Tunable Neural Electrode With Tissue-Matched MRI Susceptibility
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Solution Overview
Problem
Implanted neural electrodes cause significant image artifacts in magnetic resonance imaging (MRI) due to mismatched magnetic susceptibilities with surrounding tissue, preventing simultaneous collection of co-located electrophysiology and fMRI data and complicating the imaging of electrode position post-implantation.
Innovation Solution
Development of MRI-compatible electrodes with a tuned magnetic susceptibility matching that of brain tissue, using a combination of paramagnetic and diamagnetic materials in specific ratios, and incorporating nanostructured materials like carbon nanotubes to reduce image artifacts and eddy currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional neural electrodes are used for neural recording and stimulation, then neural signal measurement and stimulation functions are achieved, but significant image artifacts are produced in MRI that prevent co-located fMRI data collection
Solution Approach 1:
The electrode incorporates a composite material structure with a core made of MR-compatible material (such as titanium or stainless steel) and an outer coating of electrically conductive polymer (such as PEDOT). This composite structure allows the electrode to maintain electrical functionality while reducing magnetic susceptibility artifacts in MRI imaging, enabling both neural recording and fMRI data collection.
Solution Approach 2:
The invention changes the magnetic susceptibility parameter of the electrode material to match that of surrounding brain tissue. By using MR-compatible materials with tuned magnetic properties, the electrode's magnetic susceptibility is adjusted to minimize field distortions and image artifacts during MRI scanning, allowing simultaneous electrophysiology and fMRI measurements.
2Power
If electrodes with high electrical conductivity are used for effective neural stimulation, then stimulation efficacy is improved, but eddy currents are induced during MRI that cause tissue heating
Solution Approach 1:
The electrode's electrical conductivity parameter is optimized by using conductive polymer coatings with controlled thickness and composition. This allows the electrode to provide sufficient stimulation power while reducing eddy current induction during MRI, thereby minimizing tissue heating risks.
Solution Approach 2:
The conductive polymer coating provides continuous electrical conductivity along the electrode surface, enabling effective neural stimulation while the material's inherent properties reduce eddy current formation during MRI scanning, maintaining both stimulation efficacy and safety.
3Strength
If metallic electrodes are used for durable implantation, then mechanical strength and durability are improved, but magnetic susceptibility mismatch with tissue causes image artifacts and immune response
Solution Approach 1:
The electrode uses a composite structure where a strong metallic core provides mechanical durability and structural integrity, while an outer biocompatible polymer coating reduces magnetic susceptibility mismatch and minimizes immune response. This combination allows the electrode to maintain strength while being more compatible with surrounding tissue.
Solution Approach 2:
Different parts of the electrode have different material properties optimized for their specific functions: the core provides mechanical strength, while the surface coating provides magnetic compatibility and biocompatibility. This local differentiation allows the electrode to simultaneously achieve durability and reduced immune response.
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
Enables simultaneous fMRI and neural signal acquisition with reduced image artifacts, allowing precise imaging of implanted electrodes and improved understanding of neural stimulation mechanisms, such as DBS, by minimizing tissue heating and immune response.
Implementation Method 1
at least one electrode or signal line includes a diamagnetic material and paramagnetic material in a tuned and particular ratio selected based on a physiological tissue susceptibility property
Implementation Method 2
the tuned ratio is selected based on a magnetic susceptibility of the electrode or of the signal line
Implementation Method 3
incorporating nanostructured materials like carbon nanotubes to reduce image artifacts and eddy currents
Data Source
AI summary
A device includes a substrate, an electrode, an electrical pad, and a signal line. The signal line is coupled to the substrate and covered by an insulation layer. The signal line is coupled to the electrical pad and the electrode. At least one of the electrode and the signal line includes a diamagnetic material and paramagnetic material, wherein a ratio of the diamagnetic material and the paramagnetic material is selected based on the susceptibility properties of a physiological tissue. The term paramagnetic herein refers to magnetic susceptibility greater than that of the surrounding tissue and diamagnetic refers to magnetic susceptibility lower than that of the tissue.