Personal exposure to static and time-varying magnetic fields during MRI system test procedures

J Magn Reson Imaging. 2009 Nov;30(5):1223-8. doi: 10.1002/jmri.21952.

Abstract

Purpose: To assess personal time-weighted average (TWA) static magnetic field and time-varying magnetic field exposure for several system testing tasks routinely conducted by engineers at an MRI manufacturing plant.

Materials and methods: Personal exposure was measured using a personal dosimeter that measured B and dB/dt in all three orthogonal directions with a 1 Hz frequency. TWA exposure was calculated and random effects and linear mixed effects models were used to assess exposure levels and variability.

Results: Whereas full-body peak (2T) and TWA (200 mT/8 h) exposure limits for the static magnetic field originally proposed by ICNIRP were not exceeded, time-varying magnetic field peaks (dB/dt) did exceed the proposed threshold value (767.9 mT/s) suggested by IEEE on several occasions at the 3.0 Tesla (T) whole-body cylindrical system.

Conclusion: TWA exposure levels are well below the proposed limit values, but peak exposure limits are exceeded during certain procedures performed on 1.0T to 3.0T systems.

MeSH terms

  • Calibration
  • Electromagnetic Fields*
  • Humans
  • Magnetic Resonance Imaging / methods*
  • Occupational Exposure
  • Radiation Dosage
  • Radiation Monitoring / instrumentation
  • Radiation Monitoring / methods
  • Radiation Protection / instrumentation
  • Radiation Protection / methods
  • Radiometry / methods*
  • Reproducibility of Results
  • Risk Assessment
  • Time Factors