Active Magnetic Shielding With Feedback for MEG Field Distortion
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Solution Overview
Problem
Existing magnetic shielding systems, particularly for magnetoencephalography (MEG), face challenges in effectively canceling external magnetic interference while allowing for subject movement and flexibility, due to interactions between active shielding coils and high-permeability materials, leading to distorted fields and limited dynamic range.
Innovation Solution
An active magnetic shield system comprising an array of magnetic field sensors and elements with unit coils arranged in multiple planes, combined with a passive shield, uses a feedback algorithm to generate a controlled magnetic field pattern, minimizing remnant fields and signal loss during subject movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional passive shields with fixed coil arrangements are used, then magnetic field shielding is provided, but the system lacks flexibility for subject movement and the field pattern becomes distorted due to interactions with high-permeability materials
Solution Approach 1:
The patent implements dynamic coil current adjustment through a feedback control system that continuously monitors the magnetic field and modifies coil currents in real-time. This allows the shielding system to adapt to subject movement while maintaining accurate field patterns, resolving the contradiction between flexibility and precision.
Solution Approach 2:
A feedback control system using magnetic field sensors and controllers monitors the actual magnetic field environment and adjusts coil currents accordingly. This feedback mechanism compensates for field distortions caused by high-permeability materials and enables flexible subject movement while maintaining precise field control.
2Object-affected harmful factors
If active shielding coils are added to cancel external magnetic fields, then field cancellation capability is improved, but interactions with high-permeability materials cause distorted fields and limited dynamic range
Solution Approach 1:
The feedback control system continuously monitors magnetic field conditions and adjusts coil currents to compensate for distortions caused by interactions with high-permeability materials. This ensures reliable field cancellation without the distortion problems that would otherwise limit dynamic range.
Solution Approach 2:
The system dynamically changes coil current parameters based on real-time magnetic field measurements and environmental conditions. This allows the active shielding to maintain effective field cancellation while adapting to prevent distortion from material interactions.
3Object-affected harmful factors
If multiple layers of high-permeability material are used for passive shielding, then shielding effectiveness is improved, but the system becomes more complex and interacts adversely with active shielding coils
Solution Approach 1:
The feedback control system compensates for the complex interactions between active coils and multi-layer passive shielding by continuously monitoring field conditions and adjusting coil currents. This maintains shielding effectiveness while managing the complexity through intelligent control rather than simpler passive designs.
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 system provides flexible and effective magnetic field cancellation across a variable volume, enhancing signal integrity by dynamically adjusting the magnetic field to match target patterns, suitable for applications like MEG and MRI.
Implementation Method 1
each unit coil comprising a coil wire path arranged to produce a vector magnetic field pattern
Implementation Method 2
An array of magnetic field sensors arranged to sense a local magnetic field
Implementation Method 3
typically constructed from two or more layers of a material with a high magnetic permeability (e.g. a nickel-iron alloy such as mu-metal)
Implementation Method 4
A feedback algorithm arranged for controlling the current source for each unit coil to minimise the sensed local magnetic field
Data Source
AI summary
An active magnetic shield system, including an array of magnetic field sensors arranged to sense a local magnetic field. An array of magnetic field elements are arranged produce a magnetic field. Each magnetic field element has a unit coil for mounting to a plurality of surfaces arranged in at least 3 planes to define an enclosed cancellation volume, and to produce a vector magnetic field pattern.