Neurocognitive functioning is modulated when exposed to movement-induced TVMF within an SMF of a 7 T MRI scanner. Domains that were affected include attention/concentration and visuospatial orientation. Further studies are needed to better understand the mechanisms and possible practical safety and health implications of these acute neurocognitive effects.

We assessed postural body sway performance after exposure to movement induced time-varying magnetic fields in the static magnetic stray field in front of a 7 Tesla (T) magnetic resonance imaging scanner. Using a double blind randomized crossover design, 30 healthy volunteers performed two balance tasks (i.e., standing with eyes closed and feet in parallel and then in tandem position) after standardized head movements in a sham, low exposure (on average 0.24 T static magnetic stray field and 0.49 T·s(-1) time-varying magnetic field) and high exposure condition (0.37 T and 0.70 T·s(-1)). Personal exposure to static magnetic stray fields and time-varying magnetic fields was measured with a personal dosimeter. Postural body sway was expressed in sway path, area, and velocity. Mixed-effects model regression analysis showed that postural body sway in the parallel task was negatively affected (P < 0.05) by exposure on all three measures. The tandem task revealed the same trend, but did not reach statistical significance. Further studies are needed to investigate the possibility of independent or synergetic effects of static magnetic stray field and time-varying magnetic field exposure. In addition, practical safety implications of these findings, e.g., for surgeons and others working near magnetic resonance imaging scanners need to be investigated.

Neurocognitive effects were only observed when simultaneously exposed to SMF and TVMF from a 7 T MRI scanner. Therefore, exposure to TVMF seems essential in eliciting the neurocognitive effects in our present study and, presumably, previous experiments.

The ‘complex neural pulse’TM (CNP) is a neuromodulation protocol employing weak pulsed electromagnetic fields (PEMF). A pioneering paper reported an analgesic effect in healthy humans after 30 minutes of CNP-stimulation using three nested whole head coils. We aimed to devise and validate a stimulator with a novel design entailing a multitude of small coils at known anatomical positions on a head cap, to improve applicability. The main hypothesis was that CNP delivery with this novel device would also increase heat pain thresholds. Twenty healthy volunteers were enrolled in this double-blind, sham-controlled, crossover study. Thirty minutes of PEMF (CNP) or sham was applied to the head. After one week the other treatment was given. Before and after each treatment, primary and secondary outcomes were measured. Primary outcome was heat pain threshold (HPT) measured with thermal quantitative sensory testing. Other outcomes were warmth detection threshold, and aspects of cognition, emotion and motor performance. As hypothesized heat pain threshold was significantly increased after the PEMF stimulation. All other outcomes were unaltered by the PEMF but there was a trend level reduction of cognitive performance after PEMF stimulation as measured by the digit-symbol substitution task. Results from this pilot study suggest that our device is able to stimulate the brain and to modulate its function. This is in agreement with previous studies that used similar magnetic field strengths to stimulate the brain. Specifically, pain control may be achieved with PEMF and for this analgesic effect, coil design does not appear to play a dominant role. In addition, the flexible configuration with small coils on a head cap improves clinical applicability.Trial RegistrationDutch Cochrane Centre NTR1093

Dear Sir, With interest we took note of a review on health effects and safety of Magnetic Resonance Imaging by Drs Ng, Faust and Acharya U, published online on March 30 2010 in the Journal of Medical Systems [1]. As adequately described by the authors there are a wide number of advantages to the use of MRI as a medical imaging modality that have led to improved diagnostic outcomes without the drawbacks of for example the use of X-rays; hence the exponential growth in usage since its first introduction in the late 1970s [2]. Nonetheless, there are several serious drawbacks related to the strong static and time-varying magnetic fields and radiofrequency fields required for scanning which as discussed by the authors require specific safety recommendations.Unfortunately, set out as a review of current knowledge of adverse health effects and current safety issues related to MRI environments for both patients and staff members this review fails to achieve its aim. Surprisingly, the most recent non-self citation reference to peer-reviewed work is from 2007 despite ongoing research since then. As such, it is no surprise that the safety recommendations provided by the authors focus on prevention of accidents due to ferromagnetic objects and implants, (local) tissue heating and reduction of acoustic noise, which were the only notable risks associated with MRI identified at the end of the previous century [3].However, since the publications cited by the authors an additional body of work (of which the first peer-reviewed papers were in fact already published in the period supposedly covered in the review) into acute transient adverse effects related to exposure to the static and time-varying magnetic fields present in, but also surrounding MRI systems has emerged. Controlled human trials [4][5][6] have provided evidence that visual perception and visuo-motor performance are negatively affected during movement (of the head) in the heterogeneous static magnetic stray field surrounding MR systems. A more recent study has also shown that different cognitive domains can also be affected by time-varying magnetic fields [7]. In line with proposed biological mechanisms for these effects [8,9] no effects were observed within the homogeneous magnet bore, where patients are located during scanning [10] nor were effects on cognition measurable immediately after exposure had ended [11]. However, recent data from a controlled trial using transcranial magnetic stimulation (TMS) does suggest a transient alteration in cortical excitability after undergoing an MRI scan and exposure has ended [12]. Although a threshold level seems to exist for at least some of the acute effects [13], effects could already be measured well below the 2 T and 6 Ts −1 limits mentioned in this review (although appropriate limit values would instead have been the most recent ICNIRP guidelines [14]). Field surveys have further shown that MR engineers [15] and nurses [16] routinely working with MRI scanners regularly experience adverse transient effects including