As everyone knows from their introductory physics classes, a moving charge produces a magnetic field around itself. Electrons moving throughout the brain, from neuron to neuron, generate extremely weak magnetic fields that are very hard to detect, but that contain important information about what’s going on within the organ. Identifying the location where the magnetic fields are generated can help neurosurgeons treat patients with certain types of epilepsy, as current methods employing EEG and direct implantation of electrodes onto the brain have proven lacking.
At the National Institute of Standards and Technology (NIST), researchers are working on a magnetometer that would be able to detect magnetic fields only a few quadrillionths of a tesla. This should be sufficient to resolve the exact location of the tissues generating rogue signals that result in seizures, giving brain surgeons a precise tool to hone in on their targets.
Currently, the best magnetometers used in research and clinical practice are superconducting quantum interference devices, better known as SQUIDs. The problem with them is that they require to be cooled using liquid helium. They’re expensive, can be hard to support, and don’t yet provide the necessary accuracy for many applications.
NIST’s technology relies on microfabricated optically pumped magnetometers (µOPMs) that do not require cooling and can be placed right onto the scalp and accommodate any patient. The µOPMs work by detecting how the spin of rubidium atoms is altered by a magnetic field. The atoms are aligned using polarized laser light, and any deviation from this alignment caused by a magnetic field changes the intensity of the escaping light. By simply detecting the changes in this light is a measure of the intensity of the magnetic field that’s causing it to fluctuate.
So far NIST’s prototypes have approached the precision of SQUID systems, so now the team behind the project is aiming to beat and exceed what was previously possible.
Here’s a short video demonstrating the basic workings of the technology: