title: Does assessment of personal exposure matter during experimental neurocognitive testing in MRI-related magnetic fields?
abstract: OBJECTIVE
  To determine whether the use of quantitative personal exposure measurements in experimental research would result in better estimates of the associations between static and time-varying magnetic field exposure and neurocognitive test performance than when exposure categories were based solely on distance to the magnetic field source.
  
  
  METHODS
  In our original analysis, based on distance to the magnet of a 7 T MRI scanner, an effect of exposure to static magnetic fields was observed. We performed a sensitivity analysis of test performance on a reaction task and line bisection task with different exposure measures that were derived from personal real-time measurements.
  
  
  RESULTS
  The exposure measures were highly comparable, and almost all models resulted in significant associations between exposure to time-varying magnetic fields within a static magnetic field and performance on a reaction and line bisection task.
  
  
  CONCLUSIONS
  In a controlled experimental setup, distance to the bore is a good proxy for personal exposure when placing subjects at fixed positions with standardized head movements in the magnetic stray fields of a 7 T MRI. Use of a magnetic field dosimeter is, however, important for estimating quantitative exposure response associations.
authors.affiliation: Institute for Risk Assessment Sciences, Division of Environmental Epidemiology, Utrecht University, Utrecht, The Netherlands.
authors.forename: Lotte E
authors.initials: LE
authors.lastname: van Nierop
authors.forename: Yvette
authors.initials: Y
authors.lastname: Christopher-de Vries
authors.forename: Pauline
authors.initials: P
authors.lastname: Slottje
authors.forename: Hans
authors.initials: H
authors.lastname: Kromhout
mesh_terms: D000328:Adult; D003071:Cognition / Q000502:physiology* / Q000528:radiation effects; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004781:Environmental Exposure / Q000032:analysis*; D005260:Female; D006801:Humans; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging; D008297:Male; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: dosimeter; magnetic resonance imaging; neurocognitive tasks; personal exposure; static magnetic fields; time-varying magnetic fields