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Measurements of occupational exposure to switched gradient and spatially‐varying magnetic fields in areas adjacent to 1.5T clinical MRI systems
Author(s) -
Riches Sophie F.,
Collins David J.,
CharlesEdwards Geoffrey D.,
Shafford Jonathan C.,
Cole Jonathan,
Keevil Stephen F.,
Leach Martin O.
Publication year - 2007
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.21139
Subject(s) - scanner , directive , magnetic resonance imaging , european union , magnetic field , magnet , magnetostatics , computer science , medicine , physics , radiology , artificial intelligence , business , quantum mechanics , programming language , economic policy
Purpose To determine if magnetic field exposure close to two clinical 1.5T magnetic resonance imaging (MRI) scanners during image acquisition and when moving in the spatially‐varying static magnetic field is compliant with European Union (EU) Directive 2004/40/EC (the Directive). Materials and Methods Using commercially available equipment we measured the magnetic flux density around the scanners during two clinical pulse sequences. The data was compared with frequency‐dependent limits that will limit occupational exposure following transposition of the Directive into national law in 2008. The static magnetic field was measured around the scanners and the exposure from movement within this field was simulated. Results The whole‐body exposure experienced when standing close to the face of the magnet exceeds the limits in the Directive on the two scanners tested during clinical sequences. Simulation of movement toward the scanner shows that speeds must be restricted to 1/5 of normal walking speed to comply with the Directive. Conclusion EU Directive 2004/40/EC will have a major impact on the current use and future development of MRI due to limitations on exposure to time‐varying gradient fields and movement within the spatially‐varying static field. This will make interventional work impossible and routine MRI use impracticable in Europe. J. Magn. Reson. Imaging 2007;26:1346–1352. © 2007 Wiley‐Liss, Inc.