Multi-layer coil sections are strategically positioned at specific locations along the electrical lead where high impedance is most beneficial for reducing RF coupling. Single-layer sections are used in other regions, creating local variations in structure that optimize RF performance while minimizing 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
This configuration effectively minimizes localized tissue heating and image artifacts, ensuring safer and more accurate MRI-guided procedures by reducing RF energy deposition in tissues.
Implementation Method 1
Induced RF currents (referred to as RF coupling) on coaxial cables, electrical leads, guide wires, and other elongated devices utilized in MRI environments can be problematic
Implementation Method 2
induce undesired RF energy deposition in the tissue in contact/adjacent with the device, resulting in local tissue heating and permanent tissue damage
Data Source
AI summary
An elongate electrical lead assembly that reduces localized heating due to MR scanner-induced currents includes a first elongate electrical lead having a series of alternating single layer coil sections and multi-layer coil sections, a second elongate electrical lead having a series of alternating single layer coil sections and multi-layer coil sections, and a third elongate electrical lead having a coiled section that coaxially surrounds the first and second electrical leads. Each multi-layer coil section of the second electrical lead is coiled around a respective single layer coil section of the first electrical lead, and each single layer coil section of the second electrical lead is coiled around a respective multi-layer coil section of the first electrical lead.