title: Risks and safety aspects related to PET/MR examinations.
abstract: BACKGROUND
  The introduction of positron emission tomography (PET)/magnetic resonance (MR) systems into medical practice in the foreseeable future may not only lead to a gain in clinical diagnosis compared to PET/computed tomography (CT) imaging due to the superior soft-tissue contrast of the MR technology but can also substantially reduce exposure of patients to ionizing radiation. On the other hand, there are also risks and health effects associated with the use of diagnostic MR devices that have to be considered carefully.
  
  
  OBJECTIVE
  This review article summarizes biophysical and biological aspects, which are of relevance for the assessment of health effects related to the exposure of patients to both ionizing radiation in PET and magnetic and electromagnetic fields in MR. On this basis, some considerations concerning the justification and optimization of PET/MR examinations are presented--as far as this is possible at this very early stage.
  
  
  CONCLUSIONS
  Current safety standards do not take into account synergistic effects of ionizing radiation and magnetic and electromagnetic fields. In the light of the developing PET/MR technology, there is an urgent need to investigate this aspect in more detail for exposure levels that will occur at PET/MR systems.
authors.affiliation: Department of Medical and Occupational Radiation Protection, Federal Office for Radiation Protection, Oberschleissheim, Germany. gbrix@bfs.de
authors.forename: Gunnar
authors.initials: G
authors.lastname: Brix
authors.forename: Elke A
authors.initials: EA
authors.lastname: Nekolla
authors.forename: Dietmar
authors.initials: D
authors.lastname: Nosske
authors.forename: Jürgen
authors.initials: J
authors.lastname: Griebel
mesh_terms: D000818:Animals; D000075202:Contraindications; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000009:adverse effects*; D049268:Positron-Emission Tomography / Q000009:adverse effects*; D011839:Radiation, Ionizing; D011840:Radiation, Nonionizing / Q000009:adverse effects; D012306:Risk; D012449:Safety