Non-Uniform Resistivity Probe Wire for MRI Safety and Battery Life
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Solution Overview
Problem
Implantable medical devices, such as those used for Deep Brain Stimulation, experience heating issues during MRI scans due to induced currents, which can be detrimental to brain tissue, and traditional high resistive materials require excessive power or large batteries, compromising battery life.
Innovation Solution
A probe with a wire having non-uniform resistivity along its length, where the section closer to the electrode has higher resistivity to reduce current density and heating, while the rest of the wire has lower resistivity for improved battery life, achieved by varying material resistivity or sectional area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high resistive materials are used throughout the implantable device to reduce heating during MRI scanning, then heating effects are minimized, but much more power is required to obtain the same tissue stimulating signals, resulting in unacceptable large batteries or short battery life time
Solution Approach 1:
The wire is divided into two distinct sections with different resistivity characteristics: a first section with high resistivity (e.g., polysilicon) to minimize heating during MRI scanning, and a second section with low resistivity (e.g., metal) to reduce power consumption for signal transmission. This local differentiation allows each section to optimize for its specific function, resolving the contradiction between heating reduction and power efficiency.
Solution Approach 2:
The wire connecting the electrode to the pulse generator is segmented into two functional sections with different material properties. The first section (distal to proximal) has high resistivity for MRI safety, while the second section has low resistivity for efficient power delivery. This segmentation enables the system to simultaneously achieve both heating reduction and acceptable power consumption without requiring large batteries.
2Object-affected harmful factors
If high resistivity wire is used to reduce heating during MRI scanning, then heating and current density around the probe are minimized, but more power is required to deliver the same stimulation signal
Solution Approach 1:
Different sections of the wire are assigned different resistivity qualities based on their functional requirements. The first section near the electrode uses high resistivity material to minimize current density and heating in the sensitive brain tissue area, while the second section uses low resistivity material to efficiently conduct higher currents from the pulse generator, thereby delivering adequate stimulation power without excessive heating at the critical interface.
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 design minimizes heating and current density around the probe during MRI scans, balancing power consumption and battery life, thereby ensuring safer and more effective tissue stimulation.
Implementation Method 1
the device and surrounding tissue may be heated during scanning of the patient and device by e.g. Magnetic Resonance Imaging (MRI) scanning
Implementation Method 2
induced currents near the medical device during MRI scanning
Data Source
AI summary
The invention relates to a probe (10) for an implantable medical device. The probe has a distal end (2) and a proximal end (3), and the probe (10) moreover comprises an electrode (1) at the distal end. The electrode is connected to a wire (5) extending from the electrode to the proximal end of the probe, where the resistivity of the wire is non-uniform along the length of the wire. The wire may have high resistivity at the distal end of the probe and low resistivity wires elsewhere. The high resistivity wires reduce the peak current density in the tissue of an implanted device, and thus prevents destructive heating and/or undesired stimulation of tissue during MRI examination. This highly contributes to MR safety which is a highly desired feature for these implantable electrical stimulation devices.