Evaluation of the additional occupational risk for workers with orthopedic implants in MRI settings.

OBJECTIVE: To provide quantitative information that can aid the relevant authority in deciding whether workers with metallic nonferromagnetic orthopedic implants can work in proximity to magnetic resonance imaging (MRI) scanners, including when the exam is being performed. METHODS: Virtual experiments in which the exposure of workers with and without prostheses is evaluated through numerical simulation of realistic human models, with reference to 4 physical effects: radiofrequency (RF)-induced heating, gradient-induced heating, gradient-induced peripheral nerve stimulation, and mechanical actions related to the Lenz effect. RESULTS: In the presence of the considered implants, the extent of RF-induced heating and of the electric field responsible for peripheral nerve stimulation is low and comparable to what is observed without the prostheses. The extent of gradient-induced heating and Lenz effect, which occur only in the presence of implants, is minimal. CONCLUSION: As long as the body of the worker with passive non-ferromagnetic orthopedic implants remains outside the MRI scanner, the incremental risk posed by the presence of the implants is negligible. The Lenz effect is weak even if the part of the worker's body with an implant enters the scanner bore.