A miniature atom-based magnetic sensor has passed a significant research milestone by successfully measuring human brain activity. The sensor was developed by the US-based National Institute of Standards and Technology (NIST).
Experiments reported this week* verify that the sensor could potentially be used in biomedical applications like studying mental processes and understanding neurological diseases.
NIST, along with some German scientists used the sensor to measure alpha waves in the brain associated with somebody opening and closing their eyes and also to measure the signals resulting from stimulation of the hand. The measurements were verified by comparing them with signals recorded by a superconducting quantum interference device (SQUID). SQUIDs are considered the benchmark instruments for experiments of this type.
Right now, the NIST mini-sensors are less sensitive than SQUIDs. However, there is the potential that they will be able to achieve comparable performance and they offer advantages in the areas of size, portability and cost.
The results of the study show that the NIST mini-sensor may be useful in magnetoencephalography (MEG), a non-invasive procedure which measures the magnetic fields produced by electrical activity in the human brain. It is a tool used in basic research on perceptual and cognitive processes in healthy individuals; in screening of visual perception in newborn babies; and mapping brain activity before surgery to remove tumours or treat epilepsy. It is thought that MEG may also be useful in brain-computer interfaces.
At present, MEG currently relies on SQUID arrays mounted in heavy helmet-shaped flasks containing cryogenic coolants. This is necessary because SQUIDs work best at minus 269º C (4 º above absolute zero). The chip-scale NIST sensor is around the same the size as a sugar cube and it operates at room temperature, so it is hoped that it may enable lightweight flexible MEG helmets. And it would be cheaper to mass produce than typical atomic magnetometers, which are larger and harder to produce.
NIST co-author Svenja Knappe explained, "We're focusing on making the sensors small, getting them close to the signal source, and making them manufacturable and ultimately low in cost."
"By making an inexpensive system you could have one in every hospital to test for traumatic brain injuries and one for every football team."
Going forward, NIST scientists are hoping to boost the mini-sensor's performance about tenfold. According to their calculations, an enhanced sensor could match the sensitivity of SQUIDS.
* T.H. Sander, J. Preusser, R. Mhaskar, J. Kitching, L. Trahms and S. Knappe. Magnetoencephalography with a chip-scale atomic magnetometer. Biomedical Optics Express. Vol. 3, Issue 5, pp. 981–990. Published online April 17.