Design of a mobile, homogeneous, and efficient electromagnet with a large field of view for neonatal low-field MRI

  • Steffen LotherEmail author
  • Steven J. Schiff
  • Thomas Neuberger
  • Peter M. Jakob
  • Florian Fidler
Research Article



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.

Materials and 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.


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.


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.


Electromagnet Neonatal MRI Structural steel housing Biplanar gradient system Low-field MRI 



We thank Toni Drießle for helpful discussions and permanently valuable engineering inputs.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical standards

This article does not contain any studies with human or animal subjects.


  1. 1.
    Blümich B, Casanova F, Appelt S (2009) NMR at low magnetic fields. Chem Phys Lett 477(4–6):231–240CrossRefGoogle Scholar
  2. 2.
    Stepisnik J, Erzen V, Kos M (1990) NMR imaging in the earth’s magnetic field. Magn Reson Med 15(3):386–391CrossRefPubMedGoogle Scholar
  3. 3.
    Mohoric A, Planinsic G, Kos M, Duh A, Stepisnik J (2004) Magnetic resonance imaging system based on earth’s magnetic field. Instrum Sci Technol 32(6):655–667CrossRefGoogle Scholar
  4. 4.
    Mohoric A, Stepisnik J, Kos K, Planinsic G (1999) Self-diffusion imaging by spin echo in earth’s magnetic field. J Magn Reson 136(1):22–26CrossRefPubMedGoogle Scholar
  5. 5.
    Appelt S, Kühn H, Häsing W, Blümich B (2006) Chemical analysis by ultrahigh-resolution nuclear magnetic resonance in the earth’s magnetic field. Nat Phys 2:105–109CrossRefGoogle Scholar
  6. 6.
    Appelt S, Häsing FW, Kühn H, Perlo J, Blümich B (2005) Mobile high resolution xenon nuclear magnetic resonance spectroscopy in the earth’s magnetic field. Phys Rev Lett 94(19):197602CrossRefPubMedGoogle Scholar
  7. 7.
    Halse ME, Coy A, Dykstra R, Eccles C, Hunter M, Ward R, Callaghan PT (2006) A practical and flexible implementation of 3D MRI in the earth’s magnetic field. J Magn Reson 182(1):75–83CrossRefPubMedGoogle Scholar
  8. 8.
    Kegler C, Seton HC, Hutchison JMS (2007) Prepolarized fast spin-echo pulse sequence for low-field MRI Magnetic Resonance in Medicine. Magn Reson Med 57(6):1180–1184CrossRefPubMedGoogle Scholar
  9. 9.
    Savukov I, Karaulanov T, Castro A, Volegov P, Matlashov A, Urbatis A, Gomez J, Espy M (2011) Non-cryogenic anatomical imaging in ultra-low field regime: hand MRI demonstration. J Magn Reson 211(2):101–108CrossRefPubMedPubMedCentralGoogle Scholar
  10. 10.
    Lother S, Hoelscher U, Kampf T, Jakob P, Fidler F (2013) 3D gradient system for two B0 field directions in Earth´s field MRI. Magn Reson Mater Phy 26(6):565–573CrossRefGoogle Scholar
  11. 11.
    Matter NI, Scott GC, Venook RD, Ungersma SE, Grafendorfer T, Macovski A, Conolly SM (2006) Three-dimensional prepolarized magnetic resonance imaging using rapid acquisition with relaxation enhancement. Magn Reson Med 56(5):1085–1095CrossRefPubMedGoogle Scholar
  12. 12.
    Savnik A, Malmskov H, Thomsen HS, Bretlau T, Graff LB, Nielsen H, Danneskiold-Samsøe B, Boesen J, Bliddal H (2001) MRI of the arthritic small joints: comparison of extremity MRI (0.2 T) vs high-field MRI (1.5 T). Eur Radiol 11(6):1030–1038CrossRefPubMedGoogle Scholar
  13. 13.
    Feynman R, Leighton R, Sands M (2006) The Feynman lectures on physics, vol II. Addison-Wesley, Reading. ISBN 0-8053-9047-2 (Chapter 37: Magnetic Materials)Google Scholar
  14. 14.
    Wright SM, Brown DG, Porter JR, Spence DC, Esparza E, Cole DC, Huson FR (2002) A desktop magnetic resonance imaging system. Magn Reson Mater Phy 13(3):177–185CrossRefGoogle Scholar
  15. 15.
    Dueck G, Scheuer T (1990) Threshold accepting: a general purpose optimization algorithm appearing superior to simulated annealing. J Comput Phys 90(1):161–175CrossRefGoogle Scholar
  16. 16.
    Kirkpatrick S, Gelatt CD, Vecchi MP (1983) Optimization by simulated annealing. Science 220(4598):671–680CrossRefPubMedGoogle Scholar
  17. 17.
    Hidalgo-Tobon SS (2010) Theory of gradient coil design methods for magnetic resonance imaging. Concepts Magn Reson A 36(4):223–242CrossRefGoogle Scholar
  18. 18.
    Turner R (1993) Gradient coil design: a review of methods. Magn Reson Imaging 11(7):903–920CrossRefPubMedGoogle Scholar
  19. 19.
    Golay MJE (1958) Field homogenizing coils for nuclear spin resonance instrumentation. Rev Sci Instrum 29(4):313–315CrossRefGoogle Scholar
