APPLIED PHYSICS: Warming Up Neuroimaging

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Science  15 Dec 2006:
Vol. 314, Issue 5806, pp. 1661b
DOI: 10.1126/science.314.5806.1661b

Superconducting quantum interference devices, or SQUIDs, are remarkably sensitive instruments for detecting small magnetic fields. When placed in an array in a helmet-like structure, they can even be used to detect the minute magnetic fields given off by the human brain. However, these neuroimaging machines tend to be large and expensive, in part because they require the SQUIDs to be held constantly at cryogenic liquid helium temperatures.

Recent work has shown that certain atomic gases are also sensitive to small magnetic fields and can be used to detect the fields given off by the heart. By refining this technique, Xia et al. have succeeded in measuring the hundredfold-weaker magnetic signals emerging from the brains of human test subjects. A cloud of potassium atoms isolated in a gas cell is optically excited, effectively rendering each atom an individual compass needle. The presence of a magnetic field then causes the atoms to precess, which in turn induces optical rotation of a probe beam used to quantify the field. The measurement matches the sensitivity of the low-temperature SQUIDs without the need for cryogenic cooling. — ISO

Appl. Phys. Lett. 89, 211104 (2006).

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