MEG DC Signal Separation via Head Movement Monitoring

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Solution Overview

Problem

Current methods for measuring DC fields in biomagnetic signals are hindered by interference from immovable magnetic articles and patient movement, requiring complex setups and patient restraint, which are unsuitable for clinical measurements.

Innovation Solution

A method that monitors and corrects for head movement, allowing DC signals from a moving subject to be processed as static components, using spherical harmonic functions to separate physiological DC signals from interference, enabling free head movement and eliminating the need for specific test arrangements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a bed is moved sinusoidally to make DC currents visible in the measurement signal, then DC signals can be detected, but the magnetisation of the bed produces a strong interference signal that must be eliminated

Engineering Contradiction:

ImproveDC signal detection capabilityVSAvoidinterference signal from bed magnetisation

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent extracts and removes the interference signal component from the measurement system by measuring the bed's magnetisation separately (without the testee) and subtracting it from the total measurement signal, thereby eliminating the harmful interference while preserving the physiological DC signals

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a reference measurement as an intermediary - a separate measurement of the bed's magnetisation is taken and used as a reference signal to identify and eliminate the interference component in the actual measurement signal

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the testee is moved with respect to the measuring instrument to perceive physiological DC currents, then DC signals become visible, but the head movement must be controlled and restrained which complicates the measurement setup

Engineering Contradiction:

ImproveDC current measurement capabilityVSAvoidmeasurement setup complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical bed movement system with a computational approach - head movement is monitored using sensors (e.g., position sensors, accelerometers) and the movement data is used to correct the measurement signal mathematically, eliminating the need for mechanical displacement of the testee or bed

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The measurement system monitors its own operational state (head position/movement) and uses this self-diagnostic information to automatically correct the measurement signal, making the system self-regulating and eliminating the need for external mechanical intervention

Inventive Principle:

Principle #25Self-service

3Ease of operation

If head movement is monitored and corrected to process DC signals as static components, then measurement simplicity is improved, but signal processing complexity increases

Engineering Contradiction:

Improvemeasurement procedure simplicityVSAvoidsignal processing complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent performs preliminary correction of the measurement signal by compensating for head movement effects before final signal analysis - the movement correction is applied in advance to transform dynamic DC signal components into static equivalents, simplifying subsequent interpretation

Inventive Principle:

Principle #10Preliminary action

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 allows for effective measurement and separation of physiological DC fields without additional interference, facilitating real-time monitoring and reducing the complexity of DC field measurements in MEG and MKG applications.

Implementation Method 1

magnetometers such as SQUID sensors are usually used, which are sensitive just to dynamic phenomena

Methodology Applied

Scientific EffectMagnetic field detection: Magnetic Field

Implementation Method 2

separating a direct current component from the measurement signal on the basis of spherical harmonic functions

Methodology Applied

Scientific EffectSpherical harmonic decomposition:

Data Source

PatentUS8229540B2Method for separating multichannel signals produced by AC and DC sources from one another

Publication Date: 2012.07.24 MEGIN OY

AI summary

The present invention relates to a novel manner of measuring DC fields using a multi-channel MEG or MKG measuring instrument; and on the other hand, to a manner of eliminating from the measurement result the interference signals caused by the DC currents. The invention combines the monitoring system of a testee's movement and the method for motion correction of the measured signals so that the signals produced by the DC currents of a moving testee's are visible in the final measurement result as a static signal component in a conventional MEG or MKG measurement. In that case, in the measurement, it is not necessary to beforehand prepare oneself for measuring the DC fields.