Potential hazards in NMR imaging: heating effects of changing magnetic fields and RF fields on small metallic implants.

To test if changing magnetic fields and radiofrequency fields used in nuclear magnetic resonance imagers could induce electrical currents capable of causing localized tissue heating in metal surgical clips and prostheses, steel surgical clips, copper wire clips, and hip prostheses were exposed to fields greater than those used in the nuclear magnetic resonance imager. Observations indicated that no significant heating should be expected from implanted surgical clips during exposure. The heating of larger metallic implants should be further investigated.