Percutaneous Lead Electrode With Optical Fiber Coupling Stability
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Solution Overview
Problem
Existing implantable pulse generators (IPGs) for spinal cord stimulation face challenges such as long-term survival in the harsh in vivo environment, device erosion due to tissue degradation, instability of optical signals for adaptive stimulation, and extended recharge times with potential temperature increases.
Innovation Solution
The improved IPG design incorporates a non-metallic case for reduced corrosion and immune response, a super ellipse curve shape to minimize erosion, stable optical signal transmission through precise lead and optical fiber coupling, and continuous charging duty cycles without eddy currents to reduce recharge time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metallic case is used in the IPG, then structural strength is improved, but corrosion and immune response occur leading to reduced device longevity
Solution Approach 1:
The patent employs a hermetic seal constructed from titanium and titanium alloys, combining the strength of metal with corrosion resistance through surface treatments and protective coatings. This composite approach maintains structural integrity while preventing degradation in the physiological environment.
Solution Approach 2:
The hermetic seal creates an inert, controlled environment inside the IPG case that isolates internal electronic components from the corrosive physiological environment. This barrier prevents moisture and tissue fluid ingress, eliminating corrosion and immune response issues while maintaining device longevity.
2Ease of manufacture
If a flat or angular IPG case shape is used, then manufacturing is simplified, but device erosion occurs due to tissue degradation at corners and edges
Solution Approach 1:
The patent specifies that the IPG case should have a substantially rounded shape with minimized sharp edges and corners. This curvature distribution prevents stress concentration and reduces tissue erosion at vulnerable points, thereby extending device longevity while maintaining manufacturability through standard molding processes.
3Ease of operation
If optical fibers are loosely coupled in the lead, then lead assembly is easier, but optical signal stability deteriorates affecting adaptive stimulation
Solution Approach 1:
The patent divides the optical coupling system into distinct functional segments: an optical interface at the IPG header, optical fibers within the lead, and connection mechanisms. This segmentation allows for standardized, pre-assembled components that maintain optical alignment while simplifying the overall assembly process through modular design.
Solution Approach 2:
The patent introduces an intermediary coupling mechanism between the IPG header optical interface and the lead optical fibers. This intermediary component ensures stable optical signal transmission while accommodating assembly variations, thereby maintaining signal stability without requiring extremely tight tolerances that would complicate manufacturing.
4Loss of energy
If the IPG is recharged with duty cycles interrupted by eddy currents, then charging efficiency is maintained, but recharge time extends and temperature increases
Solution Approach 1:
The patent employs periodic pulsed charging cycles with optimized duty ratios that allow the system to accumulate charge efficiently while preventing excessive temperature rise. The periodic interruption of charging current eliminates eddy current losses while maintaining overall charging efficiency through optimized pulse timing and duration.
Solution Approach 2:
The patent dynamically adjusts charging parameters including pulse width, frequency, and amplitude based on real-time temperature monitoring and battery state of charge. This parameter optimization enables faster recharge times by increasing power delivery when temperatures are acceptable and reducing power when thermal limits are approached, thereby eliminating the trade-off between charging efficiency and recharge time.
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 solution enhances the longevity and reliability of IPGs by preventing corrosion and erosion, maintaining stable optical signals for precise stimulation, and enabling faster and more efficient battery recharging, thus improving the effectiveness and durability of spinal cord stimulation systems.
Implementation Method 1
non-metallic case for reduced corrosion and immune response
Implementation Method 2
super ellipse curve shape to minimize erosion
Implementation Method 3
stable optical signal transmission through precise lead and optical fiber coupling
Implementation Method 4
continuous charging duty cycles without eddy currents to reduce recharge time
Data Source
AI summary
A surgical lead is provided which includes a generally flexible polymeric panel incorporating a set of electrode arrays embedded in one side. The electrode arrays are connected to integrally formed leads which house conductors that connect the electrodes to a set of contacts. The contacts engage an IPG header. The leads incorporate an optical fiber which extends from the IPG header to a set of window portals in the flexible panel. Each of the fibers includes a side firing section adjacent the optical windows for transmission or reception of light. Optimally placed reflectors and heat shields are also provided.