Original ContributionsCognitive, cardiac, and physiological safety studies in ultra high field magnetic resonance imaging
Section snippets
Cardiac sensitivity in the swine
Twelve, twenty-five to thirty-five kg Yorkshire pigs of either sex were used in this study. Anesthesia was induced with 300 mg of ketamine and 40 mg xylazine given intramuscularly, and 4% inhaled isoflourane. The animals were then intubated and ventilated spontaneously with anesthesia maintained with 1.5 to 2% isofluorane in otherwise 100% oxygen. A catheter-tip micromanometer was inserted via the carotid artery into the left ventricle, a flow-directed thermistor-tip catheter was advanced
Swine
Electrocardiograms obtained at 8 tesla could not be analyzed because of artifacts generated at ultra high magnetic fields. These artifacts have been well described as interfering signals related to interactions between the magnetic field and the instrumentation.6, 11 They were significantly larger than have been reported at 1.5 and 4 tesla and completely obliterated the ECG. Despite the lack of ECG data at 8 tesla, a regular rate and rhythm persisted as documented by the ventricular pressure
Discussion
In the swine, based on the analysis of the parameters measured in the healthy, anesthetized subjects in this study, there is no cardiovascular effect resulting from up to 3 h exposure in a magnetic field of 8 tesla. Similarly, in the human studies, a review of individual and group psychological test data indicate no clinically or statistically significant changes of performance as a result of exposure to the 8 tesla magnetic field. With the exception of a single pre- versus post-exposure
Note in added proof
Outside of this study, four individuals were exposed to a field of >4 tesla during the ramping of the 8 tesla magnet at Magnex Scientific (Abingdon, England). Following exposure to a field of 7.35 tesla for 10 to 20 min, they reported no short or long term effects. Vertigo however, was reported when technicians moved their head rapidly within the bore of the magnet.
Acknowledgements
This work was supported in part by a grant from NIH (HL-45120). The authors thank John Schenck and Robert Bornstein for valuable discussions.
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2020, Magnetic Resonance ImagingCitation Excerpt :More recently, Eryaman et al. [39] used a swine model to measure effects of 10.5 T exposure on blood pressure and heart rate and found an increase of 2–4 mmHg when moving from outside the scanner to isocenter, an effect on the same order as changing positions from lying prone to lying on one's side [40]. Human studies monitoring vital signs during and after exposure to fields up to 9.4 T have found no effect on heart rate [20,24,41], oxygen saturation [24,41], blood pressure [20,24,41], respiration rate [20,24,41], temperature [20,24,41], or pre-vs-post ECG [20,24,41]. Chakeres et al. [41] did find a 3.6 mmHg increase in blood pressure at 8 T, although they noted this was half the size of the change in blood pressure observed when subjects move from supine to sitting position.