Analysis and measurements of magnetic field exposures for healthcare workers in selected MR environments

Fuentes, M. A., Trakic, A., Wilson, S.J. and Crozier, S. (2008) Analysis and measurements of magnetic field exposures for healthcare workers in selected MR environments. IEEE Transactions on Biomedical Engineering, 55 4: 1355-1364.


Author Fuentes, M. A.
Trakic, A.
Wilson, S.J.
Crozier, S.
Title Analysis and measurements of magnetic field exposures for healthcare workers in selected MR environments
Journal name IEEE Transactions on Biomedical Engineering  (ERA 2012 Listed)    (ERA 2010 Rank A*)   Check publisher's open access policy
Publication date 2008-04
Sub-type Article
Year available 2008
DOI 10.1109/TBME.2007.913410
Volume number 55
Issue number 4
ISSN 0018-9294
Start page 1355
End page 1364
Total pages 10
Editor Principe, J,C.
Place of publication USA
Publisher IEEE
Collection year 2009
Language eng
Subject C1
0903 Biomedical Engineering
970109 Expanding Knowledge in Engineering
730299 Public health not elsewhere classified
Abstract There are concerns about workers repeatedly exposed to magnetic fields exceeding regulatory limits with respect to modern magnetic resonance imaging (MRI). As a result, there is need for an ambulatory magnetic field dosimeter capable of measuring these fields in and around an MRI scanner in order to evaluate the regulatory guidelines and determine any underlying exposure risks. This study presents results of tri-axial measurements using an ambulatory magnetic field dosimeter worn by workers during normal working shifts. We recorded and analyzed magnetic field exposures in and around 1.5 T, 2 T, and 4 T magnets during routine patient procedures. The data was integrated and averaged over time and evaluated against the latest exposure standards. Time-varying magnetic fields occur when individuals move through spatially non-uniform static magnetic fields or during gradient-pulsed magnetic fields or a combination of both. Our previous numerical analysis shows that at certain positions surrounding the MRI scanner ends, such fields may induce current densities and electric fields that may exceed the relevant EU, ICNIRP, and IEEE standards. A high-speed acquisition version of the dosimeter measured gradient-pulsed fields at positions accessible by MRI workers near the scanner ends, and the results were evaluated and compared against the numerical simulations and the standards. Our measurements confirm that workers can be exposed to magnetic fields exceeding the guidelines at positions near the gradient coil ends during clinical imaging and a high degree of correlation exists with the numerical results. While the time-weighted average magnetic field exposures in 1.5 T, 2 T, and 4 T were all within the regulatory limits during static magnetic field measurements, the peak limits for the head can be exceeded in some circumstances. This study presents a small number of routine shifts of data that provide indicative results of magnetic field exposure in real situations.
Keyword Dosimeter
magnetic resonance imaging
coordination
Walking
Body
Head
Ghz
Q-Index Code C1
Q-Index Status Confirmed Code

 
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