New mini-sensor may be the future of non-invasive biomedical tests
A tiny sensor that can detect magnetic field changes as small as 70 femtoteslas—equivalent to brain waves of a person daydreaming—was demonstrated at the National Institute of Standards and Technology (NIST), and described in the November issue of Nature Photonics.
The sensor could be battery-operated and reduce the costs of non-invasive biomagnetic measurements, such as fetal heart monitoring.

Vishal Shah, and colleagues displayed the prototype device, which is almost 1,000 times more sensitive than NIST's original chip-scale magnetometer shown in 2004.

The new NIST mini-sensor could reduce the equipment size and costs associated with some non-invasive biomedical tests. The NIST group and collaborators have used a modified version of the original sensor to detect magnetic signals from a mouse heart, according to presentation by Brad Lindseth and colleagues at the University of North Carolina in Durham, N.C.

The developers said the new sensor is powerful enough for fetal heart monitoring. The designers said that in the future, the sensitivity can likely be improved to a level in the 10 femtotesla range, sufficient for additional applications such as measuring brain activity. A femtotesla is one quadrillionth (or a millionth of a billionth) of a tesla, the unit that defines the strength of a magnetic field.

The developers believe that the NIST device could be used in heart monitoring, known as magnetocardiography (MCG), which is sensitive enough to measure fields of few picoteslas emitted by the fetal heart from small currents in heart muscle cells. With further improvements, the developers believe that the NIST sensor could also be used in magnetoencephalography (MEG), which measures the magnetic fields produced by electrical activity in the brain, to pinpoint tumors or determine functionality of the brain.

MCG and MEG often do not require contrast agents or injected tracers like other medical procedures, such as MRI or PET.

NIST collaborators are also interested in making a portable MEG helmet that could be worn by epileptics to record brain activity before and during seizures.