Electric and magnetic fields in a magnetic resonance imaging facility: measurements and exposure assessment procedures.
Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Purchase Order Report 9239540, 1994 Feb; :1-100
A pilot study was conducted to test protocols for assessing exposure to magnetic and electric fields among workers at magnetic resonance imaging (MRI) facilities. Static magnetic fields, pulsed gradient fields, pulsed radiofrequency electric and magnetic fields, and extremely low frequency, very low frequency, and low frequency magnetic fields were measured in an MRI facility. Data were captured at 5 second intervals over a period sufficient to capture three wave forms at a measurement location. Hall effect sensors were used to measure the static field, and air core induction coils were used to measure the power frequency magnetic fields. At MRI personnel work stations, the measured static fields ranged from 160 millitesla (mT) at the magnet face to 1.5mT at the console, where the operator spends most of his time. The static field measurements in the facility corresponded well with the contours provided by the system manufacturer, confirming that static field exposures can be estimated by combining manufacturers' data with time/motion analysis. The use of a bar code scanning system was evaluated for recording personnel locations in the facility. Time spent near the magnetic face clearly dominates the exposure estimates. The author suggests that additional study be done to compare the time motion estimates of exposure with dosimeter measurements, to characterize gradient fields for different imaging protocols, and to evaluate the use of MRI facility records, such as procedure log books, to estimate exposures.
NIOSH-Contract; Magnetic-fields; Health-care-personnel; Radiation-exposure; Electromagnetic-radiation; Electrical-fields; Occupational-exposure; Nonionizing-radiation
Final Contract Report
NTIS Accession No.
National Institute for Occupational Safety and Health
T. Dan Bracken, Inc.