TY  - JOUR
A1  - Schlamann, Marc
A1  - Yoon, Min-Suk
A1  - Maderwald, Stefan
A1  - Pietrzyk, Thomas
A1  - Bitz, Andreas
A1  - Gerwig, Marcus
A1  - Forsting, Michael
A1  - Ladd, Susanne C.
A1  - Ladd, Mark E.
A1  - Kastrup, Oliver
T1  - Short term effects of magnetic resonance imaging on excitability of the motor cortex at 1.5T and 7T
JF  - Academic Radiology
N2  - Rationale and Objectives
The increasing spread of high-field and ultra-high-field magnetic resonance imaging (MRI) scanners has encouraged new discussion of the safety aspects of MRI. Few studies have been published on possible cognitive effects of MRI examinations. The aim of this study was to examine whether changes are measurable after MRI examinations at 1.5 and 7 T by means of transcranial magnetic stimulation (TMS).

Materials and Methods
TMS was performed in 12 healthy, right-handed male volunteers. First the individual motor threshold was specified, and then the cortical silent period (SP) was measured. Subsequently, the volunteers were exposed to the 1.5-T MRI scanner for 63 minutes using standard sequences. The MRI examination was immediately followed by another TMS session. Fifteen minutes later, TMS was repeated. Four weeks later, the complete setting was repeated using a 7-T scanner. Control conditions included lying in the 1.5-T scanner for 63 minutes without scanning and lying in a separate room for 63 minutes. TMS was performed in the same way in each case. For statistical analysis, Wilcoxon's rank test was performed.

Results
Immediately after MRI exposure, the SP was highly significantly prolonged in all 12 subjects at 1.5 and 7 T. The motor threshold was significantly increased. Fifteen minutes after the examination, the measured value tended toward normal again. Control conditions revealed no significant differences.

Conclusion
MRI examinations lead to a transient and highly significant alteration in cortical excitability. This effect does not seem to depend on the strength of the static magnetic field.
Y1  - 2010
U6  - http://dx.doi.org/10.1016/j.acra.2009.10.004
SN  - 1076-6332
VL  - 17
IS  - 3
SP  - 277
EP  - 281
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Theysohn, Jens M.
A1  - Kraff, Oliver
A1  - Eilers, Kristina
A1  - Andrade, Dorian
A1  - Gerwig, Marcus
A1  - Timmann, Dagmar
A1  - Schmitt, Franz
A1  - Ladd, Mark E.
A1  - Ladd, Susanne C.
A1  - Bitz, Andreas
T1  - Vestibular effects of a 7 Tesla MRI examination compared to 1.5 T and 0 T in healthy volunteers
JF  - PLoS one
N2  - Ultra-high-field MRI (7 Tesla (T) and above) elicits more temporary side-effects compared to 1.5 T and 3 T, e.g. dizziness or “postural instability” even after exiting the scanner. The current study aims to assess quantitatively vestibular performance before and after exposure to different MRI scenarios at 7 T, 1.5 T and 0 T. Sway path and body axis rotation (Unterberger's stepping test) were quantitatively recorded in a total of 46 volunteers before, 2 minutes after, and 15 minutes after different exposure scenarios: 7 T head MRI (n = 27), 7 T no RF (n = 22), 7 T only B₀ (n = 20), 7 T in & out B₀ (n = 20), 1.5 T no RF (n = 20), 0 T (n = 15). All exposure scenarios lasted 30 minutes except for brief one minute exposure in 7 T in & out B₀. Both measures were documented utilizing a 3D ultrasound system. During sway path evaluation, the experiment was repeated with eyes both open and closed. Sway paths for all long-lasting 7 T scenarios (normal, no RF, only B₀) with eyes closed were significantly prolonged 2 minutes after exiting the scanner, normalizing after 15 minutes. Brief exposure to 7 T B₀ or 30 minutes exposure to 1.5 T or 0 T did not show significant changes. End positions after Unterberger's stepping test were significantly changed counter-clockwise after all 7 T scenarios, including the brief in & out B₀ exposure. Shorter exposure resulted in a smaller alteration angle. In contrast to sway path, reversal of changes in body axis rotation was incomplete after 15 minutes. 1.5 T caused no rotational changes. The results show that exposure to the 7 Tesla static magnetic field causes only a temporary dysfunction or “over-compensation” of the vestibular system not measurable at 1.5 or 0 Tesla. Radiofrequency fields, gradient switching, and orthostatic dysregulation do not seem to play a role.
Y1  - 2014
U6  - http://dx.doi.org/10.1371/journal.pone.0092104
SN  - 1932-6203
VL  - 9
IS  - 3
PB  - PLOS
CY  - San Francisco
ER  -