Marc U. Schlamann, Presenter: Nothing to Disclose

Andreas Bitz MSC, Abstract Co-Author: Nothing to Disclose

Marcus Gerwig, Abstract Co-Author: Nothing to Disclose

Oliver Kastrup, Abstract Co-Author: Nothing to Disclose

Adrian Stefan Ringelstein MD, Abstract Co-Author: Nothing to Disclose

Mark E. Ladd PhD, Abstract Co-Author: Nothing to Disclose

Christoph Monninghoff MD, Abstract Co-Author: Nothing to Disclose

Sophia Goericke, Abstract Co-Author: Nothing to Disclose

Stefan Maderwald MSc, Abstract Co-Author: Nothing to Disclose

Aim of this trial was to further investigate the fact that MRI imaging has measurable influence on brains excitability proven by transcranial magnetic stimulation (TMS) (Schlamann et al, Acad. Radiol., 2010). This previous study at 1.5 T and 7 T revealed nearly identical results at both field strength, suggesting that not the static magnetic field is cause for the effects.

Seven male right-handed volunteers (mean age 31.3 years) participated in this study. The examination started with the evaluation of motor threshold (MT) and postexcitatory inhibition (Silent Period (SP)) using transcranial magnetic stimulation over the hand area of the right primary motor cortex. Motor evoked potentials (MEP) were recorded with bipolar surface electrodes attached over the left abductor pollicis brevis muscle. Afterwards the subjects were examined by MRI. Installation of a new MR scanner (Siemens Aera, Siemens HealthCare, Erlangen, Germany) was used to perform the study. Before implementing the magnet, the scanner has been modified to run sequences without static magnetic field and gradient field. With the help of special security passwords, provided by the vendor, it was possible to run sequences in a routine manner without static magnetic field and without the gradients. Therefore only RF was monitored and utilized for imaging. All subjects were positioned prone in the scanner using the 20 channel head-neck coil. The examination consisted of the same series and order of standard spin-echo and gradient-echo sequences (2D and 3D) as used at 1.5T and 7T during the former studies. Hence the total acquisition time for all sequences was 63 minutes. Immediately following MRI examination and 15 minutes thereafter, TMS was performed following the same scheme as it was performed before MRI.  

Immediately after the MR examination all 7 subjects showed a prolongation of SP between 4.3% and 50.3% during TMS. Mean prolongation of the postexitatoric inhibition amounted to 22%. MT was decreased in 6 subjects between 2.2% and 10.9%, and increased in one subject by 2.2%.

RF energy seems to influence cortical excitability of the brain

MR scanners with higher field strength spread more and more. Therefore the discussion on MR safety has gained new momentum.

Schlamann, M, Bitz, A, Gerwig, M, Kastrup, O, Ringelstein, A, Ladd, M, Monninghoff, C, Goericke, S, Maderwald, S, Short Term Effects of RF Energy on Excitability of the Motor Cortex at 0 Tesla MRI.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12038383.html