• Jürgen Hennig
Part of the Medical Radiology book series (MEDRAD)


MR is accompanied to exposure to three different mechanisms of interaction: the main magnetic field, switched gradient fields used for spatial encoding, and the radiofrequency fields used for signal transmission. The physical mechanisms are identical to those at conventional MR. Exposure levels in UHF-MR nevertheless reach values of concern necessitating appropriate measures to ensure safety of patients, volunteers, and operating and technical personnel. This especially applies to energy deposition by radiofrequency fields. Specific absorption rate increases with frequency, at UHF-MR the problem is exacerbated by the necessity to use parallel transmission to generate homogeneous excitation. Gradient-induced peripheral nerve stimulation depends on local changes of the magnetic field, and not on the main field strength. Secondary effects like induced currents when moving in the field do become appreciable at UHF-MR and lead to sensory effects like vertigo and nausea. For both of these exposure categories the physical mechanisms are basically known, serious disagreement arises about safety margins when defining exposure levels for safe application especially with respect to induced currents. The most contentious issue relates to safety of the main field itself. There are numerous reports about interactions of magnetic fields with living tissues, but so far no known biological effects have been identified as a definite health risk at currently achievable field strengths. From a scientific point of view this seems to be good news for the safe applications of UHF-MR, but translating this lack of evidence into regulatory guidelines is a tricky and contentious issue with potential serious consequences for the field.


Magnetic Field Static Magnetic Field Magnetic Resonance Scanner Specific Absorption Rate Peripheral Nerve Stimulation 
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  1. Andrä W (2007) Magnetism in medicine. Wiley-VCH, WeinheimGoogle Scholar
  2. CEC (Commission of the European Communities) (2000) Communication from the commission on the precautionary principle. CEC, Brussels, 02.02.2000, COM(2000) 1Google Scholar
  3. Crozier S, Trakic A et al (2007) Numerical study of currents in workers induced by body-motion around high-ultrahigh field MRI magnets. J Magn Reson Imaging 26:1261–1277CrossRefGoogle Scholar
  4. Directive 2004/40/EC of the European Parliament and of the Council of 29 April 2004Google Scholar
  5. Feychting M (2005) Health effects of static magnetic fields—a review of the epidemiological evidence. Prog Biophys Mol Biol 87(2–3):241–246PubMedCrossRefGoogle Scholar
  6. Foster KR, Vecchia P, Repacholi MH (2000) Risk management. Science and the precautionary principle. Science 288(5468):979–981PubMedCrossRefGoogle Scholar
  7. Glover PM (2009) Interaction of MRI field gradients with the human body. Phys Med Biol 54(21):R99–R115PubMedCrossRefGoogle Scholar
  8. Glover PM, Bowtell R (2007) Measurement of electric fields due to time-varying magnetic field gradients using dipole probes. Phys Med Biol 52(17):5119–5130PubMedCrossRefGoogle Scholar
  9. Glover PM, Cavin I et al (2007a) Magnetic-field-induced vertigo: a theoretical and experimental investigation. Bioelectromagnetics 28(5):349–361PubMedCrossRefGoogle Scholar
  10. Glover PM, Eldeghaidy S et al (2007b) Measurement of visual evoked potential during and after periods of pulsed magnetic field exposure. J Magn Reson Imaging 26:1353–1356PubMedCrossRefGoogle Scholar
  11. ICNIRP (1994) Guidelines on limits of exposure to static magnetic-fields. Health Phys 66(1):100–106Google Scholar
  12. ICNIRP (1998) Guidelines for limiting exposure to time-varying electric, magnetic, electromagnetic fields (up to 300 GHz) (vol 74, p 494, 1998). Health Phys 75(4):442–442Google Scholar
  13. ICNIRP, P Int Comm Non-Ionizing Radiation (2009) Guidelines on limits of exposure to static magnetic fields. Health Phys 96(4):504–514CrossRefGoogle Scholar
  14. ICNIRP, R Int Commission NonIonizing (2002) General approach to protection against non-ionizing radiation. Health Phys 82(4):540–548CrossRefGoogle Scholar
  15. ICNIRP, R Int Commission Nonionizing (2009) ICNIRP statement on the guidelines for limiting exposure to time-varying electric, magnetic, and electromagnetic fields (up to 300 GHz). Health Phys 97(3):257–258CrossRefGoogle Scholar
  16. IEC (2008) Standard IEC 60601-2-33: Medical electrical equipment, International Electrotechnical CommissionGoogle Scholar
  17. Kinouchi Y, Yamaguchi H et al (1996) Theoretical analysis of magnetic field interactions with aortic blood flow. Bioelectromagnetics 17(1):21–32PubMedCrossRefGoogle Scholar
  18. Kirschwink JL (1997) Magnetoreception—homing in on vertebrates. Nature 390(6658):339–340CrossRefGoogle Scholar
  19. Miyakoshi J (2005) Effects of static magnetic fields at the cellular level. Prog Biophys Mol Biol 87(2–3):213–223PubMedCrossRefGoogle Scholar
  20. Reilly JP (1989) Peripheral-nerve stimulation by induced electric currents—exposure to time-varying magnetic-fields. Med Biol Eng Comput 27(2):101–110PubMedCrossRefGoogle Scholar
  21. Saunders R (2005) Static magnetic fields: animal studies. Prog Biophys Mol Biol 87(2–3):225–239PubMedCrossRefGoogle Scholar
  22. Schenck JF (2005) Physical interactions of static magnetic fields with living tissues. Prog Biophys Mol Biol 87(2–3):185–204PubMedCrossRefGoogle Scholar
  23. Simon MD, Geim AK (2000) Diamagnetic levitation: flying frogs and floating magnets (invited). J Appl Phys 87(9):6200–6204CrossRefGoogle Scholar
  24. Tenforde TS (2005) Magnetically induced electric fields and currents in the circulatory system. Prog Biophys Mol Biol 87(2–3):279–288PubMedCrossRefGoogle Scholar
  25. WHO (2006) Environmental health criteria 232: static fields. Geneva, Switzerland, ISBN 92-4-157232-9Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  1. 1.Universität FreiburgFreiburgGermany

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