Brain imaging in itself is not a new concept, with the first such technique being used as early as in 1880s; but the difference now is that physicists have in 2019 figured out a way to eliminate the need for the patient to stay completely still during the procedure by building a MEG (Magnetoencephalography) scanner.
(A two-year old child wearing the bike helmet style MEG scanner )
How does a MEG scanner work?
Neurons (brain cells) interact with one another by producing small electrical voltages, the net effect of which generates a magnetic field. While the magnitude of the field associated with a single neuron is insignificant, the result of many neurons (for example, 50,000 - 100,000) being excited simultaneously in a specific area of the brain produces a magnetic field strong enough to be recorded outside of the head.
In order to be able to capture such a small signal, big bulky MEG scanners use SQUID (superconducting quantum interference device) sensors, which have to be bathed in a large liquid helium cooling unit at approximately -269 °C; but new, portable MEG scanners use OPM sensors – optically pumped magnetometers, which don't need to be supercooled. Analysis of the signal patters recorded by these sensors can show the location, strength and orientation of the sources.
Future applications of MEG scanners in research
The brain undergoes numerous, significant changes during the first decades of a child's life, that includes both functional and structural changes. Although these are the critical times regarding brain development, relatively little is known about the process and the changes that are occurring; the main reason being the lack of appropriate equipment that would allow further research on a child's brain.
Non-invasive imaging techniques can provide information on brain structure and function, but still there are a couple of issues. First being that brain scanners tend to be optimized for adult-sized heads, but the other and much more important reason being that traditional scanners require patients to be completely still during the procedure and you can see how that would pose a problem for children.
This is why the MEG scanner is so important, by eliminating the need for the patient to be still during the procedure it makes it much applicable to children. Its application could lead to more discoveries regarding brain maturation and allow for better understanding and treatment of some diseases.
Because the new system is wearable, it allows scientists to undertake new kinds of experiments, with patients doing things that they can’t do in traditional brain scanners. For example, like bouncing a ping pong ball on a bat. Even a simple example like this one would allow a new way for neuroscientists to investigate coordination between the brains visual and movement centres.
The application of MEG scanners in medicine
MEG scanner is being used to better localize responses to stimuli, such as auditory or visual stimuli, in the brain. This can provide better quality information which can be used in the treatment of an individual as well as in future research in the quest of understanding the human brain. Recent studies have shown that MEG could, in the future, be used in diagnostics because of its ability to distinguish healthy control patients from those with conditions such as MS (Multiple Sclerosis), Alzheimer¢s disease, Schizophrenia, chronic alcoholism etc.
The clinical uses of MEG are in detecting and localizing pathological activity in patients with epilepsy, and in localizing eloquent cortex (area of the cortex that –if removed- will cause loss of sensory processing, linguistic ability or paralysis) in patients with brain tumors or epilepsy (if they wish to have surgery to treat it). Knowing the exact position of such areas is of great importance since it helps to avoid surgically induced neurological damage.
(D) MEG results for a 4-year-old boy with tuberous sclerosis and refractory focal epilepsy (daily seizures) showing a focal cluster of epileptic sources at the level of a right mesial parietal tuber. (E) Flair MRI showing the multiple cortical tubers. (F) Post-operative MRI showing the resection cavity of the right mesial parietal tuber.
The main difference between MEG and EEG
MEG (Magnetoencephalogram) sees a window of brain activity (tangential fields) with more sensitivity and clarity than EEG; the localization of that activity with source models is more accurate.
EEG (Electroencephalogram) sees a more complete picture of brain activity (tangential and radial fields), but less clearly than MEG. While the localization with EEG source models is less precise, you get more complete orientation information than with MEG.
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