title: Simultaneous electroencephalography-functional MRI at 3 T: an analysis of safety risks imposed by performing anatomical reference scans with the EEG equipment in place.
abstract: OBJECTIVE
  To describe heating effects to be expected in simultaneous electroencephalography (EEG) and magnetic resonance imaging (MRI) when deviating from the EEG manufacturer's instructions; to test which anatomical MRI sequences have a sufficiently low specific absorption rate (SAR) to be performed with the EEG equipment in place; and to suggest precautions to reduce the risk of heating.
  
  
  METHODS
  Heating was determined in vivo below eight EEG electrodes, using both head and body coil transmission and sequences covering the whole range of SAR values.
  
  
  RESULTS
  Head transmit coil: temperature increases were below 2.2°C for low SAR sequences, but reached 4.6°C (one subject, clavicle) for high SAR sequences; the equilibrium temperature T(eq) remained below 39°C. Body transmit coil: temperature increases were higher and more frequent over subjects and electrodes, with values below 2.6°C for low SAR sequences, reaching 6.9°C for high SAR sequences (T8 electrode) with T(eq) exceeding a critical level of 40°C.
  
  
  CONCLUSIONS
  Anatomical imaging should be based on T1-weighted sequences (FLASH, MPRAGE, MDEFT) with an SAR below values for functional MRI sequences based on gradient echo planar imaging. Anatomical sequences with a high SAR can pose a significant risk, which is reduced by using head coil transmission.
authors: Brain Imaging Center (BIC), Goethe University Frankfurt am Main, Frankfurt am Main, Germany. noeth@med.uni-frankfurt.de
authors: Ulrike
authors: U
authors: Nöth
authors: Helmut
authors: H
authors: Laufs
authors: Robert
authors: R
authors: Stoermer
authors: Ralf
authors: R
authors: Deichmann
mesh_terms: D001823:Body Composition; D004562:Electrocardiography / Q000295:instrumentation; D004566:Electrodes; D004569:Electroencephalography / Q000295:instrumentation*; D004576:Electromyography / Q000295:instrumentation; D004869:Equipment Safety; D006358:Hot Temperature; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D061214:Patient Safety; D019047:Phantoms, Imaging