Editing Magnetoencephalography (section)

== History ==
[[Image:MIT EarlyYEARS-261 croped.tif|thumbnail|250px|left|Dr. Cohen's shielded room at MIT, in which first MEG was measured with a SQUID]]
[[Image:MIT EarlyYears-233a.jpg|thumbnail|500px|left|First MEG measured with SQUID, in Dr. Cohen's room at MIT]]
MEG signals were first measured by University of Illinois physicist [[David Cohen (physicist)|David Cohen]] in 1968,<ref name="cohen1">{{cite journal | vauthors = Cohen D | title = Magnetoencephalography: evidence of magnetic fields produced by alpha-rhythm currents | journal = Science | volume = 161 | issue = 3843 | pages = 784–6 | date = August 1968 | pmid = 5663803 | doi = 10.1126/science.161.3843.784 | bibcode = 1968Sci...161..784C | s2cid = 34001253 }}</ref> before the availability of the [[SQUID]], using a copper induction coil as the detector. To reduce the magnetic background noise, the measurements were made in a magnetically shielded room. The coil detector was barely sensitive enough, resulting in poor, noisy MEG measurements that were difficult to use. Later, Cohen built a much better shielded room at MIT, and used one of the first SQUID detectors, just developed by [[James Edward Zimmerman|James E. Zimmerman]], a researcher at Ford Motor Company,<ref>{{cite journal | vauthors = Zimmerman JE, Theine P, Harding JT |title=Design and operation of stable rf-biased superconducting point-contact quantum devices, etc|journal=Journal of Applied Physics|year= 1970|volume=41|issue=4|pages=1572–1580|doi=10.1063/1.1659074|bibcode=1970JAP....41.1572Z }}</ref> to again measure MEG signals.<ref>{{cite journal | vauthors = Cohen D | title = Magnetoencephalography: detection of the brain's electrical activity with a superconducting magnetometer | journal = Science | volume = 175 | issue = 4022 | pages = 664–6 | date = February 1972 | pmid = 5009769 | doi = 10.1126/science.175.4022.664 | url = http://davidcohen.mit.edu/sites/default/files/documents/1972ScienceV175(SquidMEG).pdf | bibcode = 1972Sci...175..664C | s2cid = 29638065 }}</ref> This time the signals were almost as clear as those of [[Electroencephalography|EEG]]. This stimulated the interest of physicists who had been looking for uses of SQUIDs. Subsequent to this, various types of spontaneous and evoked MEGs began to be measured.

At first, a single SQUID detector was used to successively measure the magnetic field at a number of points around the subject's head. This was cumbersome, and, in the 1980s, MEG manufacturers began to arrange multiple sensors into arrays to cover a larger area of the head.<ref>Yamamoto T, Williamson SJ, Kaufman L, Nicholson C, Llinas R: Magnetic localization of neuronal activity in the human brain. Proc Natl Acad Sci 85:8732-8736,1988[9]</ref> Present-day MEG arrays are set in a helmet-shaped [[vacuum flask]] that typically contain 300 sensors, covering most of the head.  In this way, MEGs of a subject or patient can now be accumulated rapidly and efficiently.

Recent developments attempt to increase portability of MEG scanners by using [[SERF|spin exchange relaxation-free]] (SERF) magnetometers. SERF magnetometers are relatively small, as they do not require bulky cooling systems to operate. At the same time, they feature sensitivity equivalent to that of SQUIDs. In 2012, it was demonstrated that MEG could work with a chip-scale atomic magnetometer (CSAM, type of SERF).<ref>{{cite journal | vauthors = Sander TH, Preusser J, Mhaskar R, Kitching J, Trahms L, Knappe S | title = Magnetoencephalography with a chip-scale atomic magnetometer | journal = Biomedical Optics Express | volume = 3 | issue = 5 | pages = 981–90 | date = May 2012 | pmid = 22567591 | pmc = 3342203 | doi = 10.1364/BOE.3.000981 }}</ref> More recently, in 2017, researchers built a working prototype that uses SERF magnetometers installed into portable individually 3D-printed helmets,<ref name="Boto_2018" /> which they noted in interviews could be replaced with something easier to use in future, such as a bike helmet.