EFFECT OF MAGNETIC-RESONANCE-IMAGING ON IMPLANTABLE EYELID WEIGHTS

Implanted upper eyelid gold weights are used to prevent corneal injury in patients with facial nerve paralysis. Some of these individuals re quire postoperative radiographic surveillance for recurrent lateral sk ull base disease. Magnetic resonance imaging (MRI) provides the most a ccurate radiologic assessment; however, there is concern about the saf ety of performing MRI in patients with any metallic implant. Potential risks include local tissue heating and implant migration. Gold weight s of 0.8 and 1.4 g were placed in an open chamber and were exposed to a magnetic field of 1.5 T. There was no measurable motion or displacem ent of the weights. The results were similar in 6 rats in which gold w eights were subcutaneously implanted. Additionally, histologic examina tion of the implant sites revealed no adverse tissue effects attributa ble to MRI-generated heating of the implants. When carbon steel implan ts in the rat model were subjected to the magnetic field, there was no displacement of the implants and no adverse tissue effects were noted , despite the fact that a carbon steel implant in an open chamber demo nstrated significant migration. The absence of motion of the gold weig ht implants combined with the lack of adverse tissue effects suggests the relative safety of performing MRI in patients with previously plac ed gold weights as upper eyelid implants.