What risk is associated with rotational force in an MRI?

The risk associated with rotational force in an MRI pertains to the torque on an implant. When a patient with an implant, such as a pacemaker or any other ferromagnetic device, enters the magnetic field of the MRI machine, the strong magnetic forces can exert torque on the implant. This can potentially lead to displacement or damage to the implant, which may cause serious harm to the patient. The rotational force created by the magnetic field can alter the position of the device, disrupt its function, or lead to injury to surrounding tissue.

In contrast, while other risks like missile effect or peripheral nerve stimulation are valid concerns in MRI, they do not specifically address the issue of rotational forces acting on implants. The missile effect refers to the potential of ferromagnetic objects being attracted into the MRI scanner, while peripheral nerve stimulation is related to the effects of the gradients during scans. The antenna effect involves the generation of heating in conductive materials within the magnetic field, which is also a separate concern from the torque induced on implants. Thus, the torque on an implant is the most relevant risk resulting from rotational forces in an MRI scenario.