Active Shimming for MRI Artifact Reduction
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Solution Overview
Problem
Magnetic resonance imaging (MRI) scanners face image distortion due to magnetic materials in electronic components within the magnet bore, which are difficult to replace and introduce significant artifacts, and power cables can couple with magnetic fields, causing further issues.
Innovation Solution
The implementation of electrically conductive loops or windings around electronic components, controlled by a magnetic field sensor and controller, to determine and generate magnetic field shim currents that compensate for distortions in the static magnetic field, effectively canceling out image artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard IC chips with magnetic materials are used inside the magnet bore, then device functionality and cost-effectiveness are maintained, but image distortion and artifacts are introduced
Solution Approach 1:
The patent measures the magnetic field distortion caused by the IC chip using a magnetic field sensor, then uses this information to calculate compensatory shim currents that are applied through conductive loops. This converts the harmful magnetic distortion into a measurable parameter that can be actively compensated, allowing standard magnetic-containing IC chips to be used without degrading image quality
Solution Approach 2:
The system implements a feedback loop where the magnetic field sensor continuously monitors the ambient magnetic field, the controller processes this information to determine the distortion caused by the IC chip, and adjusts the shim currents accordingly. This closed-loop feedback enables real-time compensation of magnetic field artifacts, maintaining image quality while using cost-effective standard IC chips
2Use of energy by moving object
If power cables are used to supply electricity to electronic components, then power delivery is achieved, but coupling with magnetic field gradients and RF signals causes additional artifacts and routing issues
Solution Approach 1:
The patent introduces an intermediary approach by using a magnetic field sensor to detect the magnetic field environment and a controller to calculate appropriate shim currents. This intermediary measurement and calculation system enables power delivery without direct cable coupling to magnetic field gradients, as the shim currents compensate for any residual coupling effects
Solution Approach 2:
The system converts the potential harmful effect of cable coupling into a measurable magnetic field distortion that can be compensated. By measuring the actual magnetic field environment and applying compensatory shim currents, the system transforms the cable coupling issue from an uncorrectable artifact source into a correctable parameter
3Device complexity
If batteries are used instead of power cables, then cable routing issues are avoided, but magnetic material in batteries introduces image distortion
Solution Approach 1:
The patent measures the magnetic field distortion caused by the battery using a magnetic field sensor, then uses this information to calculate compensatory shim currents. This converts the harmful magnetic distortion from the battery into a measurable and correctable parameter, allowing batteries to be used without degrading image quality
Solution Approach 2:
The system implements feedback by continuously monitoring the magnetic field with the sensor, processing the measurements to determine battery-induced distortion, and adjusting shim currents in real-time. This enables the use of batteries for simplified power delivery while maintaining image quality through active compensation
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 significantly reduces image artifacts caused by magnetic components, allowing for effective shimming of the magnetic field to restore its undistorted state, improving image quality without the need for custom-made nonmagnetic IC chips or batteries.
Implementation Method 1
a magnetic field sensor configured to measure an ambient magnetic field measurement signal
Implementation Method 2
at least one electrically conductive loop or winding disposed around the electronic component... energize the at least one electrically conductive loop or winding to flow the determined at least one magnetic field shim current
Data Source
AI summary
An electronic device (10) includes an electronic component (14); at least one electrically conductive loop or winding (18) disposed around the electronic component; and an electronic controller (24) configured to: obtain (102) a magnetic field direction from a received ambient magnetic field measurement signal; determine (104) at least one magnetic field shim current based on the obtained magnetic field direction; and energize (106) the at least one electrically conductive loop or winding to flow the determined at least one magnetic field shim current.