IPG Optical Folding Assembly and Heat Dissipation Pattern
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Solution Overview
Problem
Current implantable pulse generators (IPGs) for spinal cord stimulation face challenges in maintaining accurate optical feedback due to Fresnel reflections, power consumption, and heat generation, which affect the stability of the stimulation signal and battery longevity, and are hindered by lead migration and optical system degradation over time.
Innovation Solution
The IPG system incorporates an optical folding assembly with VCSELs and photodiodes, a hermetically sealed composite case with ceramic and titanium components for reduced heat dissipation, and a surface pattern for enhanced heat dissipation, along with a method to compensate for Fresnel reflections and source power variations using blue and IR light pulses to normalize the stimulation signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical feedback is used to dynamically adjust stimulation current, then stimulation accuracy is improved, but optical system degradation and Fresnel reflections cause signal instability
Solution Approach 1:
The system uses optical feedback from photodiodes to continuously monitor the optical signal strength and dynamically adjusts the stimulation current accordingly. The controller receives optical feedback signals and modifies the stimulation parameters to maintain optimal performance despite changes in optical conditions
Solution Approach 2:
The patent introduces a circulator as an intermediary component to separate the transmit and receive optical paths. This mediator device enables the system to distinguish between transmitted and received light signals, preventing interference and improving signal stability by isolating the optical feedback path from the stimulation path
2Duration of action of stationary object
If IPG operates continuously to provide chronic pain relief, then therapeutic effectiveness is improved, but power consumption reduces battery longevity
Solution Approach 1:
The system employs periodic optical feedback measurements rather than continuous monitoring, taking samples at predetermined intervals. This periodic sampling approach reduces the power consumption of the optical system while still providing sufficient feedback for maintaining effective stimulation, thereby extending battery life
Solution Approach 2:
The IPG dynamically adjusts stimulation parameters based on real-time optical feedback, allowing the system to optimize power consumption by reducing stimulation intensity when optimal pain relief is achieved, rather than maintaining constant high-level stimulation throughout the day
3Reliability
If IPG generates heat during operation, then stimulation effectiveness is maintained, but heat dissipation challenges affect device performance
Solution Approach 1:
The patent extracts the optical components (VCSELs and photodiodes) through the IPG case using a ruby window, allowing optical signals to pass through while isolating the heat-generating electrical components within the sealed case. This separation enables effective stimulation while managing heat through the optical pathway
4Measurement precision
If lead is placed precisely in epidural space for optimal stimulation, then stimulation accuracy is improved, but lead migration degrades optical feedback
Solution Approach 1:
The system performs initial calibration of optical feedback parameters during the surgical placement phase when the lead is freshly positioned. This beforehand calibration establishes baseline values that compensate for potential future lead migration, allowing the system to maintain acceptable performance despite positional changes over 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
This configuration stabilizes the optical signal, reduces power consumption and heat generation, and extends battery life while maintaining effective spinal cord stimulation by dynamically adjusting the stimulation current based on optical feedback, thus improving patient comfort and device longevity.
Implementation Method 1
a first VCSEL positioned to emit light through the optical fiber
Implementation Method 2
a second VCSEL positioned to receive reflected light from the spinal cord through the optical fiber
Implementation Method 3
compensate for Fresnel reflections and source power variations using blue and IR light pulses
Data Source
AI summary
The invention provides an IPG and lead configuration which boasts both a novel optical folding assembly and an optical processor assembly which offers the advantages of low heat generation and compact package size. The invention further provides a novel heat dissipation pattern formed in the exterior of the case. The pattern ideally takes the form of closely packed hemispherical indentions on one or more of the top and bottom IPG surfaces.