Objectives The advances in modern medicine introduced stronger MRI systems up to 9.4 Tesla and a broader area of application. Since the use of stronger imaging systems the amount of reported side effects has increased. Among these symptoms are nausea, dizziness, fatigue sleeplessness, concentration problems and a metallic taste. An earlier study showed also negative effects of movement in the magnetic fields on concentration, visuo-spatial orientation and postural body sway.

Exposure to higher field strengths could have consequences for professions in medical settings where workers are repeatedly exposed. Especially for surgeons and radiologists working close to MRI systems need to maintain a high level of accuracy in performance and cognitive function. Better insight in acute effects on neurocognitive functions, will form a basis for the design of relevant protective and precautionary control measures.

In the present study we try to gain more insight which kind of magnetic fields are responsible for evoking the cognitive effects. We separate between the heterogeneous static magnetic field (SMF) around the scanner and movement induced time-varying magnetic fields (TVMF) within the static magnetic field.

Methods We used a double blind randomised cross over design in which thirty six healthy volunteers underwent four test sessions. The two exposure conditions were near a 7 T MRI system with personal SMF exposure of 1.0 Tesla. In one of these conditions subjects had to make standardised head movements before every task which induced additional TVMF of 2.4 T/s. Of the two corresponding sham conditions (0 T) one was with and one without additional head movements. Cognitive tasks which showed an effect in previous studies were assessed.

Results Results of this study suggests different effects from SMF and TVMF on cognition.