Cognitive, cardiac, and physiological safety studies in ultra high field magnetic resonance imaging

doi:10.1016/S0730-725X(99)00086-7

Magnetic Resonance Imaging

Volume 17, Issue 10, December 1999, Pages 1407-1416

https://doi.org/10.1016/S0730-725X(99)00086-7 Get rights and content

Abstract

A systematic analysis of the effect of an 8.0 tesla static magnetic field on physiological and/or cognitive function is presented in the normal volunteer and in the swine. A study of ten human subjects revealed no evidence of detectable changes in body temperature, heart rate, respiratory rate, systolic pressure, and diastolic blood pressure after 1 hour of exposure. In addition, no cognitive changes were detected. Important ECG changes were noted which were related both to the position of the subject in the magnet and to the absolute strength of the magnetic field. As such, the ECG tracing at 8 tesla was not diagnostically useful. Nonetheless, all subjects exhibited normal ECG readings both before and following exposure to the 8 tesla field. Cardiac function was also examined in detail in the swine. No significant changes in body temperature, heart rate, left ventricular pressure, left ventricular end diastollic pressure, time rate of change of left ventricular pressure, myocardial stiffness index, cardiac output, systolic volume, troponin, and potassium levels could be detected following 3 h of exposure to a field strength of 8.0 tesla. It is concluded that no short term cardiac or cognitive effects are observed following significant exposure to a magnetic field of up to 8.0 tesla.

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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Original ContributionsCognitive, cardiac, and physiological safety studies in ultra high field magnetic resonance imaging

Abstract

Section snippets

Cardiac sensitivity in the swine

Swine

Discussion

Note in added proof

Acknowledgements

Threshold for physiological effects due to rf and magnetic fields used in NMR imaging

IEEE Trans. Nucl. Sci.

Human exposure to 4.0 Tesla magnetic fields in a whole-body scanner

Med. Phys.

Human magnetic resonance imaging at 8 T

NMR Biomed

Biological responses to static and time-varying magnetic fields

Power deposition in whole body NMR imaging

Med. Phys.

Original Contributions
Cognitive, cardiac, and physiological safety studies in ultra high field magnetic resonance imaging