Whole-head SQUID system in a superconducting magnetic shield

Area of Science:

• Biophysics
• Neuroscience
• Materials Science

Background:

• Magnetoencephalography (MEG) traditionally relies on magnetically shielded rooms.
• Achieving high sensitivity, especially at low frequencies, remains a challenge for current MEG systems.
• Superconducting magnetic shields offer a potential alternative for enhanced magnetic field detection.

Purpose of the Study:

• To construct and evaluate a mobile whole-head SQUID system within a superconducting magnetic shield.
• To compare the sensitivity of SQUID sensors in this new shield versus a conventional shielded room.
• To assess the system's capability in detecting subtle neurological signals.

Main Methods:

• Construction of a mobile whole-head SQUID system utilizing a high-Tc superconductor (BSCCO) magnetic shield.
• Comparison of noise spectra from SQUID sensors (SNS Josephson junctions) within the superconducting shield and a Permalloy shielded room.
• Testing the system by observing somatosensory evoked potentials from median nerve stimulation.

Main Results:

• The SQUID system in the superconducting magnetic shield demonstrated over 100 times greater sensitivity below 1 Hz compared to a Permalloy shielded room.
• The system successfully detected somatosensory evoked signals, revealing monotonic rhythms persisting beyond 250 ms.
• Narrow rhythm nodes at longer latencies indicated the system's low-noise characteristics at low frequencies.

Conclusions:

• The mobile whole-head SQUID system in a superconducting magnetic shield significantly enhances sensitivity, particularly for low-frequency brain activity.
• This technology allows for the detection of subtle, high-level brain functions indicated by late somatosensory responses.
• The system holds promise for DC magnetoencephalography (MEG) applications, studying slow brain activities and functions.