Jens Matthias Theysohn MD, Presenter: Nothing to Disclose

Oliver Kraff MSc, Abstract Co-Author: Nothing to Disclose

Marcus Gerwig, Abstract Co-Author: Nothing to Disclose

Dagmar Timmann, Abstract Co-Author: Nothing to Disclose

Franz Schmitt, Abstract Co-Author: Employee, Siemens AG

Elke Ruth Gizewski, Abstract Co-Author: Nothing to Disclose

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

Susanne C. Ladd MD, Abstract Co-Author: Nothing to Disclose

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

MRI including high field (up to 3 Tesla) is known as a safe diagnostic imaging procedure without harmful long-term effects. Transient side effects are reported more frequently at higher fields; in particular, some subjects report a subjective postural instability after the examination, which this study assesses quantitatively at 7T.

Fifty healthy volunteers (35m, 15f, mean age 33y) underwent a Romberg’s test before, 2-5 min after, and 15 min after 7T MRI, at different exposure scenarios (30 min each): (1) complete (B0, gradients, RF); (2) B0 with gradients, without RF; (3) neither RF nor gradient switching (subgroup n=20); (4) control without MR exposure; in addition: (5) only movement into the center of the magnet and back out (0 min scan time, subgroup n=20). Volunteers were asked to stand on a 20 cm thick foam cushion with feet close together and with eyes open or closed to minimize information from the proprioceptive and/ or visual system and to maximize use of the vestibular system. An ultrasound real-time measuring system recorded the 3D position and sway path length of a transmitter fixated to the lumbar spine during 30s. Data were compared for different time points, MR settings, and eyes open or closed.

Sway path length of the lumbar spine showed no significant differences before, 2-5 min after and 15 min after any scenario when eyes were open. With eyes closed significant changes occurred after (1) complete exposure at 2 min versus baseline and normalized after 15 min. A similar tendency (borderline significance) was also apparent for exposure with gradients but no RF (2). Significant effects were noted neither in the subgroup without RF and without gradients (3), nor in the control group (4) nor in the setting (5).

Exposure to a head 7 Tesla MRI causes only a temporary dysfunction or over-compensation of the vestibular system. B0 (including dB0/dt during table movement) and gradients seem to have an influence on postural stability, whereas RF does not seem to exhibit a significant influence. Further studies are needed to differentiate between the effects of B0, dB0/dt and the gradients.

Evaluating temporary side effects of 7 Tesla MRI is mandatory before transferring it into diagnostic routine. This study supports its safeness and renders deeper insight into underlying mechanisms.

Theysohn, J, Kraff, O, Gerwig, M, Timmann, D, Schmitt, F, Gizewski, E, Ladd, M, Ladd, S, Bitz, A, Influence of 7 Tesla Brain MRI on Postural Stability.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12038281.html