CERMEP’s MEG department offers the neuroscience community a non-invasive technique for functional exploration of the human brain. By definition, Magnetoencephalography (MEG) is a functional brain imaging technology that involves recording live, close to the head, the magnetic fields generated by the brain’s neurons. The cerebral magnetic field is around 1 billion times weaker than the earth’s magnetic field, so the imager is placed in an examination room (a Faraday cage-type shielded room) to avoid being subjected to potential external magnetic fields.
CERMEP’s MEG imager consists of a special cryostat, a helmet covering the subject’s head and 275 SQUIDS (Superconducting QUantum Interference Device) magnetic flux sensors, enabling measurements with excellent spatial resolution and sub-millisecond temporal resolution. To achieve sufficient measurement sensitivity, these sensors are immersed in liquid helium at 4.2K (-269°C), the temperature at which their superconducting capabilities can be expressed. The department is equipped for auditory, visual, tactile and electrical sensory stimulation.
It is then expanded, purified, liquefied and stored in a 150-liter vacuum super-insulated tank (dewar) close to the MEG room, awaiting liquid transfer for top-up. The scrubber and liquefier installed use Pulse-Tube cryocoolers, offering high reliability, low maintenance and low vibration and noise levels. Helium liquefaction capacity was measured at 31 liters/day by Absolut System engineers, making CERMEP completely self-sufficient in helium management.