  20. 20.
    Tanner JE (1965) Pulsed field gradients for NMR spin-echo diffusion measurements. Rev Sci Instrum 36:1086–1087CrossRefGoogle Scholar
  21. 21.
    Carr HY, Purcell EM (1954) Effects of diffusion on free precession in nuclear magnetic resonance experiments. Phys Rev 94(3):630–638CrossRefGoogle Scholar
  22. 22.
    Aksel B, Marinelli L, Collick BD, Von Morze C, Bottomley PA, Hardy CJ (2007) Local planar gradients with order-of-magnitude strength and speed advantage. Magn Reson Med 58(1):134–143CrossRefPubMedPubMedCentralGoogle Scholar
  23. 23.
    Caparelli EC, Tomasi D, Panepucci H (1999) Shielded biplanar gradient coil design. Magn Reson Imaging 9(5):725–731CrossRefGoogle Scholar
  24. 24.
    Martens MA, Petropoulos LS, Brown RW, Andrews JH, Morich MA, Patrick JL (1991) Insertable biplanar gradient coils for magnetic resonance imaging. Rev Sci Instrum 62(11):2639–2645CrossRefGoogle Scholar
  25. 25.
    Tomasi D, Caparelli EC, Panepucci H, Foerster B (1999) Fast optimization of a biplanar gradient coil set. J Magn Reson 140(2):325–339CrossRefPubMedGoogle Scholar
  26. 26.
    Romeo F, Hoult DI (1984) Magnet field profiling—analysis and correcting coil design. Magn Reson Med 1(1):44–65CrossRefPubMedGoogle Scholar
  27. 27.
    Sekihara K, Matsui S, Kohno H (1985) NMR imaging for magnets with large nonuniformities. IEEE Trans Med Imaging MI-4(4):193–199CrossRefGoogle Scholar
  28. 28.
    Kartäusch R, Wintzheimer S, Ledwig M, Jakob PM, Fidler F (2011) Compact magnet design with significantly reduced eddy currents based on ferrite material. In: International conference on magnetic resonance microscopy (ICMRM), Beijing, China, p 202Google Scholar
  29. 29.
    Mispelter J, Lupu M, Briguet A (2006) NMR Probeheads for Biophysical and Biomedical Experiments. Imperial College Press, LondonCrossRefGoogle Scholar
  30. 30.
    Grafendorfer T, Conolly S, Sullivan C, Macovski A, Scott G (2005) Can Litz coils benefit SNR in remotely polarized MRI? In: Proceedings of the 13th annual meeting of ISMRM, Miami Beach, FL, USA, p 923Google Scholar
  31. 31.
    do Nascimento GC, de Souza RE, Engelsberg M (1989) A simple, ultralow magnetic field NMR imaging system. J Phys E Sci Instrum 22(9):774–779CrossRefGoogle Scholar
  32. 32.
    Savukov I, Karaulanov T, Wurden C, Schultz L (2013) Non-cryogenic ultra-low field MRI of wrist–forearm area. J Magn Reson 233:103–106CrossRefPubMedPubMedCentralGoogle Scholar
  33. 33.
    Savukov I, Karaulanov T, Castro A, Volegov P, Matlashov A, Urbatis A, Gomez J, Espy M (2011) Non-cryogenic anatomical imaging in ultra-low field regime: hand MRI demonstration. J Magn Reson 211:101–108CrossRefPubMedPubMedCentralGoogle Scholar
  34. 34.
    LaPierre C, Sarracanie M, Waddington DEJ, Rosen MS (2015) A single channel spiral volume coil for in vivo imaging of the whole human brain at 6.5 mT. In: Proceedings of the 23rd annual meeting of ISMRM, Toronto, ON, Canada, p 1793Google Scholar
  35. 35.
    Warf BC (2005) Hydrocephalus in Uganda: the predominance of infectious origin and primary management with endoscopic third ventriculostomy. J Neurosurg 102(1 Suppl):1–15PubMedGoogle Scholar
  36. 36.
    Mandell JG, Kulkarni AV, Warf BC, Schiff SJ (2015) Volumetric brain analysis in neurosurgery: part 2. Brain and CSF volumes discriminate neurocognitive outcomes in hydrocephalus. J Neurosurg Pediatr 15(2):125–132CrossRefPubMedGoogle Scholar
  37. 37.
    Savukov I, Karaulanov T (2013) Magnetic-resonance imaging of the human brain with an atomic magnetometer. Appl Phys Lett 103(4):43703CrossRefPubMedGoogle Scholar

Copyright information

© ESMRMB 2016

Authors and Affiliations

  • Steffen Lother
    • 1
    Email author
  • Steven J. Schiff
    • 2
  • Thomas Neuberger
    • 3
    • 4
  • Peter M. Jakob
    • 1
    • 5
  • Florian Fidler
    • 1
  1. 1.Research Center Magnetic-Resonance-Bavaria (MRB)WürzburgGermany
  2. 2.Departments of Engineering Science and Mechanics, Neurosurgery, and Physics, Center of Neural EngineeringPenn State UniversityUniversity ParkUSA
  3. 3.High Field MRI Facility, Huck Institutes of the Life SciencesPenn State UniversityUniversity ParkUSA
  4. 4.Department of Biomedical EngineeringPenn State UniversityUniversity ParkUSA
  5. 5.Department for Experimental Physics 5 (Biophysics)University of WuerzburgWürzburgGermany

Personalised recommendations