Biologic effects and potential hazards of nuclear magnetic imaging.

The biologic effects and potential hazards of nuclear magnetic resonance imaging are difficult to quantitate because of the low energy levels currently in use. It is clear, however, that both static and rapidly moving magnetic fields can be a hazard when magnetic field strength is sufficiently high and/or the rapidity of change is fast enough. Additionally, radiofrequency is clearly a hazard when the energy level is high enough. Chronic exposure is less well understood. This new imaging technique presents risks in many ways reminiscent of the previous investigations conducted during the introduction of ultrasound two decades ago.