Mahsa Fatahi1, Jolanta Karpowicz2, Krzysztof Gryz2, Amirmohammad Fattahi3, Georg Rose4, Oliver Speck5,6,7,8. 1. Department of Biomedical Magnetic Resonance, H65-ZENIT, Otto-von-Guericke-University Magdeburg, Leipziger Street 44, 39120, Magdeburg, Germany. Mahsa.Fatahi@ovgu.de. 2. Laboratory of Electromagnetic Hazards, Central Institute for Labour Protection-National Res. Inst. (CIOP-PIB), Warsaw, Poland. 3. Department of Mechanical Engineering, Imperial College London, London, UK. 4. Institute for Medical Engineering, Otto-von-Guericke University, Magdeburg, Germany. 5. Department of Biomedical Magnetic Resonance, H65-ZENIT, Otto-von-Guericke-University Magdeburg, Leipziger Street 44, 39120, Magdeburg, Germany. 6. Leibniz Institute for Neurobiology, Magdeburg, Germany. 7. Center for Behavioral Brain Sciences, Magdeburg, Germany. 8. German Center for Neurodegenerative Disease, Site Magdeburg, Magdeburg, Germany.
Abstract
OBJECTIVE: To assess the individual exposure to the static magnetic field (SMF) and the motion-induced time-varying magnetic field (TVMF) generated by activities in an inhomogeneous SMF near high and ultra-high field magnetic resonance imaging (MRI) scanners. The study provides information on the level of exposure to high and ultra-high field MRI scanners during research activities. MATERIALS AND METHODS: A three-axis Hall magnetometer was used to determine the SMF and TVMF around human 3- and 7-Tesla (T) MRI systems. The 7-T MRI scanner used in this study was passively shielded and the 3-T scanner was actively shielded and both were from the same manufacturer. The results were compared with the exposure restrictions given by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). RESULTS: The recorded exposure was highly variable between individuals, although they followed the same instructions for moving near the scanners. Maximum exposure values of B = 2057 mT and dB/dt = 4347 mT/s for the 3-T scanner and B = 2890 mT, dB/dt = 3900 mT/s for 7 T were recorded. No correlation was found between reporting the MRI-related sensory effects and exceeding the reference values. CONCLUSIONS: According to the results of our single-center study with five subjects, violation of the ICNIRP restrictions for max B in MRI research environments was quite unlikely at 3 and 7 T. Occasions of exceeding the dB/dt limit at 3 and 7 T were almost similar (30% of 60 exposure scenarios) and highly variable among the individuals.
OBJECTIVE: To assess the individual exposure to the static magnetic field (SMF) and the motion-induced time-varying magnetic field (TVMF) generated by activities in an inhomogeneous SMF near high and ultra-high field magnetic resonance imaging (MRI) scanners. The study provides information on the level of exposure to high and ultra-high field MRI scanners during research activities. MATERIALS AND METHODS: A three-axis Hall magnetometer was used to determine the SMF and TVMF around human 3- and 7-Tesla (T) MRI systems. The 7-T MRI scanner used in this study was passively shielded and the 3-T scanner was actively shielded and both were from the same manufacturer. The results were compared with the exposure restrictions given by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). RESULTS: The recorded exposure was highly variable between individuals, although they followed the same instructions for moving near the scanners. Maximum exposure values of B = 2057 mT and dB/dt = 4347 mT/s for the 3-T scanner and B = 2890 mT, dB/dt = 3900 mT/s for 7 T were recorded. No correlation was found between reporting the MRI-related sensory effects and exceeding the reference values. CONCLUSIONS: According to the results of our single-center study with five subjects, violation of the ICNIRP restrictions for max B in MRI research environments was quite unlikely at 3 and 7 T. Occasions of exceeding the dB/dt limit at 3 and 7 T were almost similar (30% of 60 exposure scenarios) and highly variable among the individuals.
Entities:
Keywords:
Electromagnetic fields; Exposure assessment; Occupational exposure; Static magnetic field; Time-varying field
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