Simultaneous electroencephalography-functional MRI at 3 T: an analysis of safety risks imposed by performing anatomical reference scans with the EEG equipment in place

J Magn Reson Imaging. 2012 Mar;35(3):561-71. doi: 10.1002/jmri.22843. Epub 2011 Oct 14.


Purpose: 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.

Materials and 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.

Conclusion: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Body Composition
  • Electrocardiography / instrumentation
  • Electrodes
  • Electroencephalography / instrumentation*
  • Electromyography / instrumentation
  • Equipment Safety
  • Hot Temperature
  • Humans
  • Magnetic Resonance Imaging / instrumentation*
  • Patient Safety*
  • Phantoms, Imaging