Spinoff of CEA-Leti Grenoble
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The quantum technology embedded within MAG4Health MEG was first developed for Space applications at CEA and sent in space in 2013 to map the Earth magnetic field. Sensors are still working after 8 years!
The technology is called helium optically-pumped magnetometers. The sensitive element of the sensor is a helium gas cell in which a plasma allows the excitation of billions of atoms which behave as small magnets. A laser and radiofrequency fields impose a synchronized behavior to these magnets such that they all contribute to a global signal which allow a measurement of the tiny magnetic fields emitted by the brain.
Helium is a noble gas, very stable over time, and has demonstrated its robustness and lifetime in Space magnetometry.
64 sensors are deployed within the helmet offering adaptability to any morphology. Once installed, the sensors automatically localize themselves with respect to each other, taking advantage of their capability to create and measure magnetic fields to compute their relative distances and orientations.
MAG4Health has an exclusive license to 10 CEA patents.
Functional magnetic resonance imaging (fMRI) images the brain activity by measuring the oxygenation level within the brain. This technique assumes that oxygen consumption is increased in the active brain regions (neurovascular coupling). fMRI is predominantly used to localize brain functions prior to surgery.
MEG provides a direct measurement of the brain activity through the electrical currents produced by neuronal activity. Thus the image of brain activity produced does not rely on any hypothesis. Specifically MEG is not subject unlike fMRI to the disturbances in the neurovascular coupling involved in most brain diseases, particularly in brain tumors. Moreover, MEG has much higher time resolution than fMRI, providing a precise temporal and spatial location of the brain activity.
EEG measures the electrical activity from the brain, with electrodes positioned on the patient’s scalp. The signal recorded by EEG and MEG has the same origin: the electrical currents in the brain. However, the EEG signal is attenuated and spatially blurred, notably due the human skull, which is electrically resistive. In contrast, the magnetic field measured by MEG is not affected by the skull and other tissues. Therefore, MEG is able to localize with millimetric accuracy the brain activity. In some cases, EEG and MEG can be used simultaneously and provide complementary information.
Single photon emission computed tomography (SPECT) and positron emission tomography (PET) are both nuclear imaging techniques. Thanks to a radioactive tracer injected to the patient, they image how blood flows to specific regions of the brain. These techniques deliver 3D images of the brain activity but averaged over a few minutes. Similarly to fMRI, SPECT and PET relie on the hypothesis that cerebral blood flow and neuronal activity are coupled.
Since it directly measures the electrical currents in the brain MEG has much better time resolution than SPECT and PET. SPECT and PET are based on a radioactive tracer, which exposes the patient to ionizing radiation. In contrast, MEG is fully non-invasive and can be used to diagnose pregnant women, babies and children.
Intracerebral electroencephalography (iEEG) consists in implanting EEG electrodes inside or at the very surface of the brain. Therefore, this method requires a brain surgery. Like EEG, iEEG measures electrical activity but inside the brain, which avoids the distortion due to the skull. Thus, iEEG provides much more accurate spatial information than EEG. However, iEEG cannot be used for all brain areas and is highly invasive.
In contrast, MEG can record the activity of the entire brain in a quick and non-invasive scan and allows for an accurate location of the brain activity.
If you are interested by this technology, its clinical applications, or if you wonder how to join this adventure...
Spinoff of CEA-Leti Grenoble