title: Evaluation of occupational exposure in magnetic resonance sites.
abstract: OBJECTIVE
  In an attempt to evaluate the exposure level of magnetic resonance imaging (MRI) workers to static magnetic fields, the isotropic magnetic flux density values were integrated over time to produce the cumulative exposure. To protect occupational staff a further precautionary step is proposed by introducing a weighting function incorporating the limits imposed by the Italian legislation. The results obtained should be reported, at the end of each working day, on a special dose card, in order to record each worker's exposure to the static magnetic field. Moreover, this dose card could be an important tool if long-term effects occur because it provides a complete history of the occupational exposure in an MRI site.
  
  
  METHODS
  To conduct measurements, three Hall-sensor probes were used. The consistency of experimental data, tools and methodologies used was evaluated by performing the Kruskal-Wallis test. Finally, the weighted magnitude of the magnetic flux density was integrated over time to obtain global exposure.
  
  
  RESULTS
  Measurements were performed on different MRI scanners ranging from 0.25 up to 3.0 T. The results obtained were compared with the 200 mT·h, which represents the upper limit of the Italian regulation. In no case was the 200 mT·h per day exposure exceeded: however, when the strength of the magnetic field was >200 mT the weighted function overestimated the exposure, so that it represents a highly precautionary measure taking into account possible acute and long-term effects. In addition, from the data recorded during patient positioning operations by MRI staff the dB/dt curve was obtained.
  
  
  CONCLUSIONS
  The areas obtained from the integral of the weighted static magnetic field strength over time can be indicative of the global exposure of the occupational staff. These values should be reported on a special dose card that could be considered as an important tool if long-term effects occur because it provides a complete history of the occupational exposure in an MRI site.
authors: S.A.S.T.A.S Department-Section of Protezionistica A.S.S.I, University of Messina, Viale Gazzi-Policlinico Universitario, Torre Biologica, 98125, Messina, Italy, gacri@unime.it.
authors: Giuseppe
authors: G
authors: Acri
authors: Barbara
authors: B
authors: Testagrossa
authors: Federica
authors: F
authors: Causa
authors: Maria Giulia
authors: MG
authors: Tripepi
authors: Giuseppe
authors: G
authors: Vermiglio
authors: Raffaele
authors: R
authors: Novario
authors: Liviana
authors: L
authors: Pozzi
authors: Gloria
authors: G
authors: Quadrelli
mesh_terms: D004574:Electromagnetic Fields / Q000009:adverse effects*; D005062:European Union; D017408:Guidelines as Topic; D006801:Humans; D007558:Italy; D008279:Magnetic Resonance Imaging; D016273:Occupational Exposure / Q000331:legislation & jurisprudence; D017751:Safety Management / Q000331:legislation & jurisprudence