title: On concomitant gradients in low-field MRI.
abstract: Growing interest in magnetic resonance imaging (MRI) at ultra-low magnetic fields (ULF, approximately muT fields) has been motivated by several advantages over its counterparts at higher magnetic fields. These include narrow line widths, the possibility of novel imaging schemes, reduced imaging artifacts from susceptibility variations within a sample, and reduced system cost and complexity. In addition, ULF NMR/MRI with superconducting quantum interference devices is compatible with simultaneous measurements of biomagnetic signals, a capability conventional systems cannot offer. Acquisition of MRI at ULF must, however, account for concomitant gradients that would otherwise result in severe image distortions. In this paper, we introduce the general theoretical framework that describes concomitant gradients, explain why such gradients are more problematic at low field, and present possible approaches to correct for these unavoidable gradients in the context of a non-slice-selective MRI protocol.
authors.affiliation: Los Alamos National Laboratory, Biological and Quantum Physics Group, Los Alamos, NM 87545, USA.
authors.forename: P L
authors.initials: PL
authors.lastname: Volegov
authors.forename: J C
authors.initials: JC
authors.lastname: Mosher
authors.forename: M A
authors.initials: MA
authors.lastname: Espy
authors.forename: R H
authors.initials: RH
authors.lastname: Kraus
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D004574:Electromagnetic Fields; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008954:Models, Biological; D008956:Models, Chemical; D013113:Spin Labels
chemical_list: D013113:Spin Labels