Variable Voltage Rail Switching for MRI-Induced Current Blocking
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Solution Overview
Problem
Implantable neurostimulation systems face challenges in preventing induced electrical currents during Magnetic Resonance Imaging (MRI) scans, which can cause unwanted stimulation and damage to the device and patient discomfort, due to the strong magnetic gradient fields inducing voltages that exceed the voltage supply rails of the Implantable Pulse Generator (IPG) electronics.
Innovation Solution
The neurostimulation device employs solid-state switching devices and a variable power source to manage voltage states, placing the switching devices in open or closed states based on the device's active or inactive state, and using a controller to output low or high voltages to prevent induced currents from external magnetic fields, such as those from MRI scanners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the IPG uses traditional voltage regulation circuitry with fixed voltage supply rails, then the device can operate reliably during normal stimulation therapy, but the fixed voltage rails cannot prevent induced currents from exceeding safe levels during MRI scans
Solution Approach 1:
The patent implements dynamic voltage rail adjustment by switching between multiple voltage supply levels (e.g., first voltage level during normal operation, second voltage level during MRI) based on detected conditions. This allows the system to adapt its electrical characteristics in real-time to prevent harmful induced currents while maintaining reliable stimulation therapy operation.
Solution Approach 2:
The system changes key electrical parameters (voltage supply levels, impedance settings) in response to detected conditions such as MRI scan detection or high induced current levels. By dynamically adjusting these parameters, the system prevents damage from excessive induced currents while maintaining normal therapeutic function during non-MRI operation.
2Object-affected harmful factors
If the neurostimulation device blocks induced currents during MRI scans, then patient safety and device protection are improved, but the device must add complexity to detect and respond to MRI conditions
Solution Approach 1:
The patent designs the IPG to perform multiple functions using existing components: the same voltage regulation circuitry that maintains stable operation during stimulation therapy also provides protection during MRI scans. The output stage components serve dual purposes of normal current delivery and induced current blocking, reducing the need for separate dedicated MRI protection hardware.
Solution Approach 2:
The system uses its own existing sensors and control circuitry to detect MRI conditions and automatically adjust its operation for protection. Rather than requiring external monitoring equipment or complex dedicated safety systems, the neurostimulator monitors its own electrical characteristics and autonomously responds to prevent damage during MRI exposure.
3Object-affected harmful factors
If the IPG uses higher voltage supply rails to accommodate induced currents during MRI, then the device can withstand MRI scanning, but the higher voltage rails may cause unwanted stimulation or tissue damage during normal therapy operation
Solution Approach 1:
The system dynamically switches between different voltage supply levels based on operational mode. During normal stimulation therapy, it operates at lower voltage levels appropriate for safe tissue stimulation. During MRI scans, it switches to higher voltage levels capable of withstanding induced currents. This dynamic adjustment ensures safety in both operational contexts without compromising therapeutic efficacy or causing unwanted stimulation.
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 solution effectively blocks induced electrical currents during MRI scans, preventing unwanted stimulation and potential damage to the IPG electronics, while allowing the device to function normally during stimulation therapy.
Implementation Method 1
strong magnetic gradient fields inducing voltages that exceed the voltage supply rails of the Implantable Pulse Generator (IPG) electronics
Data Source
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AI summary
A neurostimulation device capable of being placed between an active stimulation state and an inactive stimulation state and method of using same. The neurostimulation device comprises a plurality of electrical terminals configured for being respectively coupled to a plurality of stimulation electrodes, a first solid-state switching device coupled to a first one of the electrical terminals, a variable power source coupled to the first switching device, and a controller configured for, when the neurostimulation device is in the inactive stimulation state, prompting the variable power source to selectively output a relatively low voltage to place the first switching device into a first open state and a relatively high voltage to place the first switching device into a second open state.