Brain Mapping and Quantitative EEG (qEEG): What Clinicians Should Know

Most EEG machines today include "brain mapping" in their software. Understanding what these tools actually measure helps clinicians use them well and helps buyers judge the value of these features.

What is quantitative EEG?

Quantitative EEG (qEEG) converts EEG signals into numbers. The most common method is the Fast Fourier Transform (FFT), which breaks the signal into frequency bands (delta, theta, alpha, beta and gamma) and calculates the power in each band.

Common displays

• FFT spectra. Power plotted against frequency for each channel.
• Topographic brain maps. Colour-coded scalp maps of power in each band.
• CSA (Compressed Spectral Array). Spectra stacked over time, useful for spotting trends.
• DSA (Density Spectral Array). A colour-coded time-frequency display, popular for continuous ICU monitoring.

Systems such as the NEUROMAX NMX-32 and NMX-64 include FFT, CSA, DSA and mapping modules.

Clinical and research uses

• ICU trend monitoring. DSA and CSA help reviewers spot seizures or changes over long recordings.
• Encephalopathy and slowing. Quantifies diffuse or focal slowing.
• Research. Cognitive neuroscience, psychiatry and pharmaco-EEG studies.
• Neurofeedback. Some biofeedback programmes use qEEG measures. See our neurofeedback vs biofeedback article.

Limitations

• qEEG is very sensitive to artifacts, so clean recordings are essential.
• Maps need careful interpretation and should not be read on their own.
• Normative databases vary, so use them with caution.
• Visual review by a trained neurologist remains the clinical standard.

Does channel count matter?

Maps can be made from a standard 19–24 electrode montage. Higher-density EEG (64 channels) improves spatial resolution and source analysis, which matters for research and pre-surgical work.

If quantitative analysis is important to your department, ask us for a software demonstration before you buy. Contact RS Enterprises.