Toward High Resolution Images with SQUID-based Ultra-low
Field Magnetic Resonance Imaging

 Michelle Espy, Member, IEEE, Per Magnelind, Andrei Matlashov,
Shaun Newman, Algis Urbaitis, Petr Volegov

Abstract - Magnetic resonance imaging (MRI) is the state-of-the art clinical method for imaging soft-tissue anatomy. Because signal scales with the applied magnetic field, the overwhelming trend in MRI has been to high magnetic fields, typically 1.5 or 3 T. However, there has been recent interest in ultra-low field (ULF) MRI using 10-100 mT magnetic fields.  At ULF there are opportunities for novel imaging applications such as MRI combined with magnetoencephalography (MEG) in a single device, imaging through or in the presence of metal, and enhanced spin-lattice tissue contrast. Loss in signal is mitigated by sensitive detectors such as superconducting quantum interference devices (SQUIDs) and sample pre-polarization, typically from 10-100 mT. There have been several proof-of-concept demonstrations based on this approach. However, ULF MRI image quality still suffers from one or more of the following disadvantages compared to HF MRI:  lower signal-to-noise ratio, poor spatial resolution, and longer imaging time. Here we present recent progress toward “clinically relevant” ULF MRI parameters:  voxel SNR > 10, voxel size < 2×2×4 mm3.  Data and simulations from a single channel system are presented and discussed.

Keywords - SQUID MRI, ULF MRI, MEG, SQUID array.

IEEE/CSC & ESAS European Superconductivity News Forum (ESNF) No. 22 October/November 2012.  ESNF Reference No.ST325 Category 4.
The published version of this preprint appeared in IEEE Transactions on Applied Superconductivity 23, 1603107 (June 2013).