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Calibration assessment in quantitative electroencephalographic brainmapping and evoked potential studies
A K Richards1, M A Hamilton-Bruce
1Department of Biomedical Engineering, Queen Elizabeth Hospital, Woodville, South Australia.
Australasian Physical & Engineering Sciences in Medicine
|September 1, 1994
Summary
This study validated quantitative electroencephalography (qEEG) and evoked potential (EP) equipment accuracy. Calibration testing revealed amplitude variations and potential scaling issues in topographic maps, highlighting the need for regular checks.
Area of Science:
- Neurophysiology
- Electrophysiology
- Medical Instrumentation
Background:
- Quantitative electrophysiological brain mapping techniques were introduced using a Cadwell Spectrum 32 system.
- The need for equipment validation to ensure accuracy and consistency in neurophysiological measurements.
Purpose of the Study:
- To ascertain the accuracy and consistency of quantitative electroencephalography (qEEG) and evoked potential (EP) equipment.
- To establish the performance limits of the hardware and software for quantitative and topographic data.
Main Methods:
- Calibration signal input and amplitude measurement for qEEG and EP in different montages.
- Synchronous calibration signal mapping at varying times.
- Re-analysis of previously selected electroencephalographic (EEG) epochs from control subjects.
Main Results:
- qEEG amplitudes varied between -5.4% and +5.8%.
- EP amplitudes varied by 9.5% or less, improving to 5.5% or less after a software upgrade.
- QEEG voltage mapping showed minimal color increment variation, potentially representing up to 25.2% of the scale.
Conclusions:
- Quantitative electrophysiological brain mapping systems require regular calibration checks with independent signal generators.
- Users must be aware that topographic map scaling can lead to erroneous conclusions in data interpretation.