Implantable Stimulator Localization Using RF Return-Loss Feedback
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Solution Overview
Problem
Existing implantable stimulator devices face challenges in efficiently transferring wireless power due to small antenna size and limited RF power delivery, necessitating complex and expensive medical imaging for precise location, and require innovative methods for accurate alignment and power transfer optimization.
Innovation Solution
A system utilizing non-inductive coupling and impedance monitoring to locate and optimize the alignment of an implantable wireless stimulator device, employing a controller device to compute path loss metrics and provide audio, visual, or haptic feedback for efficient power transfer without the need for medical imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If medical imaging is used to locate the implantable stimulator device, then location precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces an intermediary localization system consisting of external antennas and a controller that indirectly detects the implantable device's position through RF signal interactions. Instead of using complex medical imaging equipment, the system uses RF path loss measurements and return loss monitoring as intermediaries to determine device location and orientation, thereby reducing device complexity while maintaining location precision
Solution Approach 2:
The patent replaces the mechanical and complex medical imaging system with an electromagnetic field-based localization approach. By substituting physical imaging equipment with RF signal processing and path loss analysis, the system achieves device localization without requiring expensive and complex medical imaging infrastructure
2Power
If antenna size is increased to improve RF power delivery, then power transfer efficiency is improved, but implantable device size increases
Solution Approach 1:
The patent employs dynamic impedance modulation of the implantable antenna to optimize power transfer efficiency without increasing antenna size. By dynamically adjusting the antenna's electrical characteristics through impedance tuning circuits, the system maximizes RF power delivery from the external transmitter while maintaining a compact implantable device form factor
Solution Approach 2:
The patent changes the electrical parameters of the implantable antenna system through impedance modulation and resonant frequency tuning. By adjusting these parameters dynamically, the system optimizes power transfer efficiency without requiring physical increases in antenna dimensions, thus maintaining small device size while achieving effective power delivery
3Object-affected harmful factors
If non-inductive coupling is used to reduce heating, then harmful thermal effects are reduced, but power transfer efficiency decreases
Solution Approach 1:
The patent optimizes the electrical parameters of both external and implantable antennas to achieve efficient non-inductive (radiative) coupling. By tuning resonant frequencies and impedance matching, the system maximizes power transfer through free-space RF propagation while minimizing resistive heating losses, thereby reducing harmful thermal effects without sacrificing power transfer efficiency
Solution Approach 2:
The patent employs periodic RF signal transmission with duty cycle modulation to manage thermal effects. By transmitting RF energy in controlled periodic bursts rather than continuous waves, the system maintains effective power delivery to the implantable device while allowing thermal dissipation between pulses, thus reducing harmful heating effects while preserving overall power transfer efficiency
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 precise location and efficient power transfer to the implantable stimulator device, minimizing path loss and optimizing alignment, thereby enhancing therapeutic efficacy while reducing reliance on costly imaging techniques.
Implementation Method 1
a non-inductive antenna configured to receive an input signal from the antenna of the controller device via radiative coupling
Implementation Method 2
a circuit configured to extract electric energy from the input signal
Implementation Method 3
monitors, by modulating an impedance of a receiving non-inductive antenna on the implantable wireless stimulation device, a return loss representing electrical power reflected from the implantable wireless stimulation device to the controller device
Data Source
AI summary
Implementations provide a method that includes: placing a controller device over a surface region of the patient where the implantable wireless stimulation device has been implanted; configuring the controller device to (i) monitor a return loss representing electrical power reflected from the implantable wireless stimulation device to the controller device; (ii) compute a first path loss metric based on a first monitored return loss when the controller device is place over a first location within the surface region; (iii) compute a second path loss metric based on a second monitored return loss when the controller device is over a second location within the surface region; and (iv) generate a feedback to an operator to indicate whether the second path loss is smaller than the first path loss such that the controller device is placed at a location with more electrical energy non-inductively transferred to the implantable wireless stimulation device.