title: Design of a mobile, homogeneous, and efficient electromagnet with a large field of view for neonatal low-field MRI.
abstract: OBJECTIVE
  In this work, a prototype of an effective electromagnet with a field-of-view (FoV) of 140 mm for neonatal head imaging is presented. The efficient implementation succeeded by exploiting the use of steel plates as a housing system. We achieved a compromise between large sample volumes, high homogeneity, high B0 field, low power consumption, light weight, simple fabrication, and conserved mobility without the necessity of a dedicated water cooling system.
  
  
  METHODS
  The entire magnetic resonance imaging (MRI) system (electromagnet, gradient system, transmit/receive coil, control system) is introduced and its unique features discussed. Furthermore, simulations using a numerical optimization algorithm for magnet and gradient system are presented.
  
  
  RESULTS
  Functionality and quality of this low-field scanner operating at 23 mT (generated with 500 W) is illustrated using spin-echo imaging (in-plane resolution 1.6 mm × 1.6 mm, slice thickness 5 mm, and signal-to-noise ratio (SNR) of 23 with a acquisition time of 29 min). B0 field-mapping measurements are presented to characterize the homogeneity of the magnet, and the B0 field limitations of 80 mT of the system are fully discussed.
  
  
  CONCLUSIONS
  The cryogen-free system presented here demonstrates that this electromagnet with a ferromagnetic housing can be optimized for MRI with an enhanced and homogeneous magnetic field. It offers an alternative to prepolarized MRI designs in both readout field strength and power use. There are multiple indications for the clinical medical application of such low-field devices.
authors: Research Center Magnetic-Resonance-Bavaria (MRB), Am Hubland, 97074, Würzburg, Germany. lother@mr-bavaria.de.
authors: Steffen
authors: S
authors: Lother
authors: Departments of Engineering Science and Mechanics, Neurosurgery, and Physics, Center of Neural Engineering, Penn State University, University Park, PA, USA.
authors: Steven J
authors: SJ
authors: Schiff
authors: High Field MRI Facility, Huck Institutes of the Life Sciences, Penn State University, University Park, PA, USA.|Department of Biomedical Engineering, Penn State University, University Park, PA, USA.
authors: Thomas
authors: T
authors: Neuberger
authors: Research Center Magnetic-Resonance-Bavaria (MRB), Am Hubland, 97074, Würzburg, Germany.|Department for Experimental Physics 5 (Biophysics), University of Wuerzburg, Würzburg, Germany.
authors: Peter M
authors: PM
authors: Jakob
authors: Research Center Magnetic-Resonance-Bavaria (MRB), Am Hubland, 97074, Würzburg, Germany.
authors: Florian
authors: F
authors: Fidler
mesh_terms: D000465:Algorithms; D031230:Ananas; D003198:Computer Simulation; D004867:Equipment Design; D006257:Head / Q000000981:diagnostic imaging*; D006801:Humans; D007231:Infant, Newborn; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008280:Magnetics; D059346:Magnets; D059629:Signal-To-Noise Ratio; D013232:Steel
chemical_list: D013232:Steel
keywords: Biplanar gradient system; Electromagnet; Low-field MRI; Neonatal MRI; Structural steel housing