Inductive Switching Power Supply MRI Mode Detection
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Solution Overview
Problem
Implantable medical devices (IMDs) face challenges during MRI procedures due to the risks of intense magnetic fields, which can cause unwanted torques, forces, or heating, and disrupt their operation, requiring manual reconfiguration by skilled professionals, and existing power supplies are affected by external electromagnetic fields.
Innovation Solution
An IMD with an inductive switching power supply that can automatically detect intense magnetic fields and switch to an MRI mode by adjusting operating parameters, such as using a saturated core and modifying charge and dump phases, and includes a magnetic field detector and controller circuit to manage power supply operations safely during MRI procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an inductive switching power supply is used in an IMD, then power supply efficiency is improved, but the device becomes vulnerable to disruption by external electromagnetic fields during MRI procedures
Solution Approach 1:
The power supply operates in two dynamic modes: normal mode for efficient operation during everyday use, and MRI mode for safe operation during magnetic resonance imaging procedures. The system dynamically switches between modes based on detection of the magnetic field environment, allowing it to maintain high efficiency when needed while ensuring reliability during MRI procedures.
Solution Approach 2:
The patent changes key operating parameters when transitioning to MRI mode: the inductor core is driven into saturation to reduce inductance value, switching frequency is adjusted, and charge/dump phase durations are modified. These parameter changes make the power supply resilient to external electromagnetic fields during MRI while maintaining acceptable efficiency.
2Ease of operation
If the IMD automatically detects magnetic fields and switches to MRI mode, then the burden on medical professionals is reduced, but the device complexity increases
Solution Approach 1:
The IMD performs self-service by automatically detecting the presence of a magnetic field during MRI procedures and autonomously switching to the appropriate MRI mode. This eliminates the need for manual reconfiguration by medical professionals, significantly easing the operation burden while the added complexity is confined to the automatic detection and switching mechanism.
Solution Approach 2:
The system incorporates feedback through magnetic field detection circuitry that continuously monitors the operating environment. When the detector senses the characteristic magnetic field signature of an MRI scanner, it provides feedback to the control logic, which then automatically transitions the power supply to MRI mode, creating a closed-loop system that simplifies operation.
3Reliability
If the inductor uses a saturated core during MRI mode, then the power supply becomes resistant to external magnetic fields, but the inductance value decreases affecting power conversion
Solution Approach 1:
The patent compensates for the decreased inductance caused by core saturation by adjusting other operating parameters: increasing the switching frequency and modifying the charge and dump phase durations. These parameter changes work together to maintain adequate power conversion capability even when the inductor operates with reduced inductance during MRI mode.
Solution Approach 2:
The system dynamically adjusts multiple parameters simultaneously when entering MRI mode: the inductor core saturation state, switching frequency, charge phase duration, and dump phase duration are all modified in coordination. This dynamic multi-parameter adjustment allows the power supply to maintain functional performance despite the reduced inductance, balancing field resistance with power conversion capability.
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
The solution enables the IMD to automatically configure itself for safe operation during MRI scans, reducing the burden on medical professionals and ensuring continuous therapy delivery while minimizing risks to the device and patient, and effectively manages power supply efficiency in intense magnetic fields.
Implementation Method 1
an inductive switching supply including an inductor having a ferromagnetic core
Implementation Method 2
A magnetic field detector can be included to detect an intense magnetic field
Implementation Method 3
In the MRI mode, the switching supply can use an inductor having a saturated core or having a reduced inductance
Data Source
AI summary
An implantable or other ambulatory medical device can include a magnetic field detector, such as configured to detect an intense magnetic field. In an example, the ambulatory or implantable medical device can include an inductive switching supply, such as including one or more of a peak current comparator, or a zero current comparator. In an example, the ambulatory or implantable medical device can include a controller circuit, configured to control a switch, such as to controllably charge an inductor included in the inductive switching supply.