title: Low-Cost High-Performance MRI.
abstract: Magnetic Resonance Imaging (MRI) is unparalleled in its ability to visualize anatomical structure and function non-invasively with high spatial and temporal resolution. Yet to overcome the low sensitivity inherent in inductive detection of weakly polarized nuclear spins, the vast majority of clinical MRI scanners employ superconducting magnets producing very high magnetic fields. Commonly found at 1.5-3 tesla (T), these powerful magnets are massive and have very strict infrastructure demands that preclude operation in many environments. MRI scanners are costly to purchase, site, and maintain, with the purchase price approaching $1 M per tesla (T) of magnetic field. We present here a remarkably simple, non-cryogenic approach to high-performance human MRI at ultra-low magnetic field, whereby modern under-sampling strategies are combined with fully-refocused dynamic spin control using steady-state free precession techniques. At 6.5 mT (more than 450 times lower than clinical MRI scanners) we demonstrate (2.5 × 3.5 × 8.5) mm(3) imaging resolution in the living human brain using a simple, open-geometry electromagnet, with 3D image acquisition over the entire brain in 6 minutes. We contend that these practical ultra-low magnetic field implementations of MRI (<10 mT) will complement traditional MRI, providing clinically relevant images and setting new standards for affordable (<$50,000) and robust portable devices.
authors.affiliation: MGH/A.A. Martinos Center for Biomedical Imaging, 149 13th St, Suite 2301, Charlestown MA 02129, USA.|Department of Physics, Harvard University, 17 Oxford St, Cambridge, MA 02138, USA.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Sarracanie
authors.affiliation: MGH/A.A. Martinos Center for Biomedical Imaging, 149 13th St, Suite 2301, Charlestown MA 02129, USA.|Department of Physics, Harvard University, 17 Oxford St, Cambridge, MA 02138, USA.
authors.forename: Cristen D
authors.initials: CD
authors.lastname: LaPierre
authors.affiliation: MGH/A.A. Martinos Center for Biomedical Imaging, 149 13th St, Suite 2301, Charlestown MA 02129, USA.|Department of Physics, Harvard University, 17 Oxford St, Cambridge, MA 02138, USA.|Institute of Physics of Biological Systems, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Najat
authors.initials: N
authors.lastname: Salameh
authors.affiliation: MGH/A.A. Martinos Center for Biomedical Imaging, 149 13th St, Suite 2301, Charlestown MA 02129, USA.|Department of Physics, Harvard University, 17 Oxford St, Cambridge, MA 02138, USA.|School of Physics, University of Sydney, Physics Rd, Sydney NSW 2006, Australia.
authors.forename: David E J
authors.initials: DEJ
authors.lastname: Waddington
authors.affiliation: MGH/A.A. Martinos Center for Biomedical Imaging, 149 13th St, Suite 2301, Charlestown MA 02129, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Witzel
authors.affiliation: MGH/A.A. Martinos Center for Biomedical Imaging, 149 13th St, Suite 2301, Charlestown MA 02129, USA.|Department of Physics, Harvard University, 17 Oxford St, Cambridge, MA 02138, USA.|Harvard Medical School, 25 Shattuck St, Boston, MA 02115, USA.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Rosen