Implantable Medical Device Coil Mode Switching for MRI Gradient Detection
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Solution Overview
Problem
Active implanted medical devices (IMDs) face interference during magnetic resonance (MR) scans due to similar frequency content between MR-generated gradient signals and cardiac activity signals, necessitating accurate signal discrimination to maintain sensing and high-voltage therapy.
Innovation Solution
An IMD with three coils configured to operate in different modes, allowing the device to detect MR-generated gradient fields along multiple axes while also sensing biological signals and delivering therapy, using existing electronic circuitry to differentiate between MR-generated and cardiac signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic sensor is integrated into an active IMD for detection of MR generated gradient field, then sensing and high voltage therapy can be maintained during MRI scan, but numerous electronic circuitry must be added into the IMD where space is limited and manufacturing cost increases
Solution Approach 1:
The patent makes existing IMD coils multi-functional by enabling them to detect MR gradient fields in addition to their primary functions (telemetry, pacing, defibrillation). The processor switches between a first mode for primary functions and a second mode for gradient field detection, allowing one component to serve multiple purposes without adding dedicated magnetic sensors
Solution Approach 2:
The IMD uses its own existing coils and electronic circuitry to detect MR gradient fields, rather than requiring external or additional specialized components. The device serves itself by leveraging already-present hardware resources for the additional function of gradient field detection
2Measurement precision
If continuous gradient detection is enabled in the IMD, then MR generated gradient field can be accurately detected, but battery life is reduced due to continuous activation of detection circuitry
Solution Approach 1:
The processor periodically switches between the first mode (primary functions) and the second mode (gradient field detection) based on whether an MRI scan is detected. This periodic switching ensures gradient field detection occurs only when needed during MRI scans rather than continuously, thereby preserving battery life while maintaining detection accuracy when required
3Reliability
If the IMD operates in first mode for sensing biological signals, then normal cardiac monitoring is maintained, but the device cannot detect MR generated gradient field signals
Solution Approach 1:
The IMD dynamically switches between operational modes based on the detected environment. The processor monitors for MRI scan conditions and transitions from the first mode (optimized for cardiac signal sensing) to the second mode (optimized for gradient field detection) when an MRI is detected, and switches back when the MRI scan is complete. This dynamic adaptability allows the device to maintain optimal performance for different operational contexts
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 the continuation of sensing and therapy during MR scans without adding extensive electronic components, reducing manufacturing costs and preserving battery life by only activating gradient detection during scans.
Implementation Method 1
a first coil configured to operate in first and second modes. When in the second mode, the first coil is configured to detect a first time varying MR generated gradient field along a first axis
Implementation Method 2
a second coil configured to detect a second time varying MR generated gradient field along a second axis
Implementation Method 3
a third coil configured to detect a third time varying MR generated gradient field along a third axis
Data Source
AI summary
An implantable medical device (IMD) includes electronic circuitry, and one or more processors configured to switch operation of a first coil of the electronic circuitry between the first and second modes. When in the first mode, the one or more processors are configured to manage operation of the electronic circuitry and the first coil to at least one of sense biological signals, deliver treatment for a non-physiologic condition, or wirelessly communicate with at least one of an external device or second implanted device. When in the second mode, the one or more processors are configured to manage operation of the electronic circuitry and the first coil to detect the time varying MR generated gradient field along the first axis.