Floating Current Regulator Circuit for MRI-Safe Neurostimulation
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Solution Overview
Problem
Conventional neurostimulation systems face challenges in maintaining consistent and predictable therapy delivery, particularly in the presence of electromagnetic interference (EMI) from MRI scanners, which can induce unpredictable voltage potentials and require additional programming and circuitry, leading to undesirable current flow and safety concerns.
Innovation Solution
A neurostimulation system with a current regulator (CR) circuit powered by a floating power supply, utilizing a floating ground node and charge pump to maintain a high impedance loop and actively emulate passive discharge, allowing continuous therapy delivery while mitigating EMI interference through an EMI antenna.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If conventional IPGs deliver NS therapy during MRI scans, then therapy continuity is maintained, but EMI induces unpredictable voltage potentials causing safety concerns and unpredictable current flow
Solution Approach 1:
The patent introduces a floating ground node as an intermediary between the reference ground and the CR circuit power supply. This floating ground node acts as a mediator that absorbs EMI-induced voltage fluctuations, allowing the CR circuit to maintain stable current regulation during MRI scans while keeping the IPG referenced to the stable reference ground
Solution Approach 2:
The patent segments the grounding system into two independent parts: a reference ground for the IPG and control circuits, and a floating ground node for the CR circuit power supply. This segmentation isolates the CR circuit from EMI affecting the reference ground, enabling safe therapy delivery during MRI scans
2Reliability
If stimulation therapy is turned off during MRI scans, then safety and predictability are improved, but therapy delivery is interrupted
Solution Approach 1:
The floating ground node serves as an intermediary that enables the CR circuit to operate independently from EMI-affected reference ground during MRI scans, allowing continuous safe therapy delivery without interruption
Solution Approach 2:
The patent dynamically adjusts the grounding configuration by allowing the floating ground node to float at different potentials depending on EMI conditions. During MRI scans, the floating ground node drifts to absorb EMI, while during normal operation it maintains stable connection, enabling adaptive therapy delivery
3Adaptability or versatility
If additional circuitry and programming are added to handle EMI, then EMI mitigation capability is improved, but device complexity increases
Solution Approach 1:
The floating ground node provides an elegant intermediary solution that mitigates EMI without requiring complex active compensation circuits, additional sensors, or sophisticated control algorithms. The passive floating ground configuration inherently absorbs EMI voltage fluctuations
Solution Approach 2:
The patent creates an equipotential floating ground node that maintains stable voltage potential for the CR circuit during EMI events. By keeping the CR circuit power supply terminals at stable potential difference relative to the floating ground node, the system achieves EMI mitigation through equipotentiality rather than complex active control
Data Source
AI summary
A system and method are provided that include a power supply having positive and negative terminals. The negative terminal defines a reference ground. First and second electrodes are positioned within a patient and configured to be located proximate to tissue of interest that is associated with a target region. A control circuit is configured to control delivery of current for a therapy between the first and second electrodes. A current regulator (CR) circuit is connected to, and configured to control current flow through, at least the first electrode during delivery of the therapy under direction of the control circuit. A floating power supply is connected across power supply terminals of the CR circuit. The CR circuit and floating power supply are coupled to a floating ground node that is electrically separate from the reference ground.