Abstract
Static electric and magnetic fields are permanently present in the environment. Whereas the static electric field is associated with the presence of fixed electrical charges, the magnetic field is due to the physical movement of electrical charges. Unlike the other categories of fields covered in this work, static fields do not vary over time.
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Notes
- 1.
According to the relation: B = µH, where µ corresponds to the absolute permeability of the material or medium, µ = µ0µr where µr = 1 in vacuum, it is the relative permeability (compared to µ0) and µ0 = 4π × 10−7 USI.
- 2.
A magnetic levitation train was brought into service in Shanghai in 2004 and another is planned in Japan around 2025, but the costs and constraints associated with this mode of transport mean its use is quite limited.
- 3.
For example, a high field MRI is currently being installed at the Neurospin brain research centre (CEA Saclay). This system generates 11.7 T, i.e. 234,000 times the Earth’s field. With the field increase, many technical difficulties can be overcome. Apart from an additional lowering of the temperature of the superconductor (from −269 to −271 °C), it is also necessary to oppose the tendency of the instrument to collapse on itself under the effect of its own magnetic field and to ensure that the noise generated is supportable for the ears of the patients.
- 4.
The whole assembly constitutes the tunnel.
- 5.
Not an ICNIRP recommendation but one of the International Commission for the Safety of Equipment (International Electrotechnical Commission (2002) Safety of magnetic resonance equipment for medical diagnosis. IEC, Geneva: IEC 60601-2-33).
To Find Out More
Institute for magnetic resonance, safety, education and research (IMRSER) http://www.imrser.org/
International Commission on Non-Ionizing Radiation Protection (ICNIRP) (2004) Medical Magnetic Resonance (MR) procedures: protection of patients. Health Physics 87(2):197-216. http://www.icnirp.org/documents/MR2004.pdf
International Commission on Non-Ionizing Radiation Protection (ICNIRP) (2009) Guidelines on limits of exposure to static magnetic fields. Health Physics 96(4):504-14. http://www.icnirp.org/documents/MR2009.pdf
WHO (2006) Environmental Health Criteria Monograph n° 232: Static Fields. WHO, Geneva. http://www.who.int/peh-emf/publications/reports/ehcstatic/en/index.html
WHO (2006) Fact Sheet n° 299: Electromagnetic fields and public health. WHO, Geneva. http://www.who.int/mediacentre/factsheets/fs299/fr/index.html
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© 2012 Springer-Verlag France
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Perrin, A. (2012). MRI and Static Electric and Magnetic Fields. In: Perrin, A., Souques, M. (eds) Electromagnetic Fields, Environment and Health. Springer, Paris. https://doi.org/10.1007/978-2-8178-0363-0_2
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DOI: https://doi.org/10.1007/978-2-8178-0363-0_2
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