SQUID-based simultaneous detection of NMR and biomagnetic signals at ultra-low magnetic fields

Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) at ultra-low magnetic fields (ULF, fields of ∼μT) have several advantages over their counterparts at higher magnetic fields. These include narrow line widths, the possibility of novel imaging schemes such as T₁ weighted images, and reduced system cost and complexity. In addition, ULF NMR/MRI with superconducting quantum interference devices (SQUIDs) is compatible with simultaneous measurements of biomagnetic signals, a capability conventional systems cannot offer. SQUID-based ULF MRI has already been demonstrated, as have measurements of simultaneous MEG and NMR at ULF. In this paper we will show simultaneous magnetocardiography (MCG) and magnetomyography (MMG) with NMR are also possible. Another compelling application of NMR/MRI at ULF is the possibility of directly measuring magnetic resonance consequences of neuronal signals. In this paper we explore simultaneous MMG/NMR and MCG/NMR for an effect on the NMR signal, in T₂^*, that might be associated with the effects of bioelectric currents.