At this week’s Medical Device & Manufacturing conference and exhibition
in Anaheim, imec and Holst
Centre present breakthroughs in enabling technologies for wireless EEG (electroencephalogram)
systems enabling continuous ambulatory monitoring. The demonstrated EEG headset
is compatible with dry electrodes and combines ease-of-use with ultra-low power
electronics. The prototype headset records high quality EEG signals and wirelessly
transmits the data in real-time to a receiver located up to 10m from the system.
Applications that can be envisaged with this EEG prototype system include entertainment
and infotainment, for example adaptive game environment reacting to the player’s
cognitive state, or e-learning where the difficulty can be adapted based on
cognitive load; lifestyle, such as neuro-feedback; safety, for example monitoring
drowsiness of drivers or cognitive load of occupational health services in action;
and medical such as early warning system for epileptic patients or brain typing
enabling people with motoric disabilities to communicate.
At the heart of the system is imec’s 8-channel ultra-low-power analog
readout ASIC (application-specific integrated circuit). The ultra-low power
readout ASIC consumes only 200µW and features high common mode rejection
ratio (CMRR) of 120dB and low noise (input referred noise of 55nV/vHz). These
performances are achieved at high input impedance (1GO), which makes it compatible
with the use of dry electrodes. The electronics, including ASIC, radio, and
controller chips are integrated in a small wireless EEG system of 25mmx35mmx5mm
dimensions, that can easily be embedded in headsets, helmets or other accessories.
The signal to noise ratio of the system is 25dB on real EEG signals. The entire
system consumes only 3.3mW for continuous recording and wireless transmission
of 1 channel, and 9.2mW for 8 channels. This gives between 1.5 to 4 days of
autonomy on a small 100mAh Li-ion battery, depending on the mode of operation.
Today’s EEG recordings are performed in hospital or lab settings, and
require trained personnel to apply the electrodes with gel. Taking EEG to the
home environment requires a system using dry electrodes, that is easy to set
up by the user and does not require recharging the battery every few hours.
To that purpose, the wireless EEG system has been integrated in a prototype
EEG headset. The prototype headset can be easily adapted to the head of the
user by extending a plastic bridge near the back of the head and by moving the
part that contains the electronics upwards or downwards. On top of that, a spring
suspension, guaranteeing improved robustness, and a magnetized pivoting mechanism
can be used for fine adaptation to the head. The magnetic connection of the
electrodes allows quick and easy replacement making it a hygienic solution.
Gel injection is still possible if required for certain applications. Today
the system relies on commercial off-the-shelf Ag/AgCl electrodes, which may
lead to certain level of discomfort. In a few years, research on dry electrodes
will result in increased comfort and higher signal quality. Combined with circuit
and algorithm innovation, this will eventually enable monitoring brain waves
Industry can get access to this technology by joining the 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. Intelligent body area networks with wireless sensors,
such as this EEG, promise to be a solution for more comfortable healthcare systems.
This will allow ambulatory monitoring of people, which increases the comfort
level of patients and is a cost- and time-efficient alternative for current
EEG monitoring systems. And, home monitoring results in daily life measurements
that cannot be measured in a clinical environment.
Posted February 8th, 2011