Controllably Isolated Housing for MRI-Safe Implantable Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Implantable medical devices (IMDs) are susceptible to MRI-induced electromagnetic fields and RF emissions, which can cause unintended voltage and current flows, leading to interference with their operation and potential harm to patients during MRI procedures.
Innovation Solution
The implementation of a switch control mechanism that isolates the conductive housing of the IMD from its internal electronic circuits, using multiple switches and blocking diodes to prevent MRI gradient-induced and RF-induced effects, ensuring the IMD operates safely during MRI procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conductive housing of the IMD is electrically connected to internal electronic circuits, then the device can function normally for electrostimulation and sensing, but the device becomes susceptible to MRI-induced electromagnetic fields and RF emissions causing unintended voltage and current flows
Solution Approach 1:
The patent applies a dynamic isolation approach where the electrical connection between the conductive housing and internal circuits is not fixed but controllable. Switches are integrated into the circuit board to dynamically change the electrical state between connected and isolated based on operational requirements. This allows the device to transition between normal operation mode (connected) and MRI safety mode (isolated), resolving the contradiction between needing electrical connectivity for function and needing isolation for MRI safety.
Solution Approach 2:
The patent changes the electrical parameter (conductivity) of the connection between housing and circuits by using switches to alter the resistance from near-zero (connected) to near-infinity (isolated). This parameter change allows the same physical structure to serve dual purposes: providing electrical connectivity when needed for normal operation and providing electrical isolation when needed for MRI safety, thus resolving the technical contradiction.
2Reliability
If switches are used to isolate the housing from internal circuits, then MRI safety is improved, but the device complexity increases due to additional components and control mechanisms
Solution Approach 1:
The patent merges the isolation function with the existing circuit board structure by integrating switches directly into the circuit board traces and components. Rather than adding separate isolation components, the switches are combined with the existing electrical pathways, allowing the circuit board to serve both as the structural platform and as the switching mechanism carrier. This reduces overall device complexity while maintaining the isolation functionality.
Solution Approach 2:
The patent implements a self-service control mechanism where the device's own control circuitry automatically detects MRI conditions and activates the isolation switches without external intervention. The system monitors for MRI environment indicators and autonomously transitions to isolated mode, eliminating the need for complex external control systems or manual operation, thus reducing device complexity while ensuring reliable protection.
3Object-affected harmful factors
If the housing is isolated from internal circuits during MRI, then harmful electromagnetic effects are prevented, but the device cannot perform electrostimulation functions that require housing as electrode
Solution Approach 1:
The patent uses dynamic switching to enable the housing to serve different functions at different times. During normal operation, the housing is electrically connected and functions as an electrode for electrostimulation and sensing. During MRI procedures, the housing is dynamically isolated to prevent harmful electromagnetic effects. This temporal separation of functions through dynamic control resolves the contradiction between needing the housing as electrode and needing to prevent RF-induced currents.
Solution Approach 2:
The patent implements periodic transitions between connected and isolated states based on operational mode. The device alternates between normal operation (housing connected for electrostimulation) and MRI mode (housing isolated for safety). This periodic action allows the same physical structure to fulfill multiple functional requirements at different time periods, resolving the contradiction between electrostimulation capability and RF protection.
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 prevents unintended electrostimulation and RF-induced currents, maintaining the integrity and safety of IMD operations during MRI scans, thereby protecting patients and ensuring accurate device function.
Implementation Method 1
susceptible to MRI gradient induced electromagnetic field (EMF), such as along electrodes located at a distal end of the leadwires and at the IMD case housing its electronics
Data Source
AI summary
An implantable medical device or some other ambulatory medical device, such as a pacer, defibrillator, or other cardiac rhythm management device can include an electrical energy delivery circuit, such as including an integrated circuit comprising a first electrostimulation output terminal, a can terminal, and a switch control output. The ambulatory or implantable device can include at least two switches in series, each including a respective substrate electrically separate from the integrated circuit, and from each other, the switches configured to controllably isolate a conductive housing of the implantable medical device from the can terminal of the integrated circuit, such as in response to the switch control output.