High-Tc SQUID vs. low-Tc SQUID-based recordings on a head phantom: Benchmarking for magnetoencephalography

Journal article, 2015

We explore the potential that high critical-temperature (high-Tc) superconducting quantum interference device (SQUID) technology has for magnetic recordings of brain activity, i.e., magnetoencephalography (MEG). To this end, we performed a series of benchmarking experiments to directly compare recordings with a commercial (low-Tc SQUID-based) 306-channel MEG system (Elekta Neuromag TRIUX, courtesy of NatMEG) and a single channel high-Tc SQUID system. The source on which we recorded is a head phantom including 32 artificial current dipoles housed inside a half-spherical shell (courtesy Elekta Oy) for calibrating MEG systems. The high-Tc SQUID magnetometer consisted of a single layer YBa2Cu3O7-x (YBCO) film on a 10 mm × 10 mm bicrystal substrate with a magnetic field sensitivity of ~40 fT/Hz down to 10 Hz. We recorded serial activations of eight tangential current dipoles located at different depths from the surface of the head phantom. Results indicate that our individual high-Tc SQUID demonstrated signal-to-noise ratios (SNRs) about 7-14 times lower than that of similarly-positioned low-Tc SQUIDs in a commercial MEG system. Only considering single-channel SNR, high-Tc SQUIDs with resolution better than 18 fT/Hz would be required to outperform the low-Tc system for shallow dipole sources. This work demonstrates a proof of principle study for future multichannel high-Tc MEG system development.