DBS Electrode Discharge Current Shaping for MRI Therapy Continuity

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Solution Overview

Problem

Deep brain stimulation (DBS) systems face challenges in maintaining therapy during Magnetic Resonance Imaging (MRI) scans and exposure to electromagnetic interference (EMI), as passive discharge methods create undesirable stimulation interference and safety concerns, particularly with monopolar DBS therapy.

Innovation Solution

An implantable pulse generator (IPG) with programmable current source and electrode selection circuitry that switches to an active discharge mode during MRI or EMI, using exponentially decreasing current to reverse electrode polarities and mimic passive discharge, maintaining a high impedance stimulation loop.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If passive discharge is used after stimulation, then battery life is prolonged and undesirable side effects are minimized, but severe therapy degradation and safety concerns occur during MRI scans and EMI events

Engineering Contradiction:

Improvetherapy safety and continuityVSAvoidstimulation interference during MRI/EMI

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the discharge mode parameter from passive to active discharge during MRI/EMI events. The controller detects MRI/EMI conditions and switches the pulse generator from passive discharge mode to active discharge mode, fundamentally changing how electrode charge is dissipated. This parameter change allows the system to maintain high impedance stimulation loops during vulnerable periods while returning to passive discharge during normal operation to conserve battery life.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system dynamically adapts its discharge behavior based on environmental conditions. The controller continuously monitors for MRI/EMI events and adjusts the discharge mode in real-time. During normal operation, passive discharge is used; during detected MRI/EMI events, active discharge is activated. This dynamic adaptation resolves the contradiction by making the discharge method conditional rather than fixed.

Inventive Principle:

Principle #15Dynamics

2Reliability

If active discharge mode is used during MRI/EMI, then therapy continuity is maintained and safety risks are minimized, but additional power is consumed from the battery

Engineering Contradiction:

Improvetherapy continuity during MRIVSAvoidbattery power consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The system takes preliminary action by detecting MRI/EMI events before they can cause therapy degradation or safety issues. The controller monitors for these conditions and proactively switches to active discharge mode in anticipation of potential problems, preventing therapy interruption before it occurs. This preliminary detection and response mechanism allows the system to maintain reliability while minimizing unnecessary power consumption by only activating active discharge when truly needed.

Inventive Principle:

Principle #9Preliminary anti-action

3Power

If monopolar DBS therapy is used with passive discharge, then efficient stimulation is achieved, but low-impedance electrical loops are created during MRI scans

Engineering Contradiction:

Improvestimulation efficiencyVSAvoidelectrical loop formation during MRI

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The system dynamically changes the impedance characteristics of the stimulation loop based on environmental conditions. During normal operation, monopolar configuration with passive discharge provides efficient stimulation. During detected MRI/EMI events, the system switches to active discharge mode which maintains high impedance, preventing the formation of dangerous low-impedance electrical loops. This dynamic impedance adjustment resolves the contradiction between stimulation efficiency and MRI safety.

Inventive Principle:

Principle #15Dynamics

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 approach allows continuous DBS therapy during MRI scans and EMI exposure, minimizing therapy degradation and safety risks while emulating the benefits of passive discharge without creating low-impedance electrical loops.

Implementation Method 1

a programmable current source configured to provide an exponentially decreasing current to the selected one or more electrodes

Methodology Applied

Scientific EffectExponential decay:

Data Source

PatentEP3946570B1Emulating passive discharge of electrodes using a programmable exponentially-decreasing amplitude discharge current

Publication Date: 2024.07.31 ADVANCED NEUROMODULATION SYSTEMS INC

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AI summary

Embodiments are directed to an implantable medical device comprising stimulation circuitry for controlling delivery of a medical therapy to a patient, a processor for controlling the IMD according to executable code, and a power source. The implantable medical device may further include current regulator circuitry comprising electrode selection circuitry that is configured to select electrodes for use during a discharge mode, and a programmable current regulator configured to provide an exponentially decreasing discharge current to the selected electrodes from the power source. A current output of a programmable current regulator may be decreased in precalculated steps to create the exponentially decreasing discharge current applied to the selected electrodes.