Active Magnetic Field Nulling for MEG Without Shielded Rooms
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Solution Overview
Problem
Current Magnetoencephalography (MEG) systems require expensive and cumbersome magnetically shielded rooms (MSRs) to null ambient magnetic fields, limiting their application, comfort for patients, and compatibility with other medical measurements due to the need for controlled, static environments.
Innovation Solution
A system using an array of magnetic field generating elements and sensing elements with a feedback control unit to actively null magnetic fields within a volume, mimicking super-diamagnetic principles, allowing for magnetic field cancellation without the need for MSRs, using orthogonal projection algorithms to efficiently calculate optimal electric currents for field nulling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If magnetically shielded rooms (MSR) are used to null ambient magnetic fields, then magnetic field nulling is achieved, but cost and device complexity increase significantly
Solution Approach 1:
The patent divides the magnetic field nulling function into discrete controllable components - multiple independent magnetic field generating elements (coils) arranged in arrays, each capable of being controlled individually through feedback signals. This segmented approach replaces the monolithic MSR structure with distributed, independently controllable units that collectively achieve field nulling.
Solution Approach 2:
The patent implements dynamic magnetic field nulling through real-time feedback control. Sensors continuously monitor the magnetic field environment and provide feedback signals that dynamically adjust the current in generating elements. This dynamic adaptation allows the system to respond to changing magnetic conditions without requiring a static, overly complex shielded structure.
2Object-affected harmful factors
If magnetically shielded rooms (MSR) are used to null ambient magnetic fields, then magnetic field nulling is achieved, but the system becomes less adaptable to different environments and patient comfort
Solution Approach 1:
The feedback-controlled generating elements enable the system to adapt to different environmental magnetic conditions in real-time. The dynamic adjustment of coil currents allows the same apparatus to function effectively in various locations (clinic, research lab, home environment) without requiring a fixed MSR infrastructure, thereby enhancing environmental adaptability.
Solution Approach 2:
The patent employs feedback control where sensors detect ambient magnetic field variations and generate feedback signals that automatically adjust the generating elements. This closed-loop system continuously adapts to changing environmental conditions, making the apparatus versatile across different settings while maintaining magnetic field nulling performance.
3Object-affected harmful factors
If magnetically shielded rooms (MSR) are used to null ambient magnetic fields, then magnetic field nulling is achieved, but calculation time and computational complexity increase
Solution Approach 1:
The patent performs preliminary calibration by determining the transfer function between generating elements and sensors before actual operation. This pre-computed relationship matrix enables real-time control calculations during measurement, significantly reducing computation time while maintaining accurate magnetic field nulling.
Solution Approach 2:
The patent replaces complex real-time iterative optimization with a pre-computed transfer function approach. By substituting the mechanical/iterative calculation process with a pre-determined mathematical relationship, the system achieves fast real-time control without excessive computational burden during actual MEG measurements.
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 enables the creation of a magnetic-field-free environment within a compact and cost-effective setup, allowing for more flexible and comfortable patient measurements, including concurrent MEG and MRI, while reducing magnetic fields by several orders of magnitude with high uniformity.
Implementation Method 1
a plurality of separate magnetic field generating elements placed at separate respective locations surrounding the nulling region for generating respective nulling magnetic fields extending into the nulling region
Implementation Method 2
a plurality of magnetic field sensing elements placed at a plurality of respective separate locations within the nulling region for sensing respective values of the magnetic field within the nulling region
Implementation Method 3
controlling the values of the respective nulling magnetic fields generated by each of the plurality of magnetic field generating elements in response to values of the magnetic field sensed by the plurality of magnetic field sensing elements by driving the magnetic field generating elements with respective electric currents that reduce the magnetic field values detected by respective magnetic field sensing elements to values not exceeding a pre-set threshold value
Data Source
AI summary
An apparatus for nulling a magnetic field within a nulling region in an external ambient magnetic field comprising a plurality of separate magnetic field generating elements 102 are located at separate respective locations surrounding the nulling region for generating respective nulling magnetic fields extending into the nulling region. A plurality of magnetic field sensing elements 103 are positioned at a plurality of respective separate locations within the nulling region for sensing respective values of the magnetic field within the nulling region. A feedback control unit 150 controls the values of the respective nulling magnetic fields generated by each of the plurality of magnetic field generating elements in response to values of the magnetic field sensed by the plurality of magnetic field sensing elements by driving the magnetic field generating elements with respective electric currents that reduce the magnetic field values detected by respective magnetic field sensing elements to values not exceeding a pre-set threshold value corresponding to a pre-set nulling of the magnetic field within the nulling region.