ultralowfield
Ultralow-field (ULF) refers to a regime of magnetic resonance conducted at extremely weak static magnetic fields, typically in the microtesla to tens of microtesla range, in contrast to conventional high-field MRI or NMR that use tesla-scale fields. In ULF, the Zeeman interaction is comparable to or smaller than spin-spin couplings, so spectra reflect J-couplings and other interactions rather than chemical shifts alone. ULF techniques include ultralow-field NMR and ultralow-field MRI, often using prepolarization in a strong field followed by transport to a shielded region where detection occurs at near-zero field.
Detection is usually performed with highly sensitive quantum sensors such as superconducting quantum interference devices (SQUIDs)
Historically, ULF emerged from interest in portable, low-cost magnetic resonance and from advances in quantum sensing.
Advantages of ultralow-field approaches include reduced equipment complexity, avoidance of cryogenics, and potential for safer, portable
Research continues to expand sensitivity, multi-nuclear capabilities (1H, 13C, 19F), and imaging speeds, with potential applications