Date: 10/10/2012

Wireless active-electrode EEG headset offered by Imec, Holst Centre and Panasonic

Imec, Holst Centre and Panasonic have developed a new prototype of a wireless EEG (electroencephalogram) headset. Continuous impedance monitoring and the use of active electrodes increases the quality of EEG signal recording compared to former versions of the system. The data are transmitted in real-time to a receiver located up to 10m from the system.

The system integrates circuit level components including imec’s active electrodes and EEG amplifier together with a microcontroller and a low power radio. It is capable of continuously recording 8 channel EEG signals while concurrently recording electrode-tissue contact impedance (ETI). This simultaneous ETI recording provides continuous, remote assessment of electrode contact status during EEG recording. The active electrodes decrease the susceptibility of the system to power-line interference and cable motion artifacts, thus increasing signal quality. The system can be configured at run-time to modify the settings of the recordings including number of channels, or enabling/disabling the impedance recording. The autonomy of the system ranges from 22 hours (8 channels of EEG with ETI) to 70 hours (1 channel of EEG only).

The system has a high common-mode rejection ratio (>92 dB), low noise (<6 µVpp, 0.5-100Hz), DC offset tolerance of +/- 900mV and is AC coupled with configurable cut-off frequency. Sensitivity and dynamic range are configurable through a programmable gain stage (default 1.5mVpp and 366nV, respectively).The system (with dry electrodes and no skin preparation) is validated against a commercially available wired reference system (with wet electrodes and skin preparation), comparing the spectra between 1 and 30Hz. The high correlation coefficients (ranging from 0.81to 0.98 in four 1-minute recordings with eyes open) indicate that both systems have similar performance.

The heart of the system is the low-power (750µW) 8-channel EEG monitoring chipset. Each EEG channel includes two active electrodes and a low-power analog signal processor. The EEG channels are designed to extract high-quality EEG signals under a large amount of common-mode interference. The active electrode chips have buffer functionality with high input impedance (1.4GO at 10Hz), enabling recordings from dry electrodes, and low output impedance reducing the power-line interference without using shielded wires

The system is integrated into imec’s EEG headset with dry electrodes, which offers EEG recordings with minimal set-up time. The electronics system measures only 35 x 30 x 5 mm (excluding battery).

Industry can get access to imec’s technology for intelligent body area networks with wireless sensors, such as this EEG, by joining imec’s Human++ program as research partner or by licensing agreements for further product development. Within the Human++ program, imec and Holst Centre develop solutions for an efficient and better healthcare.

Source: Imec